Transcript
LTC1479 PowerPath Controller for Dual Battery Systems
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DESCRIPTION
FEATURES ■
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The LTC ®1479 is the “heart” of a total power management solution for single and dual battery notebook computers and other portable equipment. The LTC1479 directs power from up to two battery packs and a DC power source to the input of the main system switching regulator. It works in concert with related LTC power management products (e.g. LTC1435, LT ®1511, etc.) to create a total system solution; starting from the batteries and the DC power source, and ending at the input of each of the computer’s complex loads. A system-provided power management µP monitors and actively directs the LTC1479.
Complete Power Path Management for Two Batteries, DC Power Source, Charger and Backup Compatible with Li-Ion, NiCd, NiMH and Lead-Acid Battery Chemistries “3-Diode” Mode Ensures Powers is Available under “Cold Start” Conditions All N-Channel Switching Reduces Power Losses Capacitor and Battery Inrush Current Limited “Seamless” Switching Between Power Sources Independent Charging and Monitoring of Two Battery Packs New, Small Footprint, 36-Lead SSOP Package
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The LTC1479 uses low loss N-channel MOSFET switches to direct power from three main sources. An adaptive current limiting scheme reduces capacitor and battery inrush current by controlling the gates of the MOSFET switches during transitions. The LTC1479 interfaces directly to the LT1510, LT1511 and LT1620/LTC1435 battery charging circuits.
Notebook Computer Power Management Portable Instruments Handheld Terminals Portable Medical Equipment Portable Industrial Control Equipment
, LTC and LT are registered trademarks of Linear Technology Corporation. PowerPath is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATION Dual Battery PowerPathTM Controller System Block Diagram
AC ADAPTER
SW A/B
DCIN
SW C/D
RSENSE
+
SW E/F
BAT1 SW G
CIN
HIGH EFFICIENCY DC/DC SWITCHING REGULATOR (LTC1435/LTC1438 ETC.)
5V
SW H
BAT2 BATTERY CHARGER (LT1510/LT1511/ LT1620/LTC1435)
BACKUP REGULATOR (LT1304)
LTC1479 PowerPath CONTROLLER
STATUS & CONTROL
POWER MANAGEMENT µP
1479 TA01
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LTC1479
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
DCIN, BAT1, BAT2 Supply Voltages .......... – 0.3V to 32V SENSE +, SENSE –, VBAT, V + ..................... – 0.3V to 32V GA, GB, GC, GD, GE, GF, GG, GH .............. – 0.3V to 42V SAB, SCD, SEF, SG, SH ............................ – 0.3V to 32V SW, VGG ................................................... – 0.3V to 42V DCDIV, BDIV ............................................ – 0.3V to 5.5V All Logic Inputs (Note 1).......................... – 0.3V to 7.5V All Logic Outputs (Note 1) ....................... – 0.3V to 7.5V VCC Regulator Output Current ................................ 1mA VCCP Regulator Output Current .............................. 1mA V + Output Current .................................................. 1mA VGG Regulator Output Current ............................ 100µA Operating Temperature LTC1479CG ............................................. 0°C to 70°C LTC1479IG ........................................ – 40°C to 85°C Junction Temperature........................................... 125°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW DCIN
1
36 VBKUP
DCDIV
2
35 BAT1
LOBAT
3
34 BAT2
GA
4
33 BDIV
SAB
5
32 VBAT
GB
6
31 CHGMON
GC
7
30 BATSEL
SCD
8
29 GG
GD
9
28 SG
GE 10
27 GH
SEF 11
26 SH
GF 12 SENSE +
LTC1479CG LTC1479IG
25 DCINGOOD
13
24 DCIN/BAT
SENSE – 14
23 BATDIS
VCC 15
22 3DM
VGG 16
21 CHGSEL
V+
ORDER PART NUMBER
17
20 VCCP
SW 18
19 GND
G PACKAGE (209 mils) 36-LEAD PLASTIC SSOP
TJMAX = 100°C, θJA = 95°C/ W
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS VDCIN = 25V, VBAT1 = 16V, VBAT2 = 12V, TA = 25°C unless otherwise noted. (Note 2) SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supplies VDCIN
DCIN Operating Range
(Mode 1) DCIN Selected
6
28
V
VBAT1
Battery 1 Operating Range
(Mode 5) Battery 1 Selected
6
28
V
VBAT2
Battery 2 Operating Range
(Mode 6) Battery 2 Selected
6
28
V
VBKUP
Backup Operating Range
(Mode 8) Backup Operation
6
28
V
IDCIN
DCIN Operating Current
(Mode 1) DCIN Selected
175
500
µA
IVBAT1
Battery 1 Operating Current
(Mode 5) Battery 1 Selected
150
500
µA
IVBAT2
Battery 2 Operating Current
(Mode 6) Battery 2 Selected
150
500
µA
IVBKUP
Backup Operating Current
(Mode 8) Backup Operation (VBKUP = 6V)
40
100
µA
VCCP
VCCP Regulator Output Voltage
(Modes 1, 5, 6) DCIN, Battery 1 or Battery 2 Selected
●
4.8
6.0
V
VCC
VCC Regulator Output Voltage
(Modes 1, 5, 6) DCIN, Battery 1 or Battery 2 Selected
●
3.3
3.6
3.9
V
VGG
VGG Gate Supply Voltage
(Modes 1, 5, 6) DCIN, Battery 1 or Battery 2 Selected
●
34.0
36.3
40.0
V
VUVLO
UV Lockout Threshold
(Mode 9) No Power, VBATX Falling from 12V
4.0
4.5
5.0
V
VUVLOHYS
UV Lockout Hysteresis
(Mode 9) No Power, VBATX Rising from 1V
0.2
0.5
1.0
V
2
4.0
LTC1479 DC ELECTRICAL CHARACTERISTICS VDCIN = 25V, VBAT1 = 16V, VBAT2 = 12V, TA = 25°C unless otherwise noted. (Note 2) SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
1.190
1.215
1.240
10
35
50
UNITS
DCIN Good Monitor VTHDCDIV
DCDIV Threshold Voltage
(Mode 1) VDCDIV Rising from 1V to 1.5V
VHYSDCDIV DCDIV Hysteresis Voltage
(Mode 1) VDCDIV Falling from 1.5V to 1V
IBIASDCDIV DCDIV Input Bias Current
(Mode 1) VDCDIV = 1.5V
VLODCGD
DCINGOOD Output Low Voltage
(Mode 1) VDCDIV = 1V, IDCINGOOD = 100µA
0
0.1
0.4
V
IPUDCGD
DCINGOOD Pull-Up Current
(Mode 1) VDCDIV = 1.5V, VDCINGOOD = 0V
1
2
6
µA
ILKGDCGD
DCINGOOD Leakage Current
(Mode 1) VDCDIV = 1.5V, VDCINGOOD = 7V
±1
µA V
●
20
V mV nA
Battery Monitor VTHLOBAT
Low-Battery Threshold Voltage
(Modes 5, 6) VBDIV Falling from 1.5V to 1V
VHYSLOBAT Low-Battery Hysteresis Voltage
(Modes 5, 6) VBDIV Rising from 1V to 1.5V
IBIASBDIV
BDIV Input Bias Current
(Modes 5, 6) VBDIV = 1.5V
VLOLOBAT
LOBAT Output Low Voltage
(Modes 5, 6) VBDIV = 1V, ILOBAT = 100µA
ILKGLOBAT
LOBAT Output Leakage Current
(Modes 5, 6) VBDIV = 1.5V, VLOBAT = 7V
RONBATSW Battery Switch ON Resistance
(Modes 5, 6) Each Switch Tested Independently
ILKGBATSW Battery Switch OFF Leakage
(Modes 5, 6) Each Switch Tested Independently
●
1.190
1.215
1.240
10
35
50
0
0.1
20
200
mV nA
0.4
V
±1
µA
800
Ω
±1
µA
5.5 5.2
7.0 7.0
V V
0
0.4
V
400
Gate Drivers VGS(ON)
Gate-to-Source ON Voltage (GA to GF) (Modes 1, 2, 4, 5, 6) IGS = –1µA Gate-to-Source ON Voltage (GG, GH) (Modes 2, 4) IGS = –1µA
5.0 4.5
VGS(OFF)
Gate-to-Source OFF Voltage
(Modes 1, 2, 4, 5, 6) IGS = 100µA
IBSENSE+
SENSE +
Input Bias Current
(Modes 1, 5, 6)
5
