Transcript
LT1070/LT1071 5A and 2.5A High Efficiency Switching Regulators DESCRIPTION
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FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■
Wide Input Voltage Range: 3V to 60V Low Quiescent Current: 6mA Internal 5A Switch (2.5A for LT1071) Very Few External Parts Required Self Protected Against Overloads Operates in Nearly All Switching Topologies Shutdown Mode Draws Only 50µA Supply Current Flyback Regulated Mode Has Fully Floating Outputs Comes in Standard 5-Pin Packages Can be Externally Synchronized (Consult Factory)
U APPLICATIONS ■ ■ ■ ■ ■ ■ ■
Logic Supply 5V at 10A 5V Logic to ±15V Op Amp Supply Off-Line Converter Up to 200W Battery Upconverter Power Inverter (+ to –) or (– to +) Fully Floating Multiple Outputs For Lower Current Applications, See the LT1072
USER NOTE: This data sheet is only intended to provide specifications, graphs and a general functional description of the LT1070/LT1071. Application circuits are included to show the capability of the LT1070/LT1071. A complete design manual (AN19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1071 by factoring in the lower switch current rating. A second Application Note, AN25, which details off-line applications is available.
The LT ®1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and “Cuk”. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the LT1070/LT1071 to be built in a standard 5-pin TO-3 or T0-220 power package. This makes it extremely easy to use and provides “bust proof” operation similar to that obtained with 3-pin linear regulators. The LT1070/LT1071 operate with supply voltages from 3V to 60V, and draw only 6mA quiescent current. They can deliver load power up to 100W with no external power devices. By utilizing current mode switching techniques, they provide excellent AC and DC load and line regulation. The LT1070/LT1071 have many unique features not found even on the vastly more difficult to use low power control chips presently available. They use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 50µA typical for standby operation. Totally isolated and regulated outputs can be generated by using the optional “flyback regulation mode” built into the LT1070/LT1071, without the need for optocouplers or extra transformer windings. , LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATION
Maximum Output Power*
Boost Converter (5V to 12V)
100
L2 10µH
80
L1** 150µH
OUTPUT FILTER
C3 100µF
D1 VIN C3* 100µF
+
+
LT1070 GND
VC
12V 1A
VSW C2 1000µF
R1 10.7k 1%
POWER (W)**
BOOST 5V
BUCK/BOOST VO = 30V
60
FLYBACK 40 ISOLATED 20 BUCK/BOOST VO = 5V
FB R3 1k C1 1µF
*REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113
R2 1.24k 1%
0
0
10
30 20 INPUT VOLTAGE (V)
40
50 1070/71 TA02
1070/71 TA01
*ROUGH GUIDE ONLY. BUCK MODE POUT = 5A • VOUT. SPECIAL TOPOLOGIES DELIVER MORE POWER **DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071
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LT1070/LT1071
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage LT1070/LT1071 (Note 2) .................................... 40V LT1070HV/LT1071HV (Note 2)........................... 60V Switch Output Voltage LT1070/LT1071 .................................................. 65V LT1070HV/LT1071HV......................................... 75V Feedback Pin Voltage (Transient, 1ms) ................ ±15V
