IRDC3891 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 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 = +12V • Fs = 600kHz • Vout1 = +1.5V @ 4A Vout2 = +3.3V @ 4A • L1 = 2.2uH L2 = 3.3uH • Cout1=4x22uF (ceramic 0805) Cout2=4x22uF (ceramic 0805) • Cin= 4x10uF (ceramic 1206) + 1x330uF (electrolytic) 07-19-2011 Confidential 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 IRDC3891 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum 4A load should be connected to VOUT+ and VOUT-. The connection diagram is shown in Fig. 1 and inputs and outputs of the board are listed in Table I. IR3891 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc is required, then R3 should be removed and external Vcc should be applied between Vcc+ and Vcc- pins. Vin pin (input of the LDO) and Vcc/LDO pins should be shorted together (populate R4) for external Vcc operation. The output of channel2 (Vout2) can follow the voltage at the Seq pin. For this purpose, The value of R5 and R6 can be selected to provide the desired sequencing ratio between Seq input and Vout2. For normal operation (non-sequencing) Seq pin should be left floating. Seq pin is internally pulled up to 3.3V. This revision of the device operates properly in FCCM (Forced Continuous Conduction Mode) and it should not be used in non-FFCM mode. Therefore EN1 and EN2 should be connected to a voltage greater than 4V. Table I. Connections Connection Signal Name VIN+ PVin (+12V) VIN- Ground of PVin VOUT1+ Vout1 (+1.5V) VOUT1- Ground of Vout1 VOUT2+ Vout2 (+3.3V) VOUT2- Ground of Vout2 VCC+ VCC/LDO pin VCC- Connected to PGND VSEQ Sequence input EN1, EN2 Enable input of each channel Sync Synchronous input LAYOUT The PCB is a 4-layer board. All of layers are 2 Oz. copper. The IR3891 and other components are mounted on the top and bottom side of the board. Power supply decoupling capacitors, the Bootstrap capacitor and feedback components are located close to IR3891. The feedback resistors are connected to the output voltage at the point of regulation and are located close to IR3891. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. 07-19-2011 Confidential 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 Connection Diagram V OUT1 V OUT2 GROUND GROUND PGood1 Sync PGood1 SEQ Vsns1 Vsns2 EN1 EN2 Vcc/LDO_out Vin GROUND Fig. 1: Connection diagram of IR3891 evaluation board (top and bottom) 07-19-2011 Confidential 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 R50 is the Single point connection between AGND and PGND. Fig. 2: Board layout, top layer Fig. 3: Board layout, bottom layer 07-19-2011 Confidential 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 Fig. 4: Board layout, mid-layer I Fig. 5: Board layout, mid-layer II 07-19-2011 Confidential 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 J111 JUMPER1 J211 JUMPER1 Vin- 1 1 + C1 N/S N/S Vin Vcc- N/S R29 N/S R28 R211 7.5k 7.5k N/S R19 N/S C212 10uF Vcc+ N/S C29 EN/FCCM2 VCC N/S C19 EN/FCCM1 C113 C213 R18 R111 330uF/25V VSeq N/S C7 C211 10uF C112 R5 0 N/S R6 2.2uF C8 10uF R4 0 R3 N/S N/S C9 C6 1.0uF C111 10uF 1 SY NC 6 5 4 3 2 1 PGood1 Confidential 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. C12 100pF R11 4.99k C11 4.7nF IR3891 Vsns2 N/S C27 C22 100pF