15
30
µA
IBSENSE–
SENSE – Input Bias Current
(Modes 1, 5, 6)
5
15
30
µA
VSENSE
Inrush Current Limit Sense Voltage
(Modes 1, 5, 6)
0.15
0.20
0.25
V
IPDSAB
SAB Pull-Down Current
(Modes 5, 6) VSAB = 10V
30
100
300
µA
IPDSCD
SCD Pull-Down Current
(Mode 1) VSCD = 10V
30
100
300
µA
IPDSEF
SEF Pull-Down Current
(Mode 1) VSEF = 10V
30
100
300
µA
IPDSG
SG Pull-Down Current
(Mode 1) VSG = 10V
3
mA
IPDSH
SH Pull-Down Current
(Mode 1) VSH = 10V
3
mA
●
Charge Monitor RONCMON
CHGMON Switch ON Resistance
(Modes 5, 6) Each Switch Tested Independently
ILKGCMON
CHGMON Switch OFF Leakage
(Modes 5, 6) Each Switch Tested Independently
50
150
250
Ω
±1
µA
Digital Inputs VHIDIGIN
Input High Voltage
(Mode 1) All Digital Inputs
●
VLODIGIN
Input Low Voltage
(Mode 1) All Digital Inputs
●
IHIDIGIN
Input Leakage Current
(Mode 1) All Digital Inputs, VDIGINX = 7V
ILODIGIN
Input Leakage Current
(Mode 1) VDIGINX = 0V (Note 3)
IPUDIGIN
Input Pull-Up Current
(Mode 1) VDIGINX = 0V (Note 4)
2
1
V
2
0.8
V
±1
µA
±1
µA
6
µA
3
LTC1479
AC ELECTRICAL CHARACTERISTICS VDCIN = 25V, VBAT1 = 16V, VBAT2 = 12V, TA = 25°C unless otherwise noted. (Note 2) SYMBOL tONGA/GB tONGC/GD tONGE/GF tOFFGA/GB tOFFGC/GD tOFFGE/GF tONGG/GH tOFFGG/GH fOVGG tdLOBAT tdDCINGOOD
PARAMETER Gate A/B Turn-On Time Gate C/D Turn-On Time Gate E/F Turn-On Time Gate A/B Turn-Off Time Gate C/D Turn-Off Time Gate E/F Turn-Off Time Gate G/H Turn-On Time Gate G/H Turn-Off Time VGG Reg Operating Frequency LOBAT Delay Times DCINGOOD Delay Times
CONDITIONS VGS > 3V (Note 5) VGS > 3V (Note 5) VGS > 3V (Note 5) VGS < 1V (Note 5) VGS < 1V (Note 5) VGS < 1V (Note 5) VGS > 3V (Note 5) VGS < 1V (Note 5) ∆VBDIV = ±100mV, RPULLUP = 51k ∆VDCDIV = ±100mV, RPULLUP = 51k
The ● denotes specifications which apply over the full operating temperature range. Note 1: The logic inputs are high impedance CMOS gates with ESD protection diodes to ground and therefore should not be forced below ground. These inputs can however be driven above the VCCP or VCC supply rails as there are no clamping diodes connected between the input pins and the supply rails. This facilitates operation in mixed 5V/3V systems. Note 2: The Selected Operating Mode Truth Table, which defines the operating conditions and logical states associated with each “normal” operating mode, should be used in conjunction with the Electrical
TRUTH TABLE SELECTED MODES
MIN
MAX
UNITS µs µs µs µs µs µs µs µs kHz µs µs
Characteristics table to establish test conditions. Actual production test conditions may be more stringent. Note 3: The following inputs are high impedance CMOS inputs: 3DM and DCIN/BAT and have no internal pull-up current. Note 4: The following inputs have built-in 2µA pull-up current sources (passed through series diodes): BATSEL, BATDIS and CHGSEL. Note 5: Gate turn-on and turn-off times are measured with no inrush current limiting, i. e., VSENSE = 0V, using Si4936DY MOSFETs in the typical application circuit.
(Selected Operating Modes) LOGIC INPUTS
SWITCH STATUS SW SW SW C/D E/F G Off Off Off Off Off On
SW H Off Off
CHGMON Hi-Z BAT1
Off
Off
Off
Hi-Z
BAT2
H
H
Off
Off
On
BAT2
BAT2
H
H
Off On Off
Off Off Off
Off Off Off
Hi-Z Hi-Z Hi-Z
BAT1 BAT2 BAT1
H H L
L L L
Off Off
Off Off
Off Off
Hi-Z Hi-Z
BAT1 BAT2
L L
L L
3DM* Off Off Off
Off Off
Hi-Z Hi-Z
BAT1 BAT1
L L
H H
SW NO. MODE 3DM DCIN/BAT BATSEL BATDIS CHGSEL A/B 1 DC Operation H H H L H On 2 DC Operation and H H H H H On BAT1 Charging 3 DC Operation and H H L L L On Off BAT2 Disconnected 4 DC Operation and H H L H L On Off BAT2 Charging 5 BAT1 Operation H L H H H Off On 6 BAT2 Operation H L L H H Off Off 7 BAT1 Low and H L H L H Off Off Disconnected 8 Backup Operation H L H L H Off Off 9 No Power L L L L L Off Off (No Backup) 10 DC Reconnected L L H L H 3DM* 3DM* 11 DC Connected H H H L H On Off and Reset * 3DM = Three Diode Mode. When this mode is invoked, only the first MOSFET switch in each back-to-back switch pair, i. e., SW A, SW C and SW E is turned on. Current may still pass through the inherent body diode of the idled switches, i.e., SW B, SW D and SW F to help restart
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TYP 30 30 30 3 3 3 300 5 30 5 5
OUTPUTS VBAT LOBAT BAT1 H BAT1 H
DCINGOOD H H
the system after abnormal operating conditions have been encountered. See the Timing Diagram and Applications Information sections for further details.
LTC1479 U W
TYPICAL PERFORMANCE CHARACTERISTICS MODE 1, DCDIV = 1.5V NO OTHER POWER TJ = 25°C
250 200 150 100
BAT2 Supply Current 350
MODE 5 NO OTHER POWER TJ = 25°C
300
BAT1 SUPPLY CURRENT (µA)
300
250 200 150 100
20 30 15 25 10 DCIN SUPPLY VOLTAGE (V)
0
35
5
20 30 15 25 10 BAT1 SUPPLY VOLTAGE (V)
VBKUP Supply Current 70
150 100
35
0 0
VGG SUPPLY VOLTAGE (V)
42
50 40 30 20
35
1479 G03
MODE 1 VDCIN = 24V
40 38 36 34
30 50 100 25 75 – 50 – 25 0 JUNCTION TEMPERATURE (°C)
0 0
5
20 30 15 25 VBKUP SUPPLY VOLTAGE (V) 10
35
125
1479 G05
1479 G04
VCC Supply Voltage 3.9
20 30 15 25 10 BAT2 SUPPLY VOLTAGE (V)
32
10
4.0
5
VGG Supply Voltage 44
MODE 8 NO OTHER POWER TJ = 25°C
60
200
1479 G02
1479 G01
VCCP Supply Voltage 6.5
MODE 1 VDCIN = 24V
6.0
VCCP SUPPLY VOLTAGE (V)
5
VBKUP SUPPLY CURRENT (µA)
0
250
50
0
0
MODE 6 NO OTHER POWER TJ = 25°C
300
50
50
VCC SUPPLY VOLTAGE (V)
DCIN SUPPLY CURRENT (µA)
BAT1 Supply Current 350
BAT2 SUPPLY CURRENT (µA)
DCIN Supply Current 350
3.8 3.7 3.6 3.5 3.4
MODE 1 VDCIN = 24V
5.5 5.0 4.5 4.0 3.5
3.3 50 100 25 75 – 50 – 25 0 JUNCTION TEMPERATURE (°C)
125
1479 G06
3.0 50 100 25 75 – 50 – 25 0 JUNCTION TEMPERATURE (°C)
125
1479 G07
5
LTC1479
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PIN FUNCTIONS External Power Supply Pins DCIN (Pin 1): Supply Input. A 330Ω resistor should be put in series with this pin and the external DC power source. A 0.1µF bypass capacitor should be connected to this pin as close as possible. DCDIV (Pin 2): Supply Divider Input. This is a high impedance comparator input with a 1.215V threshold (rising edge) and approximately – 35mV hysteresis. BAT1, BAT2 (Pins 35, 34): Supply Input. These two pins are the inputs from the two batteries. A 1µF bypass capacitor should be connected to each pin as close as possible if there is no larger battery supply capacitor within 2". VBAT (Pin 32): Battery Voltage Sense. This pin connects the top of the battery resistor ladder to either BAT1 or BAT2. BDIV (Pin 33): Battery Divider Input. A high impedance comparator input with a 1.215V threshold (falling edge) and approximately 35mV hysteresis. VBKUP (Pin 36): Supply Input. This input supplies power to the LTC1479 when in the backup mode of operation. A 1µF bypass capacitor should be connected to the VBKUP pin as close as possible if there is no larger backup supply capacitor within 2".