Operating Junction Temperature Range Commercial (Operating) ....................... 0°C to 100°C Commercial (Short Circuit)................... 0°C to 125°C Industrial ......................................... – 40°C to 125°C Military ............................................ – 55°C to 150°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C
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PACKAGE/ORDER INFORMATION VSW
VC 1
4
2
CASE IS GND
3
VIN
ORDER PART NUMBER
ORDER PART NUMBER
BOTTOM VIEW
FB K PACKAGE 4-LEAD TO-3 METAL CAN
TJMAX = 100°C, θJA = 35°C/ W, QJC = 2°C (LT1070C, I) TJMAX = 150°C, θJA = 35°C/ W, QJC = 2°C (LT1070M) TJMAX = 100°C, θJA = 35°C/ W, QJC = 4°C (LT1071C, I) TJMAX = 150°C, θJA = 35°C/ W, QJC = 4°C (LT1071M)
LT1070CK LT1070HVCK LT1070HVMK LT1070IK LT1070MK LT1071CK LT1071HVCK LT1071HVMK LT1071MK
ELECTRICAL CHARACTERISTICS
FRONT VIEW 5
VIN
4
VSW
3
GND
2
FB
1
VC
LT1070CT LT1070HVCT LT1070HVIT LT1070IT LT1071CT LT1071HVCT LT1071HVIT LT1071IT
T PACKAGE 5-LEAD PLASTIC TO-220
TJMAX = 100°C, θJA = 75°C/ W, QJC = 2°C (LT1070C, I) TJMAX = 100°C, θJA = 75°C/ W, QJC = 4°C (LT1071C)
VIN = 15V, VC = 0.5V, VFB = VREF, output pin open unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VREF
Reference Voltage
Measured at Feedback Pin, VC = 0.8V
1.224 1.214
1.244 1.244
1.264 1.274
V V
350
750 1100
nA nA
●
IB
Feedback Input Current
VFB = VREF ●
gm
Error Amplifier Transconductance Error Amplifier Source or Sink Current Error Amplifier Clamp Voltage
AV
∆IC = ±25µA
6000 7000
µmho µmho
150 120
200
●
350 400
µA µA
2.30 0.52
V V
0.03
%/V
VC = 1.5V Hi Clamp, VFB = 1V Lo Clamp, VFB = 1.5V
Reference Voltage Line Regulation
3V ≤ VIN ≤ VMAX, VC = 0.8V
Error Amplifier Voltage Gain
0.9V ≤ VC ≤ 1.4V
Minimum Input Voltage IQ
3000 2400
4400
●
1.80 0.25 ●
500
3V ≤ VIN ≤ VMAX, VC = 0.6V
Control Pin Threshold
Duty Cycle = 0 ●
Normal/Flyback Threshold on Feedback Pin
2
800
V/V
2.6
3.0
6
9
0.8 0.6
0.9
1.08 1.25
V V
0.4
0.45
0.54
V
●
Supply Current
0.38
V mA
LT1070/LT1071
ELECTRICAL CHARACTERISTICS
VIN = 15V, VC = 0.5V, VFB = VREF, output pin open unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
VFB
Flyback Reference Voltage
IFB = 50µA ●
Change in Flyback Reference Voltage
BV
VSAT
ILIM
0.05 ≤ IFB ≤ 1mA
Flyback Reference Voltage Line Regulation
IFB = 50µA, 3V ≤ VIN ≤ VMAX (Note 3)
Flyback Amplifier Transconductance (gm)
∆IC = ±10µA
Flyback Amplifier Source and Sink Current
VC = 0.6V, IFB = 50µA (Source) VC = 0.6V, IFB = 50µA (Sink)
Output Switch Breakdown Voltage
TYP
MAX
UNITS
15 14
16.3
17.6 18.0
V V
4.5
6.8
8.5
V
0.01
0.03
%/V
150
300
650
µmho
● ●
15 25
32 40
70 70
µA µA
3V ≤ VIN ≤ VMAX, ISW = 1.5mA (LT1070/LT1071) (LT1070HV/LT1071HV)
● ●
65 75
90 90
Output Switch “On” Resistance (Note 4)
LT1070 LT1071
● ●
Control Voltage to Switch Current Transconductance
LT1070 LT1071
Switch Current Limit (LT1070)
Duty Cycle ≤ 50%, TJ ≥ 25°C Duty Cycle ≤ 50%, TJ < 25°C Duty Cycle = 80% (Note 5)
● ● ●
5 5 4
10 11 10
A A A
Switch Current Limit (LT1071)
Duty Cycle ≤ 50%, TJ ≥ 25°C Duty Cycle ≤ 50%, TJ < 25°C Duty Cycle = 80% (Note 5)
● ● ●
2.5 2.5 2.0
5.0 5.5 5.0
A A A
25
35
mA/A
40
45 47
kHz kHz
92
97
∆IIN ∆ISW
Supply Current Increase During Switch “On” Time
f
Switching Frequency
0.15 0.30
Maximum Switch Duty Cycle
