IRDC3891-P1V2 SupIRBuck TM USER GUIDE FOR IR3891 EVALUATION BOARD DESCRIPTION The IR3891 is a dual synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mm X 6mm Power QFN package. Key features offered by the IR3891 include internal Digital Soft Start, precision 0.5V reference 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, internal LDO, pre-bias start-up, output over voltage protection as well as open feedback line protection. 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 IR3891 15mmx11mm evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3891 is available in the IR3891 data sheet. BOARD FEATURES • Vin = +12.0V • Fs = 450kHz • Vout1 = +1.2V @ 3A Vout2 = +1.2V @ 3A • L1 = 2.2uH L2 = 2.2uH • Cout1=1x22uF (ceramic 1206) Cout2=1x22uF (ceramic 1206) • Cin= 2x10uF (ceramic 1206) 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 1 MC IRDC3891-P1V2 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and GND. A maximum of 3A load should be connected to Vo+ and GND. The inputs and output connections of the board are listed in Table I. Table I. Connections Connection Signal Name VIN+ Vin (+12V) Vo1+ Vout1(+1.2V) Vo2+ Vout2(+1.2V) Gnd Power Ground En1 Enable 1 En2 Enable 2 Trim1 Vout adjustment for channel 1 Trim2 Vout adjustment for channel 2 LAYOUT The PCB is a compact 15mmx11mm, 4-layer board using FR4 material. All layers use 2 Oz. copper. The PCB thickness is 0.062”. Power supply decoupling capacitors, the bootstrap capacitor and feedback components are located close to IR3891. 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. 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 2 IRDC3891-P1V2 Connection Diagram 15mm 11mm Top View Vo1 Gnd Vin Vin Gnd Vo2 Bottom View Trim2 En2 En1 Trim1 Fig. 1: Connection Diagram of IR3891 Evaluation Boards 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 3 IRDC3891-P1V2 11mm Vin Gnd Vo Trim Vin En Gnd En Vo Trim 15mm Fig. 2: Board Layout-Top Layer Single point connection between AGnd and PGnd Fig. 3: Board Layout-Bottom Layer 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 4 IRDC3891-P1V2 Fig. 4: Board Layout-Mid Layer 1 Fig. 5: Board Layout-Mid Layer 2 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 5 53.6K R9 C8 R4 7.5k 49.9K R3 Vin 1 2.2uF EN2 C6 1.0uF 49.9K R5 EN1 R6 7.5k 1 C11 10nF 9 8 7 6 5 4 3 2 1 Vsns2 EN2 Rt/Sy nc Seq GND Vcc/LDO Vin EN1 Vsns1 U1 1.5k 470pF R11 C12 25 IR3891 Vin 23 C22 470pF R21 1.5k C21 19 20 21 22 10nF SW2 SW2 SW1 SW1 0.1uF C10 R16 N/S Trim1 1 24 Trim2 R26 N/S 0.1uF C20 R13 4.02k 210 L1 10 C23 R25 10 R22 5.62k 2200pF 22uF C222 22uF C122 GND VOUT2 VOUT1 GND CON6 J1 6 5 4 3 2 1 VIN Single Point Connection between AGND and PGND R23 4.02k 210 R24 2.2uH, IHLP-2020-CZ-A1 L2 2.2uH, IHLP-2020-CZ-01 R15 R12 C13 5.62k 2200pF Fig. 6: Schematic of the IR3891 evaluation board Vin=12V, Vo=1.2V, fsw=450kHz, Iomax=3A 10uF C111 10uF 31 FB1 29 PGood1 30 11 FB2 10 Comp1 Comp2 28 Boot2 13 PVin2 14 PGood2 12 Boot1 27 PVin1 26 PVin1 PVin2 15 PGND1 PGND2 16 PGND1 PGND2 17 PGND1 PGND2 C112 1 04-08-2013 18 Vin R14 IRDC3891-P1V2 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 6 IRDC3891-P1V2 Bill of Materials Item Qty Part Reference Value Description Manufacturer Part Number 1 2 C112, C111 10uF 1206, 25V, X5R, 20% TDK C3216X5R1E106M 2 2 C13, C23 2200pF 0402, 50V, X5R, 10% TDK C1005X5R1H222K050BA 3 2 C10, C20 0.1uF 0402, 50V, X5R, 10% TDK C1005X5R1H104K050BB 4 2 C11, C21 10nF 0402, 25V, X5R, 10% TDK C1005X5R1E103K050BA 5 2 C12, C22 470pF 0402, 50V, X5R, 10% TDK C1005X5R1H471K050BA 6 1 C6 1.0uF 0402, 16V, X5R, 10% TDK C1005X5R1C105K050BC 7 1 C8 2.2uF 0402, 10V, X5R, 10% TDK C1005X5R1A225K050BC 8 2 C122, C222 22uF 1206, 10V, X5R, 20% TDK C3216X5R1A226M160AC 9 2 R15, R25 10Ω Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF10R0X 10 2 R14, R24 210Ω Thick film, 0402, 1/10W, 1% Panasonic 11 2 R12, R22 5.62kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF5621X 12 2 R13, R23 4.02kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF4021X 13 2 R11, R21 1.5kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF1501X 14 2 R5, R3 49.9kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF4992X 15 2 R4, R6 7.5kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF7501X 16 1 R9 53.6kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF5362X 17 1 L1, L2 2.2uH 5.49mm x 5.18mm, DCR=27.8mΩ Vishay IHLP-2020CZ-A1 2.2uH 18 1 U1 IR3891 5mm x 6 mm QFN IR IR3891MTR1PBF 04-08-2013 ERJ-2RKF2100X Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 7 IRDC3891-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-4A, Room Temperature, no airflow Fig. 8: Start up with 1V Pre Bias, 0A Load, Ch2:Vo Fig. 7: Start up at 3A Load, Ch2:Vo Fig. 10: Output Voltage Ripple, 3A load Ch3: Vout , Fig. 9: Transient Response, 1.5A to 3A step Ch2:Vout Ch4-Iout Fig. 11: Inductor node at 3A load, Ch2:LX, Due to the limit of board size, the reference of the probe is connected to GND terminal of Cout. Thus, the negative spike is high. 04-08-2013 Fig. 12: Short circuit (Hiccup) Recovery, Ch2:Vout , Ch4:Iout Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 8 IRDC3891-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-3A, Room Temperature, no air flow Fig. 14: Bode Plot at 3A load shows a bandwidth of 87kHz and phase margin of 50 degrees and gain margin of -10dB Fig. 14: Bode Plot at 3A load with one additional 47uF/10V/1210 output capacitors. Bandwidth is 35.6kHz and phase margin of 47.8 degrees and gain margin of -24dB. 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 9 IRDC3891-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-3A, Room Temperature, no air flow Fig.16 : Efficiency versus load current Fig.17: Power loss versus load current 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 10 IRDC3891-P1V2 THERMAL IMAGES Vin=12.0V, Vo=1.2V, Io=3A, Room Temperature, No Air flow Fig. 19: Thermal Image of the board at 3A load of both phases. Test point is IR3891 Temperature = 82ºC. For easy test, Vin, GND and Vout1 and Vout2 of IR3891 demo board are connected to another PCB through the copper leads. There copper leads help remove the heat from the IR3891demo board. Using large copper area on the other PCB will further help reduce the temperature of IR3891 demo board. 04-08-2013 Preliminary This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice 11