micropower gate drive circuitry. Do not load this pin with any external circuitry. Bypass this pin with a 1µF/50V capacitor. SW (Pin 18): Output. This pin drives the “bottom” of the VGG switching regulator inductor which is connected between this pin and the V + pin. GND (Pin 19): Ground. The VGG and V + bypass capacitors should be returned to this ground which is connected directly to the source of the N-channel switch in the VGG regulator. Input Power Switches GA, GB (Pins 4, 6): DCIN Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switches in series with the DCIN input. SAB (Pin 5): Source Return. The SAB pin is connected to the sources of SW A and SW B. A small pull-down current source returns this node to 0V when the switches are turned off. GC, GD (Pins 7, 9): BAT1 Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switches in series with the BAT1 input.
Internal Power Supply Pins
SCD (Pin 8): Source Return. The SCD pin is connected to the sources of SW C and SW D. A small pull-down current source returns this node to 0V when the switches are turned off.
VCCP (Pin 20): Power Supply Output. Bypass this output with at least a 0.1µF capacitor. The VCCP power supply is used primarily to power internal logic circuitry.
GE, GF (Pins 10, 12): BAT2 Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switches in series with the BAT2 input.
VCC (Pin 15): Power Supply Output. This is a nominal 3.60V output. Bypass this regulator output with a 2.2µF tantalum capacitor. This capacitor is required for stability.
SEF (Pin 11): Source Return. The SEF pin is connected to the sources of SW E and SW F. A small pull-down current source returns this node to 0V potential when the switches are turned off.
V + (Pin 17): Supply. The V + pin is connected via three internal diodes to the DCIN, BAT1 and BAT2 pins and powers the top of the VGG switching regulator inductor. Bypass this pin with a 1µF/35V capacitor. VGG (Pin 16): Gate Supply. This high voltage (36.5V) switching regulator is intended only for driving the internal
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SENSE + (Pin 13): Inrush Current Input. This pin should be connected directly to the “top” (switch side) of the low valued resistor in series with the three input power selector switch pairs, SW A/B, SW C/D and SW E/F, for detecting and controlling the inrush current into and out of the power supply sources and the output capacitor.
LTC1479
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PIN FUNCTIONS SENSE – (Pin 14): Inrush Current Input. This pin should be connected directly to the “bottom” (output side) of the low valued resistor in series with the three input power selector switch pairs, SW A/B, SW C/D and SW E/F, for detecting and controlling the inrush current into and out of the power supply sources and the output capacitor. Battery Charging Switches GG, GH (Pins 29, 27): Charger Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switch pairs, SW G and SW H, between the charger output and the two batteries. SG, SH (Pin 28, 26): Source Returns. These two pins are connected to the sources of SW G and SW H respectively. A small pull-down current source returns these nodes to 0V when the switches are turned off. CHGMON (Pin 31): Battery Selector Output. This pin is the output of an internal switch which is connected to BAT1 and BAT2 and connects the positive terminal of the selected battery to the voltage feedback resistors in the charger circuit. Microprocessor Interface DCINGOOD (Pin 25): Comparator Output. This open-drain output has an internal 2µA pull-up current source connected through a diode to the VCCP power supply. An external pull-up resistor can be added if more pull-up current is required. This output is active high when the DC supply rises above the programmed voltage.
LOBAT (Pin 3): Comparator Output. This open-drain output does not have an internal pull-up current source and is active low when the selected battery voltage drops below the programmed voltage. DCIN/BAT (Pin 24): Selector Input. This high impedance logic input allows the µP to make the ultimate decision on the connection of the DC power source, based upon the DCINGOOD pin information. In some minimized systems, the DCIN/BAT pin may be connected directly to the DCINGOOD pin. BATDIS (Pin 23): Battery Disconnect Input. This highimpedance logic input has a built-in 2µA pull-up current source and allows the µP to disconnect the battery from the system. 3DM (Pin 22): Three Diode Mode Input. This high impedance logic input has no built-in pull-up current source. Connect a 100k resistor from this pin to ground to ensure three diode mode operation from a “cold start.” CHGSEL (Pin 21): Battery Charger Selector Input. This high impedance logic input has a built-in 2µA pull-up current source and allows the µP to determine which battery is being charged by connecting the selected battery to the charger output via one of the switch pairs, SW G or SW H. (The charger voltage feedback ladder is simultaneously switched to the selected battery.) BATSEL (Pin 30): Battery Selector Input. This high impedance logic input has a built-in 2µA pull-up current source and allows the µP to select which battery is connected to the system and the battery monitor comparator input. Battery 1 is selected with a logic high on this input and battery 2 is selected with a logic low.