35 33 90
Flyback Sense Delay Time
Ω Ω
0.24 0.50
A/V A/V
% µs
1.5
Shutdown Mode Supply Current
3V ≤ VIN ≤ VMAX, VC = 0.05V
Shutdown Mode Threshold Voltage
3V ≤ VIN ≤ VMAX ●
The ● denotes the specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Minimum switch “on” time for the LT1070/LT1071 in current limit is ≈1µs. This limits the maximum input voltage during short-circuit conditions, in the buck and inverting modes only, to ≈ 35V. Normal (unshorted) conditions are not affected. Mask changes are being implemented which will reduce minimum “on” time to ≤ 1µs, increasing maximum short-circuit input voltage above 40V. If the present LT1070/LT1071 (contact factory for package date code) is being operated in the buck or inverting mode at high input voltages and short-circuit conditions are expected, a resistor must be placed in series with the inductor, as follows: The value of the resistor is given by: R=
V V
8 4
●
DC (Max)
MIN
100 50
100
250
µA
150
250 300
mV mV
t = Minimum “on” time of LT1070/LT1071 in current limit, ≈1µs f = Operating frequency (40kHz) VF = Forward voltage of external catch diode at ILIMIT ILIMIT = Current limit of LT1070 (≈ 8A), LT1071 (≈ 4A) RL = Internal series resistance of inductor Note 3: VMAX = 55V for LT1070HV and LT1071HV to avoid switch breakdown. Note 4: Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1070 and 2A for LT1071. Note 5: For duty cycles (DC) between 50% and 80%, minimum guaranteed switch current is given by ILIM = 3.33 (2 – DC) for the LT1070 and ILIM = 1.67 (2 – DC) for the LT1071.
t • f • VIN – VF – RL ILIMIT
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LT1070/LT1071 U W
TYPICAL PERFORMANCE CHARACTERISTICS Switch Current Limit vs Duty Cycle
Maximum Duty Cycle
16 FOR LT1071, DIVIDE VERTICAL SCALE BY 2
96
2.2
95
2.0
94
1.8
10 – 55°C
25°C
8 125°C
6
TIME (µs)
12 DUTY CYCLE (%)
93
2 0
92
1.4
91
1.2
10 20 30 40 50 60 70 80 90 100 DUTY CYCLE (%)
90 –75 – 50 – 25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (°C)
1.0 –75 – 50 – 25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (°C)
1070/71 G01
1070/71 G02
1.6
2.9 SWITCH SATURATION VOLTAGE (V)
SWITCH CURRENT = 5A
MINIMUM INPUT VOLTAGE (V)
Isolated Mode Flyback Reference Voltage
Switch Saturation Voltage
Minimum Input Voltage
2.8 2.7 2.6 SWITCH CURRENT = 0A 2.5 2.4 2.3 –75 – 50 – 25
1.4
22 150°C
1.2 100°C 1.0 25°C
0.8
– 55°C 0.6 0.4 0.2 0
0 25 50 75 100 125 150 TEMPERATURE (°C)
23
FOR LT1071, DIVIDE CURRENT BY 2
0
1
4 5 2 3 6 SWITCH CURRENT (A)
7
1.248 REFERENCE VOLTAGE (V)
TJ = – 55°C
–1 –2
–4 –5 10
30 40 20 INPUT VOLTAGE (V)
50
60
1070/71 G07
4
RFEEDBACK = 10k
0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G06
1.246
SWITCHING FREQUENCY
800
41
700
40
1.244 1.242
42
39 REFERENCE V0LTAGE
38
1.240
37
1.238
36
1.236
35
–3
0
17
15 – 75 – 50 – 25
8
1.234 – 75 – 50 – 25
34 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G08
SWITCHING FREQUENCY (kHz)
1 0
18
Feedback Bias Current vs Temperature
1.250
4
TJ = 25°C
RFEEDBACK = 1k
19
Reference Voltage vs Temperature
5
2
20
1070/71 G05
Line Regulation
TJ = 150°C
RFEEDBACK = 500Ω
21
16
1070/71 G04
3
1070/71 G03
FLYBACK VOLTAGE (V)
0
REFERENCE VOLTAGE CHANGE (mV)
1.6
4
FEEDBACK BIAS CURRENT (nA)
SWITCH CURRENT (A)
14
Flyback Blanking Time
600 500 400 300 200 100 0 – 75 – 50 – 25
