Transcript
IRDC3894-P5V0
SupIRBuck
TM
USER GUIDE FOR IR3894 EVALUATION BOARD 5.0Vout DESCRIPTION
The IR3894 is a synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mm X 6 mm Power QFN package. Key features offered by the IR3894 include internal Digital Soft Start/Soft Stop, precision 0.5Vreference voltage, Power Good, thermal protection, programmable switching frequency, Enable input, input under-voltage lockout for proper start-up, enhanced line/ load regulation with feed forward, external frequency synchronization with smooth clocking, smart internal LDO and pre-bias start-up.
Output over-current protection function is implemented by sensing the voltage developed across the on-resistance of the synchronous rectifier MOSFET for optimum cost and performance and the current limit is thermally compensated. This user guide contains the schematic and bill of materials for the IR3894 evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3894 is available in the IR3894 data sheet.
BOARD FEATURES • Vin = +12V (+ 13.2V Max) • Vout = +5.0V @ 0- 10A • Fs= 600kHz • L= 1.5uH • Cin= 4x10uF (ceramic 1206) + 1x330uF (electrolytic)* • Cout= 2x22uF (ceramic 1206) * The 330uF input capacitor is placed for damping the parasitic inductance of bench power supply wires. It is not required for the POL applications where input is delivered with power planes. 3/28/2013
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IRDC3894-P5V0 CONNECTIONS AND OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 10A load should be connected to VOUT+ and VOUT-. The input and output connections of the board are listed in Table I. IR3894 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc is required, then R15 can be removed and external Vcc can be applied between Vcc+ and Vcc- pins. Vin pin and Vcc/LDOout pins should be shorted together for external Vcc operation (use zero ohm resistor for R29). The output can track voltage at the Vp pin. For this purpose, Vref pin is to be connected to ground (use zero ohm resistor for R21). The value of R14 and R28 can be selected to provide the desired tracking ratio between output voltage and the tracking input. Table I. Connections
Connection
Signal Name
VIN+
Vin (+12V)
VIN-
Ground of Vin
Vout+
Vout(+5.0V)
Vout-
Ground for Vout
Vcc+
Vcc/ LDO_out Pin
Vcc-
Ground for Vcc input
Enable
Enable
PGood
Power Good Signal
Gnd
Analog ground
LAYOUT The PCB is a 4-layer board (2.23”x2”) using FR4 material. All layers use 2 Oz. copper. The PCB thickness is 0.062”. The IR3894 and other major power components are mounted on the top side of the board. Power supply decoupling capacitors, the bootstrap capacitor and feedback components are located close to IR3894. The feedback resistors are connected to the output at the point of regulation and are located close to the SupIRBuck IC. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. 3/28/2013
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IRDC3894-P5V0 Vin
Gnd
Gnd
Vout
Enable
Top View
VDDQ Vref Sync PGood
AGnd S_Ctrl Vsns Vcc+ Vcc-
Bottom View
Fig. 1: Connection Diagram of IR3895/94 Evaluation Boards
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IRDC3894-P5V0
Fig. 2: Board Layout-Top Layer
Single point connection between Analog Gnd and PGnd
Fig. 3: Board Layout-Bottom Layer
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IRDC3894-P5V0
Fig. 4: Board Layout-Mid Layer 1
Fig. 5: Board Layout-Mid Layer 2 3/28/2013
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N/S
VCC
N/S
C10
R17 49.9k
Vcc+
N/S
R28
R14 N/S
C11
39.2k
N/S
15nF C31
C26
R1 1.33k
R9
220pF
C12 0.1nF
R13 0
C21 C23 N/S 2.2uF
VCC
S_Ctrl
Vp
Rt_Sy nc
AGnd
COMP
FB
15
C32 1.0uF
IR3894
R7 N/S
11
12
C8
PGND
C7 0.1uF
13
R3 0.487k
4.42k
R2
143 Ohm 2200pF
R4
PGnd
SW
PVin
U1
R10 0
A
L1 1.5uH