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LTC1479
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BLOCK DIAGRAM DCIN
GA
SAB
GB
GC
SCD
GD
GE
SEF
GF
VSENSE +
DCIN MONITOR
DCDIV
SW A/B GATE DRIVERS BAT1 BAT2
SW C/D GATE DRIVERS
BAT2 INRUSH SENSE
SW E/F GATE DRIVERS
BAT1 INRUSH SENSE
DCIN
DCIN INRUSH SENSE
V+
VCC
VSENSE –
VCC REGULATOR & BIAS GENERATOR
VCCP
VCCP
VCCP 2µA
2µA
2µA
VCCP
VGG
SWITCH CONTROL LOGIC
SW
3DM BATDIS DCIN/BAT DCINGOOD
VGG SWITCHING REGULATOR
BAT1 BAT2 DCIN
VCCP
VBKUP 2µA LOBAT BATTERY MONITOR
VCCP BAT2
SW G GATE DRIVER
GND
SW H GATE DRIVER
BAT1
BATSEL
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VBAT
CHGSEL
CHGMON
BDIV
SG
GG
SH
GH
1479 BD
LTC1479
WU W TI I G DIAGRA S DC and Battery Operation Timing MODE 1 DC OPERATION BAT1 DISCONNECTED
MODE 2 DC OPERATION BAT1 CHARGING
MODE 3 DC OPERATION BAT2 DISCONNECTED
MODE 4 DC OPERATION BAT2 CHARGING
MODE 5 BAT1 OPERATION
MODE 6 BAT2 OPERATION
25V DCIN 0V 25V (16V)
OUTPUT
(12V)
0V DCINGOOD DCIN/BAT BATDIS BATSEL CHGSEL
1479 TD01
NOTE: FOR MODES 1 TO 6, 3DM = H, BAT1 = 16V, BAT2 = 12V
Backup and DC Restoration Timing
MODE 7 BAT1 LOW & DISCONNECTED
MODE 8 BACKUP OPERATION
MODE 9 NO POWER (NO BACKUP)
MODE 10 DC RESTORED (THREE DIODE MODE)
MODE 11 DC RECONNECTED (SW A/B ON)
MODE 12 THREE DIODE MODE
25V DCIN 0V (25V) 25V OUTPUT 0V
BAT1 DISCHARGING
(24.3V)
(24.3V)
(VBKUP = 6V) (0V)
LOBAT BATDIS DCIN/BAT 3DM 1479 TD02
NOTE: FOR MODES 7 TO 12, BATSEL = H, BAT1 = 16V AND DISCHARGING, BAT2 = 0V
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LTC1479
U OPERATION The LTC1479 is responsible for low-loss switching at the “front end” of the power management system, where up to two battery packs and a DC power source can be indiscriminately connected and disconnected. Smooth switching between input power sources is accomplished with the help of low-loss N-channel switches driven by special gate drive circuitry which limits the inrush current in and out of the battery packs and the system power supply capacitors. All N-Channel Switching The LTC1479 drives external back-to-back N-channel MOSFET switches to direct power from the three main power sources: the external DC power source, the primary battery and the secondary battery connected to the main supply pins—DCIN, BAT1 and BAT2 respectively. (N-channel MOSFET switches are more cost effective and provide lower voltage drops than their P-channel counterparts.) Gate Drive (VGG) Power Supply The gate drive for the low-loss N-channel switches is supplied by a micropower boost regulator which is regulated at approximately 36.5V. The VGG supply provides sufficient headroom above the maximum 28V operating voltage of the three main power sources to ensure that the MOSFET switches are fully enhanced. The power for this inductor based regulator is taken from three internal diodes as shown in Figure 1. The three
diodes are connected to each of the three main power sources, DCIN, BAT1 and BAT2. The highest voltage potential is directed to the top of the boost regulator inductor to maximize regulator efficiency. C1 provides filtering at the top of the 1mH switched inductor, L1, which is housed in a small surface mount package. A fourth internal diode directs the current from the 1mH inductor to the VGG output capacitor, C2, further reducing the external parts count. In fact, as demonstrated in Figure 1, only three external components are required by the VGG regulator, L1, C1 and C2. Inrush Current Limiting The LTC1479 uses an adaptive inrush current limiting scheme to reduce current flowing in and out of the three main power sources and the DC/DC converter input capacitor during switch-over transitions. The voltage across a single small-valued resistor, RSENSE, is measured to ascertain the instantaneous current flowing through the three main switch pairs, SW A/B, SW C/D, and SW E/F during the transitions. Figure 2 is a block diagram showing only the DCIN switch pair, SW A/B. (The gate drive circuits for switch pairs SW C/D and SW E/F are identical). A bidirectional current sensing and limiting circuit determines when the voltage drop across RSENSE reaches plus or minus 200mV. The gate-to-source voltage, VGS, of the appropriate switch is limited during the transition period until the inrush current subsides, generally within a few milliseconds, depending upon the value of the DC/DC converter input capacitor.
DCIN BAT1 BAT2 LTC1479
SW A
V+
TO GATE DRIVERS
(36.5V)
VGG SW
SW B
RSENSE
DCIN
+
L1 1mH
GA LTC1479
+
VGG SWITCHING REGULATOR
C2 1µF 50V
+
6V
SAB
GB
VSENSE +
VSENSE –
6V ±200mV THRESHOLD
C1 1µF 35V
VGG
SW A/B GATE DRIVERS
BIDIRECTIONAL INRUSH CURRENT SENSING AND LIMITING
GND 1479 F01
Figure 1. VGG Switching Regulator
10
1479 F02
Figure 2. SW A/B Inrush Current Limiting
OUTPUT TO DC/DC CONVERTER COUT
LTC1479
U OPERATION This scheme allows capacitors and MOSFET switches of differing sizes and current ratings to be used in the same system without circuit modifications. After the transition period has passed, the VGS of both MOSFETs in the selected switch pair rises to approximately 6V. The gate drive is set at 6V to provide ample overdrive for logic level MOSFET switches without exceeding their maximum VGS rating. Internal Power Supplies Two internal supplies provide power for the control logic and power source monitoring functions. The VCCP logic supply is approximately 5V and provides power for the majority of the internal logic circuitry. The VCC supply is approximately 3.60V and provides power for the VGG switching regulator control circuitry and the gate drivers. The VCC supply has an undervoltage lockout circuit which minimizes power consumption in the event of a total loss of system power; i.e., when all available power sources fall below approximately 4.5V. DCIN Voltage Monitoring The DCIN input is continuously monitored via a two resistor ladder connected between the DCIN pin and the DCDIV input. The input threshold is 1.215V (rising edge) with approximately – 35mV hysteresis. The use of a definitive voltage threshold ensures that the DC supply is not only connected but “healthy” before being attached to the DC/DC converter input.
Battery Charging Management Functions The LTC1479 directly interfaces with LT1510/LT1511 battery charger circuits. Two gate drive circuits control the two back-to-back N-channel switch pairs, SW G and SW H, under logic (CHGSEL) control to connect the output of the charger to the selected battery pack. Breakbefore-make action ensures that current does not pass from one battery pack to the other during switch-over of the charger output. The CHGSEL input also simultaneously switches the positive terminal of the selected battery pack to the top of the voltage feedback resistor ladder in the charger system through the CHGMON pin. Backup Supply Interface Power for the LTC1479 is obtained from the backup supply when power is unavailable from the three main sources of power. Interface to Companion Microprocessor A companion µP must be used in conjunction with the LTC1479 to provide overall control of the power management system. The LTC1479 communicates with the µP by means of five logic inputs and two logic outputs as described in Table 1. Table 1. LTC1479 µP Interface Inputs and Outputs INPUT
ACTION
DCIN/BAT
Logic High Required to Connect a Good DC Supply
BATDIS
Logic Low Disconnects the Battery from the System
BATSEL
Selects Which Battery is Connected to the System (Logic High Selects BAT1; Logic Low Selects BAT2)
Battery Voltage Monitoring
CHGSEL
The LTC1479 has the ability to independently monitor both battery packs. (Because of this, one battery pack may be discharged as the other is being charged.)
Selects Which Battery is Charged and Monitored (Logic High Selects BAT1; Logic Low Selects BAT2)
3DM
Forces the Main Three Power Path Switches Into “3-Diode Mode.” See Applications Information Section
OUTPUT
ACTION
A low-battery detector signals when the selected battery pack has dropped to the level where a shutdown sequence should be initiated or the other battery pack engaged.
DCINGOOD
Logic High When a Good DC Supply is Present
LOBAT
Logic Low When Selected Battery Voltage is Low
11
LTC1479
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APPLICATIONS INFORMATION POWER PATH SWITCHING CONCEPTS Power Source Selection The LTC1479 drives low-loss switches to direct power in the main power path of a dual rechargeable battery system — the type found in most notebook computers and other portable equipment. Figure 3 is a conceptual block diagram which illustrates the main features of an LTC1479 dual battery power management system, starting with the three main power sources and ending at the system DC/DC regulator. Switches SW A/B, SW C/D and SW E/F direct power from either the AC adapter (DCIN) or one of the two battery packs (BAT1 and BAT2) to the input of the DC/DC switching regulator. Switches SW G and SW H connect the desired battery pack to the battery charger.
Note: The capacitor manufacturer should be consulted for specific inrush current specifications and limitations and some experimentation may be required to ensure compliance with these limitations under all possible operating conditions. Back-to-Back Switch Topology The simple SPST switches shown in Figure 3 actually consist of two back-to-back N-channel switches. These low-loss, N-channel switch pairs are housed in 8-pin SO and SSOP packaging and are available from a number of manufacturers. The back-to-back topology eliminates the problems associated with the inherent body diodes in power MOSFET switches and allows each switch pair to block current flow in either direction when the two switches are turned off.
Each of the five switches is intelligently controlled by the LTC1479 which interfaces directly with a power management system µP.
The back-to-back topology also allows for independent control of each half of the switch pair which facilitates bidirectional inrush current limiting and the so called “3diode” mode described in the following section.