0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G09
LT1070/LT1071 U W
TYPICAL PERFORMANCE CHARACTERISTICS 160
16
INPUT CURRENT (mA)
80 TJ = – 55°C TJ ≥ 25°C
40
12 11 50% DUTY CYCLE
10 9
10% DUTY CYCLE
8
20 0 1
0
4 2 3 SWITCH CURRENT (A)
0
10
1070/71 G10
Normal/Flyback Mode Threshold on Feedback Pin
60 40
30 40 20 INPUT VOLTAGE (V)
50
60
Shutdown Mode Supply Current
490
–22
180
4500
480
–20
470
–18
–14
440
–12
430
–10 FEEDBACK PIN CURRENT (AT THRESHOLD)
420
140 120
TJ = 150°C
100 80 60
– 55°C ≤ TJ ≤ 125°C
40
–6
20
–4 25 50 75 100 125 150 0 TEMPERATURE (°C)
0
410 400 –50 –25
–8
160
SUPPLY CURRENT (µA)
450
0
–250
200
–200 VOLTAGE
150
–150
100
–100 VC VOLTAGE IS REDUCED UNTIL REGULATOR CURRENT DROPS BELOW 300µA
– 50
0 0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G16
IDLE SUPPLY CURRENT (mA)
250
VC PIN CURRENT (µA)
–300
0 – 75 – 50 – 25
10
–350
300
50
11
– 400
60
gm = ∆I (VC PIN) ∆V (FB PIN)
3500 3000 2500 2000 1500 1000
0 –75 – 50 –25
10 20 30 40 50 60 70 80 90 100 VC PIN VOLTAGE (mV)
0 25 50 75 100 125 150 TEMPERATURE (°C) 1070/71 G14
1070/71 G14
Shutdown Thresholds CURRENT (OUT OF VC PIN)
50
4000
Idle Supply Current vs Temperature
400
20 40 30 SUPPLY VOLTAGE (V)
500
1070/71 G13
350
TRANSCONDUCTANCE (µmho)
5000
–16
10
Error Amplifier Transconductance
200
FEEDBACK PIN VOLTAGE (AT THRESHOLD)
0
1070/71 G12
–24
460
VC = 0V
1070/71 G11
500
FEEDBACK PIN CURRENT (µA)
FEEDBACK PIN VOLTAGE (mV)
VC = 50mV 80
*UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH 10% OR LESS
*AVERAGE LT1070 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT
VC PIN VOLTAGE (mV)
100
0
6
5
120
20
0% DUTY CYCLE
7
Feedback Pin Clamp Voltage 500
VC = 0.6V
450
9
FEEDBACK VOLTAGE (mV)
DRIVER CURRENT (mA)
100
ISWITCH ≤ 10mA
13
TJ = 25°C
140
90% DUTY CYCLE
14
120
160
TJ = 25°C
15
140
60
Supply Current vs Supply Voltage (Shutdown Mode)
Supply Current vs Input Voltage*
SUPPLY CURRENT (µA)
Driver Current* vs Switch Current
8 7 6 5
VSUPPLY = 60V VSUPPLY = 3V
4
400
250
150
2
50 0
1070/71 G14
150°C
200
100
0 25 50 75 100 125 150 TEMPERATURE (°C)
25°C
300
3
1 –75 – 50 –25
– 55°C
350
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK CURRENT (mA) 1070/71 G18
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LT1070/LT1071 U W
TYPICAL PERFORMANCE CHARACTERISTICS Switch “Off” Characteristics
Transconductance of Error Amplifier
VC Pin Characteristics 300
1000 900
6000
VC PIN CURRENT (µA)
SWITCH CURRENT (µA)
600 500
VSUPPLY =
400 3V
300
15V
40V
55V
VFB = 1.5V (CURRENT INTO VC PIN)
100 0 –100
VFB = 0.8V (CURRENT OUT OF VC PIN)
– 200
200
– 300
100 0
10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V)
30
5000 gm
4000
0
0.5
2.0 1.5 1.0 VC PIN VOLTAGE (V)
1070/71 G19
2.5
60
3000
90
2000
120
1000
150
0
180
–1000
– 400 0
0
θ
1k
10k
100k 1M FREQUENCY (Hz)
PHASE (°)
TRANSCONDUCTANCE (µmho)
200
800 700
– 30
7000
TJ = 25°C
210 10M 1070/71 G21
1070/71 G20
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BLOCK DIAGRAM
16V SWITCH OUT
VIN 2.3V REG
FLYBACK ERROR AMP
40kHz OSC
LOGIC
MODE SELECT
DRIVER
5A, 75V SWITCH
ANTISAT COMP
–
FB
ERROR
VC
+ AMP
+ CURRENT AMP
SHUTDOWN CIRCUIT 1.24V REF
0.15V
GAIN ≈ 6
0.02Ω (0.04Ω LT1071)
–
1070/71 BD