R27 1K 5.62K N/S R15 20 B1 C122 22uF C123 22uF C124 22uF C125 22uF C126 N/S C127 N/S + C128 N/S A2 R25 20 B2 C222 22uF C223 22uF C224 22uF C225 22uF 0 R50 C226 N/S V1 Agnd 1 1 1 1 Vout2- Vout2- Vout2+ Vout2+ Vout1- Vout1- Vout1+ Vout1+ Agnd Agnd Agnd Agnd Agnd 1 1 C221 0.1uF Vout2 1 1 C121 0.1uF Vout1 Agnd Agnd C227 + C228 N/S V2 N/S Output ceramic: 0805 (use 1206 footprint) C23 A1 2200pF R22 R23 1K 100 R24 5.62k R26 PGood2 R2 49.9K VCC 3.3uH L2 R21 C26 SW2 5.49K C24 0.1uF 0 Vin R20 0.1uF C20 0.1uF 2.2uH C21 13 14 15 16 17 18 R12 5.36k L1 C13 2200pF 4.7nF Boot2 PVin2 PGnd2 SW2 SW1 PGnd1 C14 0.1uF C10 0 R10 SW1 R13 2.67k 95.3 R14 Fig.6: Schematic of the IR3891 evaluation board 39.2K R9 Seq GND1 Vcc/LDO Vin EN/FCCM1 Vsns1 U1 R1 49.9K VCC GND2 Vin- R17 2.67k FB1 N/S Comp1 1 1 2 1 2 Boot1 Input ceramic: 1206 1 1 1 1 22 Vsns2 PVin1 Vin+ 1 1 1 FB2 10 24 Rt/Sync 7 21 PGood1 11 23 EN/FCCM2 8 20 Comp2 19 PGood2 12 1 1 1 1 C17 1 1 1 1 1 Vin+ PGND PGND 1 R16 5.36k 1 Vin 1 1 9 1 1 1 N/S 1 C16 1 07-19-2011 1 Vsns1 IRDC3891 6 IRDC3891 Bill of Materials Vin=12V, Vout1=1.5V/4A, Vout=3.3V/4A, fs=600KHz Item Qty 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Part Reference 1 C1 4 C111 C112 C211 C212 1 C6 1 C8 C10 C14 C20 C24 C121 6 C221 2 C11 C21 2 C12 C22 2 C13 C23 C122 C123 C124 C125 C222 8 C223 C224 C225 1 L1 1 L2 2 R1 R2 5 R3 R5 R10 R20 R50 1 R9 1 R11 2 R12 R16 2 R13 R17 1 R14 2 R15 R25 1 R21 2 R22 R26 2 R23 R27 1 R24 2 R111 R211 2 J111 J211 6 R4 R6 R18 R19 R28 R29 C7 C9 C16 C17 C19 C26 C27 16 C29 C113 C126 C127 C128 C213 C226 C227 C228 1 U1 07-19-2011 Value Description 330uF 10uF 1.0uF 2.2uF SMD Electrolytic 1206, 25V, X5R, 0603, 25V, X5R, 0603, 16V, X5R, 0.1uF 4.7nF 100pF 2200pF 22uF 2.2uH 3.3uH 49.9K 0 39.2K 4.99K 5.36K 2.67K 95.3 20 5.49K 5.62K 1.0K 100 7.5K jumper N/S F size 25V 20% 10% 10% 20% Manufacturer Part Number Panasonic Panasonic Murata TDK EEV-FK1E331P ECJ3YB1E106K GRM188R61E105KA12D C1608X5R1C225M 0603, 25V, X7R, 10% Murata GRM188R71E104KA01B 0603, 50V, X7R, 10% 0603, 50V, NP0, 5% 0603, 50V, X7R, 10% Murata Murata Murata GRM188R71H472KA01B GRM1885C1H101JA01D GRM188R71H222KA01B 0805, 6.3V, X5R, 20% TDK C2012X5R0J226M SMD 7.05x6.6x4.8mm,11.2mΩ SMD 7.05x6.6x4.8mm,19.9mΩ Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W 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,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% This is a simple jumper Cyntec Cyntec Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic PCMB065T-2R2MS PCMB065T-3R3MS ERJ-3EKF4992V ERJ-3GEY0R00V ERJ-3EKF3922V ERJ-3EKF4991V ERJ-3EKF5361V ERJ-3EKF2671V ERJ-3EKF95R3V ERJ-3EKF20R0V ERJ-3EKF5491V ERJ-3EKF5621V ERJ-3EKF1001V ERJ-3EKF1000V ERJ-3EKF7501V PQFN 5x6mm IR IR3891MPBF N/S IR3891 Confidential 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 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=0-4A, Room Temperature, No Air Flow Fig. 7: Start up at 4A Load (Note 1) Ch1:Vout1, Ch2:Vout2, Ch3:Vcc/LDO, Ch4:Vin Fig. 8: Start up at 4A Load (Note 1) Ch1:Vout1, Ch2:Vout2, Ch3:PGood1, Ch4: PGood2 Fig. 9: Start up with 2.97V Prebias, 0A Load, Ch2:Vout2 Fig. 10: Start up with 1.3V Prebias, 0A Load, Ch1:Vout1 Fig. 12: Inductor node at 4A load Ch1:SW1 Fig. 11: Inductor node at 4A load Ch1:SW2 07-19-2011 