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 = +12.0V • Fs = 900kHz • Vout1 = +3.3V @ 1A Vout2 = +2.5V @ 1A • L1 = 3.3uH L2 = 3.3uH • Cout1=1x22uF (ceramic 0805) Cout2=1x22uF (ceramic 0805) • Cin= 2x10uF (ceramic 1206) + 1x330uF (electrolytic) 02-14-2012 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 +12.0V 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 (+3.3V) VOUT1- Ground of Vout1 VOUT2+ Vout2 (+2.5V) 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. 02-14-2012 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) 02-14-2012 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 02-14-2012 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 02-14-2012 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 Vin Vcc- 11.8K R29 84.5K R28 R211 N/S N/S 11.8K R19 C212 N/S Vcc+ N/S C29 EN/FCCM2 VCC N/S C19 EN/FCCM1 N/S N/S R18 C113 C213 84.5K R111 330uF/25V JUMPER1 Vin- 1 1 + C1 VSeq N/S C7 C211 10uF R5 0 N/S R6 2.2uF C8 N/S C112 Input ceramic: 1206 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 160pF R11 2.1k C11 6.8nF IR3891 Vsns2 N/S C27 C22 160pF R27 1.37K 5.49K N/S R15 20 B1 C122 22uF C123 N/S C124 N/S C125 N/S C126 N/S C127 N/S + C128 N/S A2 R25 20 B2 C222 22uF C223 N/S C224 N/S C225 N/S 0 R50 C226 N/S V1 1 1 Agnd Agnd 1 1 Vout2- Vout2- Vout2+ Vout2+ Vout1- Vout1- Vout1+ Vout1+ Vo2: 2.5V Vo1: 3.3V Agnd Agnd Agnd Agnd Agnd 1 1 C221 0.1uF Vout2 1 1 C121 0.1uF Vout1 Agnd C227 + C228 N/S V2 N/S Output ceramic: 0805 (use 1206 footprint) C23 A1 2200pF R22 R23 1.37K 42.2 R24 3.3uH L2 5.49k R26 PGood2 R2 49.9K VCC R21 C26 SW2 2.37K C24 0.1uF 0 Vin R20 0.1uF C20 0.1uF 3.3uH C21 13 14 15 16 17 18 R12 3.57k L1 C13 2200pF 10nF Boot2 PVin2 PGnd2 SW2 SW1 PGnd1 C14 0.1uF C10 0 R10 SW1 R13 634 63.4 R14 Fig.6: Schematic of the IR3891 evaluation board 26.1K R9 Seq GND1 Vcc/LDO Vin EN/FCCM1 Vsns1 U1 R1 49.9K VCC R17 634 GND2 N/S FB1 C17 Comp1 Vin- 1 2 1 2 Boot1 1 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 1 1 1 1 Vin+ 1 R16 3.57k 1 PGND PGND 1 1 9 1 1 1 Vin 1 N/S 1 C16 1 02-14-2012 1 Vsns1 IRDC3891 6 IRDC3891 Bill of Materials Vin=12.0V, Vout1=3.3V/1A, Vout2=2.5V/1A, fs=900KHz Item 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 29 30 31 32 Qty Part Reference 1 C1 2 C111 C211 1 C6 1 C8 6 C10 C14 C20 C24 C121 C221 1 C11 1 C12 2 C13 C23 1 C21 1 C22 2 C122 C222 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 2 R18 R28 2 R19 R29 1 R21 2 R22 R26 2 R23 R27 1 R24 2 R111 R211 2 J111 J211 2 R4 R6 C7 C9 C16 C17 C19 C26 C27 C29 C112 C113 C123 C124 24 C125 C126 C127 C128 C212 C213 C223 C224 C225 C226 C227 C228 1 U1 02-14-2012 Value 330uF 10uF 1.0uF 2.2uF 0.1uF 6.8nF 160pF 2200pF 10nF 160pF 22uF 3.3uH 3.3uH 49.9K 0 26.1K 2.1K 3.57K 634 63.4 20 84.5K 11.8K 2.37K 5.49K 1.37K 42.2 N/S jumper N/S Description