U OPERATION The LT1070/LT1071 is a current mode switcher. This means that switch duty cycle is directly controlled by switch current rather than by output voltage. Referring to the Block Diagram, the switch is turned “on” at the start of each oscillator cycle. It is turned “off” when switch current reaches a predetermined level. Control of output
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voltage is obtained by using the output of a voltage sensing error amplifier to set current trip level. This technique has several advantages. First, it has immediate response to input voltage variations, unlike ordinary switchers which have notoriously poor line transient response. Second, it reduces the 90° phase shift at
LT1070/LT1071 U OPERATION midfrequencies in the energy storage inductor. This greatly simplifies closed-loop frequency compensation under widely varying input voltage or output load conditions. Finally, it allows simple pulse-by-pulse current limiting to provide maximum switch protection under output overload or short-circuit conditions. A low dropout internal regulator provides a 2.3V supply for all internal circuitry of the LT1070/LT1071. This low dropout design allows input voltage to vary from 3V to 60V with virtually no change in device performance. A 40kHz oscillator is the basic clock for all internal timing. It turns “on” the output switch via the logic and driver circuitry. Special adaptive antisat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneously to limit switch saturation. This minimizes driver dissipation and provides very rapid turn-off of the switch. A 1.2V bandgap reference biases the positive input of the error amplifier. The negative input is brought out for output voltage sensing. This feedback pin has a second function; when pulled low with an external resistor, it programs the LT1070/LT1071 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. The LT1070/ LT1071 will then regulate the value of the flyback pulse with respect to the supply voltage. This flyback pulse is directly proportional to output voltage in the traditional
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TYPICAL APPLICATIONS
transformer coupled flyback topology regulator. By regulating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection between input and output. The output is fully floating up to the breakdown voltage of the transformer windings. Multiple floating outputs are easily obtained with additional windings. A special delay network inside the LT1070/ LT1071 ignores the leakage inductance spike at the leading edge of the flyback pulse to improve output regulation. The error signal developed at the comparator input is brought out externally. This pin (VC) has four different functions. It is used for frequency compensation, current limit adjustment, soft starting and total regulator shutdown. During normal regulator operation this pin sits at a voltage between 0.9V (low output current) and 2.0V (high output current). The error amplifiers are current output (gm) types, so this voltage can be externally clamped for adjusting current limit. Likewise, a capacitor coupled external clamp will provide soft start. Switch duty cycle goes to zero if the VC pin is pulled to ground through a diode, placing the LT1070/LT1071 in an idle mode. Pulling the VC pin below 0.15V causes total regulator shutdown, with only 50µA supply current for shutdown circuitry biasing. See AN19 for full application details.