Confidential 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 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=0-4A, Room Temperature, No Air Flow Fig. 14: Short circuit (Hiccup) Response Ch1:Vout1, Ch2:Vout2 , Ch4:Io2 Fig. 13: Short circuit (Hiccup) Response Ch1:Vout1, Ch2:Vout2 , Ch4:Io1 Fig. 15: Output Voltage Ripple, 4A load on each channel (Note2) Ch1: Vout, Ch2: Vout2 07-19-2011 Confidential 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 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=0-4A, Room Temperature, No Air Flow Iout1 Fig. 16: Transient Response of channel1 0A-1.6A (0-40%), Ch1:Vout1 , Ch2:Vout2, Ch4: Io1 07-19-2011 Confidential 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 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=0-4A, Room Temperature, No Air Flow Fig. 17: Transient Response of channel2 0A-1.6A (0-40%), Ch1:Vout1 , Ch2:Vout2, Ch4: Io2 Note1: Enable is tied to Vin via a resistor divider. Note2: Vo ripple signal is taken across C111 and C221 capacitors. 07-19-2011 Confidential 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 IRDC3891 Bode Plot, Channel1 Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=4A, Room Temperature, No Air Flow Fig.18: Bode Plot of CH1 at 4A load shows a bandwidth of 97.83kHz and phase margin of 53.68 degrees 07-19-2011 Confidential 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. 12 IRDC3891 Bode Plot, Channel2 Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=4A, Room Temperature, No Air Flow Fig.19: Bode Plot of CH2 at 4A load shows a bandwidth of 97.17kHz and phase margin of 51.91 degrees 07-19-2011 Confidential 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. 13 IRDC3891 Efficiency and Power Loss of channel1 Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2 is disabled (EN2=low), Io1= 0-4A, Room Temperature, No Air Flow 90 88 Efficiency [%] 86 84 82 80 78 76 74 72 70 0.0 0.5 1.0 1.5 2.0 Io [A] 2.5 3.0 3.5 4.0 0.5 1.0 1.5 2.0 Io [A] 2.5 3.0 3.5 4.0 1.0 0.9 Power Loss [W] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.0 Fig.20: Efficiency and power loss vs. load current for channel1 (Vout1 = 1.5V) 07-19-2011 Confidential 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. 14 IRDC3891 Efficiency [%] Efficiency and Power Loss of channel2 Vin=12.0V, Vcc/LDO=5.3V, Vout1 is disabled (EN1=low), Vout2=3.3V, Io2=0-4A, Room Temperature, No Air Flow 96 94 92 90 88 86 84 82 80 78 76 74 72 70 Power Loss [W] 0.0 0.5 1.0 1.5 2.0 Io [A] 2.5 3.0 3.5 4.0 0.5 1.0 1.5 2.0 Io [A] 2.5 3.0 3.5 4.0 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.0 Fig.21: Efficiency and power loss vs. load current for channel2 (Vout2 = 3.3V) 07-19-2011 Confidential 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. 15 IRDC3891 Thermal Image Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.5V, Vout2=3.3V, Io1= Io2=4A, Room Temperature, No Air Flow Fig.22: Thermal Image at Io1=Io2=4A load Test Point 1: IR3891, Test Point 2: Inductor_Ch1, Test Point 3: Inductor_Ch2 07-19-2011 Confidential 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. 16 IRDC3891 IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 7/11 07-19-2011 Confidential 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.