Using Tantalum Capacitors
The “3-Diode” Mode
The inrush and “outrush” current of the system DC/DC regulator input capacitor is limited by the LTC1479. i.e., the current flowing both in and out of the capacitor during transitions from one input power source to another is limited. In many applications, this inrush current limiting makes it feasible to use lower cost/size tantalum surface mount capacitors in place of more expensive/larger aluminum electrolytics at the input of the DC/DC converter.
Under normal operating conditions, both halves of each switch pair are turned on and off simultaneously. For example, when the input power source is switched from a good DC input (AC adapter) to a good battery pack, BAT1, both gates of switch pair SW A/B are turned off and both gates of switch pair SW C/D are turned on. The back-toback body diodes in switch pair, SW A/B, block current flow in or out of the DC input connector.
SW A/B DCIN SW C/D
RSENSE 12V
BAT1
+
SW E/F CIN
BAT2 SW G
SW H
HIGH EFFICIENCY DC/DC SWITCHING REGULATOR
5V
3.3V BATTERY CHARGER LTC1479 PowerPath CONTROLLER
Figure 3. LTC1479 PowerPath Conceptual Diagram
12
POWER MANAGEMENT µP
1479 F03
LTC1479
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APPLICATIONS INFORMATION In the “3-diode” mode, only the first half of each power path switch pair, i.e., SW A, SW C and SW E, is turned on; and the second half, i.e., SW B, SW D and SW F, is turned off. These three switch pairs now act simply as three diodes connected to the three main input power sources as illustrated in Figure 4. The power ‘diode’ with the highest input voltage passes current through to the input of the DC/DC converter to ensure that the power management µP is powered at start-up or under abnormal operating conditions. (An undervoltage lockout circuit defeats this mode when the V + pin drops below approximately 4.5V). “Cold Start” Initial Condition The LTC1479 is designed to start in the “3- diode” mode when all five logic inputs are low— when no power is available (including the backup system). A 100k resistor from the 3DM input to ground ensures that this input is low during a “cold start.” This will cause the main PowerPath switches to pass the highest voltage available to the input of the DC/DC converter. Normal operation will then resume after a good power source is identified. Recovery from Uncertain Power Conditions The “3-diode” mode can also be asserted (by applying an active low to the 3DM input) when abnormal conditions exist in the system, i.e., when all power sources are deemed not “good” or are depleted, or the management system µP is being reset or not functioning properly. (See
the Power Management µP Interface section for additional information on when to invoke “3-diode” mode.) COMPONENT SELECTION N-Channel Switches The LTC1479 adaptive inrush limiting circuitry permits the use of a wide range of logic-level N-channel MOSFET switches. A number of dual low RDS(ON) N-channel switches in 8-lead surface mount packages are available that are well suited for LTC1479 applications. The maximum allowable drain source voltage, VDS(MAX), of the three main switch pairs, SW A/B, SW C/D and SW E/F, must be high enough to withstand the maximum DC supply voltage. If the DC supply is in the 20V to 28V range, use 30V MOSFET switches. If the DC supply is in the 10V to 18V range, and is well regulated, then use 20V MOSFET switches. As a general rule, select the switch with the lowest RDS(ON) at the maximum allowable VDS. This will minimize the heat dissipated in the switches while increasing the overall system efficiency. Higher switch resistances can be tolerated in some systems with lower current requirements, but care should be taken to ensure that the power dissipated in the switches is never allowed to rise above the manufacturer’s recommended levels. The maximum allowable drain-source voltage, VDS(MAX), of the two charger switch pairs, SW G and SW H, need only
SW B SW A DCIN SW D ON
OFF
SW C
RSENSE 12V
BAT1
+
SW F ON
OFF
CIN
SW E
BAT2 ON
OFF
HIGH EFFICIENCY DC/DC SWITCHING REGULATOR
5V
3.3V
LTC1479 PowerPath CONTROLLER
POWER MANAGEMENT µP
1479 F04
Figure 4. LTC1479 PowerPath Switches in “3-Diode” Mode
13
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APPLICATIONS INFORMATION be high enough to withstand the maximum battery or charger output voltage. In most cases, this will allow the use of 20V MOSFET switches in the charger path, while 30V switches are used in the main power path.
DC SUPPLY
TO SW A/B LTC1479 DCIN
DCINGOOD
+
1.215V
RDC2 1% DCDIV
Inrush Current Sense Resistor, RSENSE A small valued sense resistor (current shunt) is used by the three main switch pair drivers to measure and limit the inrush current flowing through the conducting switch pair.
It should be noted that the inrush limiting circuit is not intended to provide short-circuit protection ; but rather, is designed to limit the large peak currents which flow into or out of the large power supply capacitors and the battery packs during power supply switch-over transitions. The inrush current limit should be set at approximately 2× or 3× the maximum required DC/DC input current. For example, if the maximum current required by the DC/DC converter is 2A, an inrush current limit of 6A is set by selecting a 0.033Ω sense resistor, RSENSE, using the following formula: RSENSE = (200mV)/IINRUSH Note that the voltage drop across the resistor in this example is only 66mV under normal operating conditions. Therefore, the power dissipated in the resistor is extremely small (132mW), and a small 1/4W surface mount resistor can be used in this application. A number of small valued, surface mount resistors are available that have been specifically designed for high efficiency current sensing applications. DC Input Monitor Resistor Divider The DCDIV input continuously monitors the DC power supply voltage via a two resistor divider network, RDC1 and RDC2, as shown in Figure 5. The threshold voltage of the DC good comparator is 1.215V when the power supply input voltage is rising. Approximately – 35mV of hysteresis is provided to ensure clean switching of the comparator when the DC supply voltage is falling. To minimize errors due to the input bias current of the DC good comparator, set RDC1 = 12.1k so that approximately 100µA flows through the resistor divider when the desired
14
–
RDC1 12.1k 1%
1479 F05
Figure 5. DC Monitor Resistor Divider BATSEL BAT1 SWITCH CONTROL LOGIC
BAT2 VBAT
RB2 1%
1.215V
BDIV RB1 121k 1%
LOBAT
+ –
LTC1479 1479 F06
Figure 6. Battery Monitor Resistor Divider
threshold is reached. RDC2 is then selected according to the following formula: RDC2 = 12.1k
)
)
VGOOD –1 1.215V
Battery Monitor Resistor Divider A switch controlled by the BATSEL input connects one of the two batteries to the VBAT pin and therefore to the top of the battery resistor divider as shown in Figure 6. The threshold voltage of the low-battery comparator is 1.215V when the battery voltage is falling. Approximately +35mV of hysteresis is provided to ensure clean switching of the comparator when the battery voltage rises again. To minimize errors due to the input bias current of the low battery comparator, assume RB1 = 121k so that approximately 10µA flows through the resistor divider when the threshold is reached. RB2 is selected according to the following formula:
LTC1479
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APPLICATIONS INFORMATION
)
)
The VCC supply is approximately 3.60V and provides power for the VGG switching regulator control circuitry and the gate drivers. Bypass this output with a 2.2µF tantalum capacitor. This capacitor is required for stability of the VCC regulator output.