(Note that maximum output currents are divided by 2 for the LT1071) Driving High Voltage NPN C1
Driving High Voltage FET (for Off-Line Applications, See AN25)
VIN
10V TO 20V
+
VSW
LT1070/LT1071
GND
1070/71 TA03
G
D
D1
S
D2
R2** R1*
Q1
Q1 D1 VIN
VSW
LT1070/LT1071
*SETS IB(ON) **SETS IB(OFF)
GND
1070/71 TA16
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LT1070/LT1071
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TYPICAL APPLICATIONS
(Note that maximum output currents are divided by 2 for the LT1071) Negative Buck Converter
D1 VIN C3 100µF
+ L1** 200µH
C2 1000µF
– 5.2V 4.5A
Q1 2N3906
LT1070
FB
VC
GND
LOAD
VSW
+
OPTIONAL INPUT FILTER
R1 4.64k
L3
OPTIONAL OUTPUT FILTER
C1 R2 1.24k
R3 VIN – 20V
+
C4 200µF
L2 4µH
*REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113
1070/71 TA12
Positive Buck Converter VIN D3
L2 4µH VIN
+ C5*
C3 2.2µF
OPTIONAL OUTPUT FILTER
VSW
+ LT1070
D2 1N914
R1 3.74k
100µF
VC
GND
C5 200µF
FB R2 1.24k
R3 470Ω C1 1µF
+
C2 1µF
R4 10Ω
L1** 100µH
r
+
D1
C4 1000µF
*REQUIRED IF INPUT LEADS ≥2" **PULSE ENGINEERING 92112
5V 4.5A 100mA MINIMUM 1070/71 TA14
Negative Current Boosted Buck Converter + C1
R1 R5
C3
• VIN
+
VSW
T1 1:N D1
•
Q1 2N3906
R4 12k R1 =
LT1070
GND
VC
FB R3
R2 1.24k
C2 – VIN
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MINIMUM LOAD = 10mA
1070/71 TA13
VOUT – 0.6V 1mA
– VOUT 5V 10A
LT1070/LT1071
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TYPICAL APPLICATIONS
(Note that maximum output currents are divided by 2 for the LT1071) Positive Current Boosted Buck Converter
VIN 28V
470Ω 2W
R6 470Ω
C3 0.47µF
C6 0.002µF
D2
VIN
•
1:N
VSW
N ≈ 0.25
LT1070 R2 1k GND
R7 1.24k
D1
FB
VC
VIN 7 6
C5* 100µF
–
R3 680Ω
+
•
+
2
V V – LM308 COMP 3 4
R5 5k
+
C1 0.33µF
8
R4 1.24k
200pF
R1 5k
*REQUIRED IF INPUT LEADS ≥ 2"
VOUT 5V 10A
+
C2 5000µF 1070/71 TA19
Positive to Negative Buck/Boost Converter
Negative to Positive Buck/Boost Converter
L1** 150µH
OPTIONAL OUTPUT FILTER
C3 VIN
D1 VIN C4* 100µF
VSW C2 1000µF
+ LT1070
+
R1 11.3k Q1
L3 GND OPTIONAL INPUT FILTER VIN – 12V
VC
FB R3 2.2k C1 0.22µF
R2 1.24k
R5† 470Ω 1W
D3† 1N4001
L2
VOUT 12V 2A
C4 5µF
VSW
+ LT1070
GND
VC
†
TO AVOID START-UP PROBLEMS FOR INPUT VOLTAGES BELOW 10V, VIN 10V TO 30V CONNECT ANODE OF D3 TO VIN AND REMOVE R5. C5* C1 MAY BE REDUCED FOR 100µF LOWER OUTPUT CURRENTS. C1 ≈ (500µF)(IOUT) FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO 0.3µF D2 R1 R4 1N914 47Ω AND REDUCE R6 TO 100Ω. 10.7k