C25 N/S
R6 20
B
R12 0.487k
R11 4.42k
Cyntec Inductor (PIMB104T-1R5MS)
0.1uF
C24
VCC R29
N/S
R15 0
R50 0
C34 C33 N/S N/S
C30 N/S
Fig. 6: Schematic of the IR3894 evaluation board
6
16
5
4
3
1
N/S
2 VREF
R21 N/S
7.5k
Boot
VDDQ
Vcc-
PGood
C13
1
SY NC
1
1
9 PGood 7
1
1
14 Vsns 8
Agnd
1
GND 17
Enable Vcc/LDO_OUT
10
Vin
49.9k
1
R19 C37
1
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R18
+ C36 N/S
N/S
C28 N/S
+ C35
C29 N/S
C27 N/S
C6 N/S
C20 N/S
C5 10uF
C19 N/S
C4 10uF
C18 N/S
C3
C17 N/S
10uF
C16 22uF
C2 10uF
C1 +
C15 22uF
C14 0.1uF
Vout
330uF/25V
Vin
IRDC3894-P5V0
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IRDC3894-P5V0 Bill of Materials
Item Qty
Part Reference
Value
1 2 3 4 5 6 7 8 9 10
1 4 3 1 1 1 2 1 1 1
C1 C2 C3 C4 C5 C7 C14 C24 C12 C8 C11 C15 C16 C23 C26 C32
330uF 10uF 0.1uF 0.1nF 2200pF 220pF 22uF 2.2uF 15nF 1.0uF
11 12 13 14 15 16 17 18 19 20 21
1 1 2 2 1 1 1 4 2 1 1
L1 R1 R2 R11 R3 R12 R4 R6 R9 R10 R13 R15 R50 R17 R18 R19 U1
1.5uH 1.33k 4.42k 0.487k 143 20 39.2k 0 49.9k 7.5k IR3894
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Description SMD Electrolytic F size 25V 20% 1206, 16V, X5R, 20% 0603, 25V, X7R, 10% 0603, 25V, COG, 5% 0603, 50V,X7R,10% 0603, 50V, COG, 5% 1206, 16V, X5R, 20% 0603, 16V, X5R, 20% 0603, 25V, X7R, 10% 0603, 25V, X5R, 10% SMD 11.15x10x3.8mm,3.8mΩ, Isat. 32A Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% PQFN 5x6mm
Manufactu rer Panasonic
Part Number
TDK Murata Murata Murata Murata Murata TDK Murata Murata
EEV-FK1E331P C3216X5R1C106M160AA GRM188R71E104KA01D GRM0335C1E101JD01D GRM188R71H222KA01D GRM1885C1H221JA01 GRM31CR61C226ME15L C1608X5R1C225M GRM188R71E153KA01 GRM188R61E105KA12D
Cyntec Panasonic Panasonic Panasonic Panasonic Panasonic Yageo Panasonic Panasonic Panasonic IR
PIMB104T-1R5MS ERJ-3EKF1331V ERJ-3EKF4421V ERJ-3EKF4870V ERJ-3EKF1430V ERJ-3EKF20R0V 9C06031A3922FKHFT ERJ-3GEY0R00V ERJ-3EKF4992V ERJ-3EKF7501V IR3894MPBF
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IRDC3894-P5V0 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=5.0V, Iout=0-10A, Room Temperature, no airflow
Fig. 7: Start up at 10A current Ch1: Vin, Ch2: Vout, Ch3: PGood Ch4: Enable
Fig. 8: Start up at 10A current Ch1: Vin, Ch2: Vout, Ch3: PGood, Ch4: Vcc
Fig. 9: Start up with 3V Pre Bias, 0A Load, Ch2: Vout, Ch3: PGood, Ch4: Enable
Fig. 10: Output voltage ripple, 10A current Ch2: Vout
Fig. 11: Inductor node at 10A current Ch3: SW node
Fig. 12: Short circuit (Hiccup) recovery Ch2:Vout, Ch3: PGood
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IRDC3894-P5V0 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout= 5.0V, Iout=0-10A, Room Temperature, no air flow
(a)
(b) Fig. 13: Transient response for 2A steps at 1A/us rising/falling slew rates: (a) 0A to 2A and back to 0A, (b) 6A to 8A and back to 6A. Ch2:Vout Ch4:Iout
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IRDC3894-P5V0
40
200
30
150
20
100
10
50 0
0
TR2/°
TR1/dB
TYPICAL OPERATING WAVEFORMS Vin= 12.0V, Vout= 5.0V, Iout= 0A-10A, 600kHz, Room Temperature, No air flow
-10
-50
-20
-100
-30
-150
-40
103
104
105
-200
f/Hz TR1: Mag(Gain)
TR2: Unwrapped Phase(Gain)
Fig. 14: Bode Plot at 10A load shows a bandwidth of 80.37kHz and phase margin of 58.77 degrees
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IRDC3894-P5V0 TYPICAL OPERATING WAVEFORMS Vin= 12.0V, Vout= 5.0V, Iout= 0A-10A, Room Temperature, no air flow
Fig.15: Efficiency versus load current
Fig.16: Power loss versus load current 3/28/2013
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IRDC3894-P5V0 THERMAL IMAGES Vin= 12.0V, Vout= 5.0V, Iout= 0A-10A, 600kHz, Room Temperature, No airflow
Fig. 17: Thermal Image of the board at 10A load IR3894: 93.290C Inductor: 57.190C Ambient: 30.990C
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