V RB2 = 121k LOBAT – 1 1.215V
VGG Regulator Inductor and Capacitors The VGG regulator provides a power supply voltage significantly higher than any of the three main power source voltages to allow the control of N-channel MOSFET switches. This 36.5V micropower, step-up voltage regulator is powered by the highest potential available from the three main power sources for maximum regulator efficiency. Because the three input supply diodes and regulator output diode are built into the LTC1479, only three external components are required by the VGG regulator: L1, C1 and C2 as shown in Figure 7. L1 is a small, low current 1mH surface mount inductor. C1 provides filtering at the top of the 1mH switched inductor and should be 1µF to filter switching transients. The VGG output capacitor, C2, provides storage and filtering for the VGG output and should be 1µF and rated for 50V operation. C1 and C2 can be either tantalum or ceramic capacitors. VCC and VCCP Regulator Capacitors The VCCP logic supply is approximately 5V and provides power for the majority of the internal logic circuitry. Bypass this output with a 0.1µF capacitor. DCIN BAT1 BAT2 LTC1479 V+
TO GATE DRIVERS
(36.5V)
VGG SW
VGG SWITCHING REGULATOR
L1* 1mH
+
C2 1µF 50V
+
C1 1µF 35V
SYSTEM LEVEL CONSIDERATIONS The Complete Power Management System The LTC1479 is the “heart” of a complete power management system and is responsible for the main power path and charger switching. A companion power management µP provides overall control of the power management system in concert with the LTC1479 and the auxiliary power management systems. A typical dual Li-Ion battery power management system is illustrated in Figure 8. If “good” power is available at the DCIN input (from the AC adapter), switch pair SW A/B are turned on—providing a low-loss path for current flow to the input of the LTC1538-AUX DC/DC converter. Switch pairs, SW C/D and SW E/F are turned off to block current from flowing back into the two battery packs from the DC input. In this case, an LT1510 constant-voltage/constant-current (CC/CV) battery charger circuit is used to alternately charge the two Li-Ion battery packs. The µP “decides” which battery is in need of recharging by either querying the “smart” battery directly or by more indirect means. After the determination is made, either switch pair, SW G or SW H, is turned on to pass charger output current to one of the batteries. Simultaneously, the selected battery voltage is returned to the voltage feedback input of the LT1510 CV/CC battery charger via the CHGMON output of the LTC1479. After the first battery has been charged, it is disconnected from the charger circuit and the second battery is connected through the other switch pair and the second battery charged. Backup power is provided by the LT1304 circuit which ensures that the DC/DC input voltage does not drop below 6V.
GND 1479 F07
*COILCRAFT 1812LS-105 XKBC (708) 639-6400 OR EQUIVALENT
Figure 7. VGG Step-Up Switch Regulator
Backup System Interface The LTC1479 is designed to work in concert with related power management products including the LT1304 mi-
15
LTC1479
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APPLICATIONS INFORMATION SW A
DCIN
RSENSE 0.033Ω
SW B
12V AUX SW C
LTC1538-AUX TRIPLE, HIGH EFFICIENCY, SWITCHING REGULATOR
SW D SW E
RDC2
3.3V
SW F
0.1µF
330Ω
Li-ION BATTERY PACK #1
5V
BACKUP NiCD GA SAB GB
DCIN
GE SEF GF SENSE + SENSE –
GC SCD GD
DCDIV BACKUP REGULATOR
VBKUP
RDC1
BAT1 BAT2 Li-ION BATTERY PACK #2
LTC1479
2
VBAT RB2 BDIV
5
POWER MANAGEMENT µP
RB1 CHGMON VCC 2.2µF 16V
V+
VCCP
+
SW VGG
GG SG
GH SH DCIN
1mH*
+ 0.1µF
1µF 50V
+
1µF 50V
+ SW H
LT1510 Li-ION BATTERY CHARGER
SW G 1479 F08
*COILCRAFT 1812LS-105 XKBC (708) 639-1469
Figure 8. Simplified Dual Li-Ion Battery Power Management System
FROM PowerPath CONTROLLER 5VCC FROM DC/DC
(BOLD LINES INDICATE HIGH CURRENT PATHS) ROHM DTA144E
R1 10k
+
NiCD CELL
R4 390k 1% 4
Q1 2N7002
R5 100k 1%
SW 2
D2 BAS16LT1
1
LBO
FB LT1304
ILIM C2 0.1µF
SHDN
LBI 6 R3 22k
GND
VIN
8
Charger System Interface The LTC1479 is designed to work directly with constantvoltage (CV), constant-current (CC) battery chargers such as the LT1510 and LT1511.
7 5VCC FROM DC/DC
3
5 C3 0.1µF
LT1510 Battery Charger Interface 1479 F09
Figure 9. LT1304 Micropower Backup Converter Circuit
16
cropower DC/DC converter. As shown in Figure 9, the LT1304 monitors the input supply voltage and activates when it drops below 6V. Power for the DCIN and battery monitors and the logic supply in the LTC1479 is then obtained from the output of the LT1304 step-up regulator.
C1 0.1µF
BACKUP
R2 470k
D1 MBR0530
L1* 10µH
TO INPUT OF DC/DC CONVERTER
As illustrated in Figure 10, the LT1510 CV/CC battery charger, takes power from the DC adapter input through Schottky diode D1. The output of the charger is directed to
LTC1479
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the charging battery through one of the N-channel switch pairs, SW G or SW H. The charging battery voltage is simultaneously connected through the CHGMON switch in the LTC1479 to the top of the charger voltage resistor divider, R4 and R5, for constant voltage charging. (See the LT1510 data sheet for further detail.)
The LT1511, 3A CC/CV battery charger with input current limiting, is connected in a slightly different manner than the LT1510 as illustrated in Figure 11.
CHGMON
POWER MANAGEMENT µP
LTC1479
D1 MBRS140T
0.1µF TO SW C/D
+ BAT1 4 Li-ION BATTERY PACK
BAT2 4 Li-ION BATTERY PACK
TO SW A/B
TO SW E/F
+C
BAT1
RPROG 11k 1%
47µF
–
SW G Si9926DY
+ –
C6 10µF CERAMIC
D2 MBRS140T
VCC SW C3 0.22µF
PROG VC BOOST
R1 100k 1%
R3 1k
R2 300Ω C1 1µF
C2 0.1µF
L1* 33µH
D3 1N4148
LT1510
R4 649k 0.25%
SENSE
Q1 2N7002
+ CBAT2 47µF
DC INPUT (FROM AC ADAPTOR)
330Ω
BAT2 GG SG GH SH DCIN
BAT1
GND
OVP BAT
R5 115k 0.25%
SW H Si9926DY (CHARGER OUTPUT)
+
CCHG 22µF TANT
CURRENT CONTROL FROM POWER MANAGEMENT µP
*COILTRONICS CTX33-2
1479 F10
Figure 10. Interfacing to the LT1510 Constant-Voltage/Constant-Current Battery Charger
CHGMON
POWER MANAGEMENT µP
LTC1479 BAT1
RS4 0.05Ω
330Ω
BAT2 GG SG GH SH
C4 10µF CERAMIC
0.1µF
+
TO SW A/B
CBAT1 47µF
RPROG 4.93k 1% C1 1µF
SW G Si9926DY
–
R1 500Ω
+
R2 1k C2 0.33µF
COMP1 BOOST C3 200pF
LT1511 SPIN GND BAT
CBAT2 47µF
SW H Si9926DY
Q1 2N7002
–
RS2 200Ω 1% (CHARGER OUTPUT)
+ CURRENT CONTROL FROM POWER MANAGEMENT µP
R3 500Ω
CLN VCC CLP UV PROG SW VC
+ BAT2 4 Li-ION BATTERY PACK
C12 1µF
C5 10µF
+ +
DC INPUT (FROM AC ADAPTOR)
DCIN
TO SW C/D TO SW E/F
BAT1 4 Li-ION BATTERY PACK
D1 MBRS340T
OVP SENSE
RS1 0.033Ω
RS3 200Ω 1%
R4 5k R5 6.8k
D2 MBRS340T C6 0.47µF L1 20µH D3 MBR0540T
C7 50pF
R6 649k 0.25% R7 115k 0.25% 1479 F11
CCHG 22µF TANT
Figure 11. Interfacing to the LT1511 Constant-Voltage/Constant-Current Battery Charger with Input Current Limiting
17
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APPLICATIONS INFORMATION The LT1511 has a third control loop that regulates the current drawn from the AC adapter. Therefore, the DC input to the LTC1479 and the input to the host system through SW A/B, is obtained from the “output” of the LT1511 adapter sense resistor, RS4, and not directly from the DC input connector as with the LT1510. This allows simultaneous operation of the host system while charging a battery without overloading the AC adapter. Charging current is reduced to keep the adapter current within specified levels.
capacitance to ground on the CHGMON output to less than 100pF. If more capacitance is required, it may become necessary to “mask” the LOBAT output when the charge monitor is switched between batteries. (Internal resistance between the BAT1 and BAT2 inputs and the charge monitor switch may create a transient voltage drop at the VBAT output during transitions which could be falsely interpreted by the µP as a low battery condition.)