FB R3 5k C1 0.1µF
R2 1.24k
+
C3 C1† 2µF 1000µF
+
R6 470Ω
D1 1070/71 TA09
1070/71 TA05
L1** 200µH
*REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113
VOUT – 12V 2A
*REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING 92113
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LT1070/LT1071
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TYPICAL APPLICATIONS
(Note that maximum output currents are divided by 2 for the LT1071) Current Boosted Boost Converter
Voltage Boosted Boost Converter R4 680Ω 1W
C3 0.68µF
R4
D2 VIN
+
VIN 15V
VSW
LT1070
VC
R3 10k C2 0.047µF
VIN VIN 16V TO 24V
+
R2 1.24k
D1
VOUT 28V 4A
N
VSW
+
R1 27k LT1070
+ C1
VOUT 100V 300mA
FB
I
D2
D1
R1 98k GND
TOTAL INDUCTANCE = 4mH INTERLEAVE PRIMARY AND SECONDARY FOR LOW LEAKAGE INDUCTANCE
1 L1 N=5
C3
VC
GND
C1 200µF
FB R2 1.24k
R3 C2
1070/71 TA10
1070/71 TA11
Negative Input/Negative Output Flyback Converter
Negative Boost Regulator D2
VSW
C4* 470µF
VIN –15V
VIN
+
R1 27k
+ GND
L1 200µH
R6
•
VIN
LT1070
+
C3
R3 3.3k C2 0.22µF
RO (MINIMUM LOAD)
+
VC
FB
*R1 = R4 1.24k
R5
*REQUIRED IF INPUT LEADS ≥ 2"
VOUT –28V 1A
C2 1070/71 TA17
– VIN 1070/71 TA15
External Current Limit
External Current Limit
VSW
VX LT1070/LT1071
LT1070/LT1071
R2
+
= 2V
VIN
FB GND R1 1k
Q1 C1 1000pF RS
10
D1
VC
GND
VC
R1 500Ω R2 1070/71 TA04
C2
C1
– VOUT GND
D1
+
Q1 2N3906
LT1070/LT1071
R2 1.24k
VIN
•
R1*
C3 10µF
FB
VC
C1 1000µF
T1 1:N
VSW
R2 5k
R3 1k
NOTE THAT THE LT1070/LT1071 GND PIN IS NO LONGER COMMON TO VIN– 1070/71 TA06
VOUT – 1.6V 200µA
LT1070/LT1071
U
TYPICAL APPLICATIONS
(Note that maximum output currents are divided by 2 for the LT1071) Flyback Converter CLAMP TURN-ON SPIKE
VSNUB L2 10µH C4 200µF
OPTIONAL FILTER D1 VIN 20V TO 30V
C3 0.47µF
R4
+
(N)(VIN) SECONDARY VOLTAGE AREA “c” = AREA “d” TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY
c 0V d
C1 2000µF
∆I IPRI R1 3.74k
PRIMARY CURRENT
0 IPRI N
SECONDARY CURRENT
0
FB
IPRI
VC R2 1.24k
R3 1.5k C2 0.15µF
LT1070 SWITCH CURRENT
0 IPRI
SNUBBER DIODE CURRENT
*REQUIRED IF INPUT LEADS ≥ 2"
1070/71 TA08
(I )(L ) t = PRI L VSNUB
U
PACKAGE DESCRIPTION
0.320 – 0.350 (8.13 – 8.89)
VOUT + VF
VSW
LT1070
GND
b
0V
• N = 1/3
C4* 100µF
VOUT 5V 6A
1 N
D2
VIN
+
•
+ VF V PRIMARY FLYBACK VOLTAGE = OUT N LT1070/LT1071 SWITCH VOLTAGE AREA “a” = AREA “b” TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY
a VIN
Dimensions in inches (millimeters) unless otherwise noted.
K Package 4-Lead TO-3 Metal Can
T Package 5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1311)
(LTC DWG # 05-08-1421)
0.760 – 0.775 (19.30 – 19.69)
0.390 – 0.415 (9.906 – 10.541) 0.060 – 0.135 (1.524 – 3.429)
0.165 – 0.180 (4.191 – 4.572)
0.147 – 0.155 (3.734 – 3.937) DIA
0.045 – 0.055 (1.143 – 1.397)
0.230 – 0.270 (5.842 – 6.858) 0.420 – 0.480 (10.67 – 12.19)
0.460 – 0.500 (11.684 – 12.700) 0.038 – 0.043 (0.965 – 1.09)
0.570 – 0.620 (14.478 – 15.748) 0.330 – 0.370 (8.382 – 9.398)
0.620 (15.75) TYP
0.700 – 0.728 (17.78 – 18.491)
1.177 – 1.197 (29.90 – 30.40)
0.470 TP P.C.D.
0.655 – 0.675 (16.64 – 19.05) 0.151 – 0.161 (3.84 – 4.09) DIA 2 PLC 0.167 – 0.177 (4.24 – 4.49) R
72° 18°
0.152 – 0.202 0.260 – 0.320 (3.861 – 5.131) (6.60 – 8.13)
0.095 – 0.115 (2.413 – 2.921)
0.013 – 0.023 (0.330 – 0.584) 0.057 – 0.077 (1.448 – 1.956)
0.028 – 0.038 (0.711 – 0.965)
0.135 – 0.165 (3.429 – 4.191)
0.155 – 0.195 (3.937 – 4.953) T5 (TO-220) 0398
0.495 – 0.525 (12.57 – 13.34) R
K4(TO-3) 0695
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.
11
LT1070/LT1071
U
TYPICAL APPLICATIONS
(Note that maximum output currents are divided by 2 for the LT1071) Totally Isolated Converter OPTIONAL OUTPUT FILTER D1
15V
1:N C3 0.47µF
R4 1.5k
+
•
+
N VIN
+V
+
IN
5V
C5* 100µF
LT1070/LT1071
COM
C4 500µF
•
VSW
+
C1 500µF
N
L1 10µF
–15V
C6 200µF
N = 0.875 = 7:8 FOR VOUT = 15V ≈16V SWITCH VOLTAGE
FB VC
GND
+
L2 10µF
C5 200µF
VIN
500Ω
tOFF
0V
tON
R2
C2 5k 0.01µF
VF (DIODE FORWARD VOLTAGE)
VOUT
SECONDARY VOLTAGE
0V *REQUIRED IF INPUT LEADS ≥ 2"
1070/71 TA07
(N)(VIN)
Forward Converter
R4
C2
•
I
L1 70µH
D1
T1 M
N
•
+ D2
VIN
VIN 20V TO 30V
D3
VC
C1 2000µF
•
VSW
LT1070
GND
VOUT 5V 6A
D4
R1 3.74k
FB Q1 R3 C3
R6 C4 330Ω
R5 1Ω
R2 1.24k
1070/71 TA18
RELATED PARTS PART NUMBER
DESCRIPTION
COMMENTS
LT1074/LT1076
High Voltage Switching Regulators
40V Input (60V for HV Versions), 100kHz, 5A and 2A
LT1170/LT1171/ LT1172
100kHz High Efficiency Switching Regulators
40V Input (65V for HV Versions), 5A/2.5A/1.25A Internal Switch
LT1370/LT1371
500kHz High Efficiency Switching Regulators
35V, 6A/3A Internal Switch
LT1374/LT1376
100kHz High Efficiency Switching Regulators
25V Input, 4.5A/1.5A Internal Switch
12
Linear Technology Corporation
10701fd LT/TP 1098 2K REV D • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1989