However, as with the LT1510 , the output of the LT1511 is directed to the charging battery through either SW G or SW H, and the charging battery voltage is connected to the top of the voltage resistor divider, R6 and R7, for constant voltage charging. (See the LT1511 data sheet for further detail on battery charging techniques and applications hints.)
Interfacing to the LTC1479
LT1620/LTC1435 Battery Charger Interface The LTC1479 also interfaces with the LT1620/LTC1435 synchronous high efficiency low dropout battery charger. The circuit shown in Figure 12 is a constant-current/ constant-voltage battery charger specifically designed for lithium-ion applications having thermal, output current, or input voltage headroom constraints which preclude the use of other high performance chargers such as the LT1510 or LT1511. This circuit can charge batteries at up to 4A. The precision current sensing of the LT1620 combined with the high efficiency and low dropout characteristics of the LTC1435 provide a battery charger with over 96% efficiency requiring only 0.5V input-to-output differential at 3A charging current. Charge current programming is achieved by applying a 0µA to 100µA current from the LT1620 PROG pin to ground, which can be derived from a resistor or DAC output controlled by the power management µP. (See the LT1620 data sheet for further details on this circuit.) Capacitive Loading on the CHGMON Output In most applications, there is virtually no capacitive loading on the CHGMON output—just a simple resistor divider. Care should be taken to restrict the amount of
18
THE POWER MANAGEMENT MICROPROCESSOR
The LTC1479 can be thought as a “real world” interface to the power management µP. It takes logic level commands directly from the µP, and makes changes at high current and high voltage levels in the power path. Further, it provides information directly to the µP on the status of the AC adapter, the batteries and the charging system. The LTC1479 logic inputs are TTL level compatible and therefore interface directly with standard power management µPs. Further, because of the direct interface via the five logic inputs and the two logic outputs, there is virtually no latency (i.e. time delay) between the µP and the LTC1479. In this way, time critical decisions can be made by the µP without the inherent delays associated with bus protocols, etc. These delays are acceptable in certain portions of the power management system, but it is vital that the power path switching control be made through a direct connection to the power management µP. The remainder of the power management system can be easily interfaced to the µP through a serial interface. Selecting a Power Management Microprocessor The power management µP provides intelligence for the entire power system, is programmed to accommodate the custom requirements of each individual system and allow performance updates without resorting to costly hardware changes. The power management µP must meet the requirements of the total power management system, including the LTC1479 controller, the batteries (and interface), the backup system, the charging system and the host processor. A number of inexpensive processors are available which can easily fulfill these requirements.
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APPLICATIONS INFORMATION CHGMON
POWER MANAGEMENT µP
LTC1479
DC INPUT (FROM AC ADAPTER)
330Ω
BAT2 GG SG GH SH DCIN
BAT1
0.1µF TO SW C/D TO SW E/F
TO W A/B
+ +
BAT1 4 Li-ION BATTERY PACK
SW G Si9926DY
–
R2 76.8k 0.1%
+ BAT2 4 Li-ION BATTERY PACK
+
CBAT2 10µF
SW H Si9926DY
–
+
C11 56pF
SHDN
R5 1.5M
C3 0.1µF
C2 100pF
1
COSC TG 2 RUN/SS BOOST 3 SW ITH LTC1435 4 VIN SFB 5 INTV SGND CC 6 VOSENSE BG C9, 100pF 7 SENSE – PGND C10 8 VCC SENSE + 100pF
C4 0.033µF
R5, 1k
1 2
SENSE
AVG
8
7 PROG LT1620 3 6 GND VCC 4 5 NIN PIN
IPROG
R1 1M 0.1%
C1 100pF
CBAT1 10µF
IOUT
16 15
L1 27µH
14 13
Q1 Si4412DY
C13 D2* CMDSH-3 0.33µF
12
+
D1* CMDSH-3
11
R4 0.025Ω C16 22µF 35V
Q2 Si4412DY
10 9 C14 4.7µF
C6 0.1µF C7 0.33µF
C5 0.01µF
C12 0.1µF
C15 22µF 35V ×2
C8 0.1µF
+
R3 10k 1% 1479 F12
*CENTRAL SEMICONDUCTOR CO. (516) 435-1110
Figure 12. Interfacing to an LT1620/LTC1435 High Efficiency Constant-Voltage/Constant-Current Battery Charger
19
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APPLICATIONS INFORMATION Interfacing to the Battery Pack The LTC1479 is designed to work with virtually any battery pack chemistry or cell count, as long as the battery pack operating voltage range is somewhere between 6V and 28V. This permits great flexibility in system design. The low-battery threshold is adjustable and can be set anywhere between 6V and 28V. Conventional Battery Packs Conventional battery packs do not include a “smart” battery interface between the battery pack and the host system. Thus, these battery packs generally have only three terminals to connect the battery and a temperature sensor (thermistor) to the host system. The NTC thermistor typically has a nominal resistance of 10k at room temperature and is used to monitor the battery pack temperature. LOBAT and DCINGOOD Blanking/Filtering It is good practice to include some delay in accepting low battery and DCIN good information during transitional periods, e.g., when switching the charger from one battery
20
to another or when switching from batteries to DC power. This technique will eliminate false triggering at the associated µP I/O. (Remember that the “3-diode” mode may be used during periods of uncertainty to eliminate the need for “instantaneous” DCIN and battery status information.) Smart Battery Packs Smart battery packs, compliant with the Smart Battery System specification, have a five-terminal connector. Two of the terminals are the minus and plus connections to the battery. A third terminal is connected to the top of a thermistor in NiCd and NiMH battery packs and to a resistor in Li-Ion battery packs. A fourth and fifth terminal are connected to the Smart Management Bus (SMBus) SMBDATA and SMBCLK lines from an integrated circuit inside the battery pack. Applications Assistance Linear Technology applications engineers have developed a smart battery charger around the LT1511 charger IC. Contact the factory for applications assistance in developing a complete smart battery system with intelligent PowerPath control using the LTC1479.
LTC1479
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TYPICAL APPLICATIONS N Dual NiMH Battery Power Management System (Using an LT1510, 1A Charger) RSENSE 0.033Ω
Si4936DY SW A SW B Si4936DY SW C SW D
330Ω
RDC2 205k 1%
GA SAB GB
DCIN
GC SCD GD
GE SEF GF
SENSE +
D1 L2** 10µH MBR0530
R8 10k NiCD CELL
+
VBKUP
R2 390k 1% Q2 2N7002
LTC1479
R7 470k
BDIV
RB1 121k 1%
VCC GND V + SW C1 0.1µF
VGG
GG SG GH SH BATDIS DCIN/BAT CHGMON LOBAT
+
C3 1µF 50V
+
POWER MANAGEMENT µP
C4 1µF 50V
SMBUS RTH1 RTH2
BAT2 12-CELL NiMH BATTERY PACK
RTH1
C6 10µF CERAMIC
CBAT1 10µF SW G Si9926DY
RPROG 11k 1% Q1 2N7002
+ RTH1
CBAT2 10µF
R4 100k 1%
C11 0.1µF
100k
D2 MBRS140T
+
5
6 R1 22k
VCC
RCM1 100k 1%
BAT1 12-CELL NiMH BATTERY PACK
5VCC FROM DC/DC
(BACKUP)
RCM2 909k 1%
L1* 1mH C2 2.2µF 16V
C10 0.1µF
BATSEL CHGSEL DCINGOOD 3DM
VCCP
+
8 LBO FB LT1304 7 SHDN 1 3 LBI VIN ILIM GND
D5 BAS16LT1
BAT2 VBAT
R3 100k 1%
4 SW
2 BAT1
RB2 909k 1%
C5 0.1µF
SENSE –
DCDIV
RDC1 12.1k 1%
ROHM DTA144E
5VCC FROM DC/DC
Si4936DY SW E SW F
0.1µF
TO INPUT OF DC/DC CONVERTER
(BOLD LINES INDICATE HIGH CURRENT PATHS)
R5 300Ω C8 1µF
8 VCC SW 1 7 PROG 2 6 VC BOOST R6 1k C9 0.1µF 3
+
CDCIN 10µF 35V ALUM
C7 0.22µF
LT1510
GND
SW H Si9926DY
SENSE BAT
4
DC INPUT (FROM AC ADAPTOR)
D3 1N4148
D4 MBRS140T
L3*** 33µH
5 *1812LS-105 XKBC, COILCRAFT **CD43, SUMIDA ***CTX33-2, COILTRONICS
(CHARGER OUTPUT)
+
CCHG 22µF TANT 1479 TA02
21
LTC1479
U
TYPICAL APPLICATIONS N Dual Li-Ion Battery Power Management System
RSENSE 0.033Ω
Si4936DY SW A SW B Si4936DY SW C SW D
330Ω
RDC2 205k 1%
GA SAB GB
DCIN
GC SCD GD
GE SEF GF
SENSE +
R2 390k 1%
Q2 2N7002
LTC1479
RB1 121k 1%
R7 470k
VCC GND V + SW C1 0.1µF
+
C10 0.1µF
BATSEL CHGSEL DCINGOOD 3DM
VCCP VGG
GG SG GH SH BATDIS DCIN/BAT CHGMON LOBAT
+
C3 1µF 50V
+
6 R1 22k
5VCC FROM DC/DC
5 C11 0.1µF
(BACKUP) VCC
100k
L1* 1mH C2 2.2µF 16V
SW
8 LBO FB LT1304 7 SHDN 1 3 LBI VIN ILIM GND
D5 BAS16LT1
BDIV
R3 100k 1%
4 2
BAT2 VBAT
TO INPUT OF DC/DC CONVERTER
C5 0.1µF
SENSE –
BAT1
RB2 909k 1%
D1 L2** 10µH MBR0530
R8 10k NiCD + CELL
VBKUP
DCDIV
RDC1 12.1k 1%
ROHM DTA144E
5VCC FROM DC/DC
Si4936DY SW E SW F
0.1µF
(BOLD LINES INDICATE HIGH CURRENT PATHS)
POWER MANAGEMENT µP
C4 1µF 50V
SMBUS RBAT1 RBAT2
D2 MBRS140T BAT1 4 Li-ION SMART BATTERY PACK
+ RBAT1
C6 10µF CERAMIC
CBAT1 10µF SW G Si9926DY
BAT2 4 Li-ION SMART BATTERY PACK
RPROG 3.83k 1% Q1 2N7002
+ RBAT2
R5 300Ω C8 1µF
14, 15 VCC SW 2 7 PROG 3 6 VC BOOST R6 1k C9 0.1µF 1, 7-10, 16
LT1510 SENSE GND
OVP
6 5
BAT CBAT2 10µF
SW H Si9926DY
+
CDCIN 10µF 35V ALUM
DC INPUT (FROM AC ADAPTOR) D4 MBRS140T
C7 0.22µF D3 1N4148
L3*** 33µH R7 649k 0.25% R8 115k 0.25%
11 (CHARGER OUTPUT)
+
CCHG 22µF TANT
*1812LS-105 XKBC, COILCRAFT **DT1608-223, COILCRAFT ***CTX33-2, COILTRONICS 1479 TA03
22
LTC1479
U
TYPICAL APPLICATIONS N Dual Li-Ion Battery Power Management System (Using an LT1511, 3A Charger) RSENSE 0.033Ω
Si4936DY SW A SW B Si4936DY SW C SW D
330Ω
RDC2 205k 1% RDC1 12.1k 1%
GA SAB GB
DCIN
GC SCD GD
GE SEF GF
ROHM DTA144E
5VCC FROM DC/DC
Si4936DY SW E SW F
0.1µF
(BOLD LINES INDICATE HIGH CURRENT PATHS)
SENSE +
+
R2 390k 1% Q2 2N7002
BAT1
LTC1479 R11 470k
BDIV
RB1 121k 1%
VCC GND V + SW C1 0.1µF
+
C14 0.1µF
BATSEL CHGSEL DCINGOOD 3DM
VCCP VGG
+
C3 1µF 50V
+
6 R1 22k
5VCC FROM DC/DC
5 C15 0.1µF
(BACKUP) VCC
100k
GG SG GH SH BATDIS DCIN/BAT CHGMON LOBAT
L1* 1mH C2 2.2µF 16V
8
LBO FB LT1304 7 SHDN 1 3 LBI VIN ILIM GND
D5 BAS16LT1
BAT2 VBAT
R3 100k 1%
4 SW
2
RB2 1.05M 1%
C5 0.1µF
SENSE – VBKUP
DCDIV
D1 L2** 10µH MBR0530
R12 10k NiCD CELL
TO INPUT OF DC/DC CONVERTER
POWER MANAGEMENT µP
C4 1µF 50V
SMBUS RBAT1 RBAT2
D1 MBRS340T
RS4 0.05Ω
BAT1 4 Li-ION SMART BATTERY PACK
C6 10µF CERAMIC
+ RBAT1
C8 1µF
RBAT2
CBAT2 10µF
R4 500Ω
SW H Si9926DY
9
19 CLN VCC CLP 6 UV PROG 18 2 SW VC R6 3 11 COMP1 BOOST 1k R5 C10 500Ω 200pF LT1511 18 C9 SPIN 1, 4, 5, 7, 0.33µF 16, 23, 24 8 GND OVP BAT SENSE
Q1 2N7002
RS2 200Ω 1% (CHARGER OUTPUT)
+
14 12 RS1 0.033Ω
RS3 200Ω 1%
CCHG 22µF TANT
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
R10 5k
+
CDCIN 10µF 35V ALUM
R9 6.8k
20 TO 22 10
RPROG 4.93k 1%
+
C12 1µF
C7 10µF
CBAT1 10µF SW G Si9926DY
BAT2 4 Li-ION SMART BATTERY PACK
+
DC INPUT (FROM AC ADAPTOR)
D2 MBRS340T C13 0.47µF D3 MBR0540T
L3*** 20µH
C11 50pF
*1812LS-105 XKBC, COILCRAFT **DT1608-223, COILCRAFT ***CTX20-4, COILTRONICS
R7 649k 0.25% R8 115k 0.25%
1479 TA04
23
LTC1479
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted. G Package 36-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640)
0.499 – 0.509* (12.67 – 12.93) 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
0.301 – 0.311 (7.65 – 7.90)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0.205 – 0.212** (5.20 – 5.38)
0.068 – 0.078 (1.73 – 1.99)
0° – 8°
0.005 – 0.009 (0.13 – 0.22)
0.022 – 0.037 (0.55 – 0.95)
0.0256 (0.65) BSC
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.002 – 0.008 (0.05 – 0.21)
0.010 – 0.015 (0.25 – 0.38)
G36 SSOP 1196
RELATED PARTS PART NUMBER
DESCRIPTION
COMMENTS
LT1304
Micropower DC/DC Step-Up Converter
5V at 200mA from 2 Cells, IQ = 10µA in Shutdown
LTC1435
High Efficiency Synchronous Step-Down Converter
Fixed Frequency, Ultrahigh Efficiency
LTC1438
Dual High Efficiency Synchronous Step-Down Converter
Fixed Frequency, PLL Lockable, Ultrahigh Efficiency
LTC1473
Dual PowerPath Switch Driver
Protected Power Management Building Block
LT1510
Constant-Voltage/Constant-Current Battery Charger
1.5A Internal Switch, Precision 0.5% Reference
LT1511
Constant-Voltage/Constant-Current 3A Battery Charger
Adapter Current Limit Loop
LTC1538-AUX
Dual, Synchronous Controller with Aux Regulator
5V Standby in Shutdown
LT1620
Battery Charger Current Controller
96% Efficiency When Used with LTC1435
LT1621
Dual Battery Charger Current Controller
For Dual Loop Applications
24
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900 FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com
1479f LT/TP 0697 7K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1996