SMD Electrolytic F size 25V 20% 1206, 25V, X5R, 10% 0603, 25V, X5R, 10% 0603, 16V, X5R, 20% 0603, 25V, X7R, 10% 0603, 50V, X7R, 10% 0603, 50V, NP0, 5% 0603, 50V, X7R, 10% 0603, 50V, X7R, 10% 0603, 50V, NP0, 5% 0805, 10V, X5R, 20% SMD 4.85x4.7x2.8mm,32mΩ SMD 4.85x4.7x2.8mm,32mΩ 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% Thick Film, 0603,1/10W,1% Manufacturer Part Number Panasonic TDK Murata TDK Murata Murata Murata Murata Murata Murata TDK Cyntec Cyntec Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic EEV-FK1E331P C3216X5R1E106K GRM188R61E105KA12D C1608X5R1C225M GRM188R71E104KA01B GRM188R71H682KA01B GRM1885C1H161JA01D GRM188R71H222KA01B GRM188R71H103KA01B GRM1885C1H161JA01D C2012X5R1A226M PCMB065T-3R3MS PCMB065T-3R3MS ERJ-3EKF4992V ERJ-3GEY0R00V ERJ-3EKF2612V ERJ-3EKF2101V ERJ-3EKF3571V ERJ-3EKF6340V ERJ-3EKF63R4V ERJ-3EKF20R0V ERJ-3EKF8452V ERJ-3EKF1182V ERJ-3EKF2371V ERJ-3EKF5491V ERJ-3EKF1371V ERJ-3EKF42R2V IR IR3891MPBF This is a simple jumper N/S IR3891 PQFN 5x6mm 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=3.3V, Vout2=2.5V, Io1= Io2=0-1A, Room Temperature, No Air Flow Fig. 7: Start up at 1A Load (Note 1) Ch1:Vout1, Ch2:Vout2, Ch3:Vcc/LDO, Ch4:Vin Fig. 8: Start up at 1A Load (Note 1) Ch1:Vout1, Ch2:Vout2, Ch3:PGood1, Ch4: PGood2 Fig. 9: Start up with 2.125V Prebias, 0A Load, Ch2:Vout2 Fig. 10: Start up with 2.805V Prebias, 0A Load, Ch1:Vout1 Fig. 12: Inductor node at 1A load Ch1:SW1 Fig. 11: Inductor node at 1A load Ch1:SW2 02-14-2012 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=3.3V, Vout2=2.5V, Io1= Io2=0-1A, 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, 1A load on each channel (Note2) Ch1: Vout, Ch2: Vout2 02-14-2012 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=3.3V, Vout2=2.5V, Io1= Io2=0-1A, Room Temperature, No Air Flow Fig. 16: Transient Response of channel1 0A-0.5A (0-50%), Ch1:Vout1 , Ch2:Vout2, Ch4: Io1 02-14-2012 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=3.3V, Vout2=2.5V, Io1= Io2=0-1A, Room Temperature, No Air Flow Fig. 17: Transient Response of channel2 0A-0.5A (0-50%), Ch1:Vout1 , Ch2:Vout2, Ch4: Io2 Note1: Enable is tied to Vin via a resistor divider. Note2: Vo ripple signal is taken across C122 and C222 capacitors. 02-14-2012 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=3.3V, Vout2=2.5V, Io1= Io2=1A, Room Temperature, No Air Flow Fig.18: Bode Plot of CH1 at 1A load shows a bandwidth of 153.94 kHz and phase margin of 53.59 degrees 02-14-2012 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=3.3V, Vout2=2.5V, Io1= Io2=1A, Room Temperature, No Air Flow Fig.19: Bode Plot of CH2 at 1A load shows a bandwidth of 145.91 kHz and phase margin of 60.31 degrees 02-14-2012 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 [%] Efficiency and Power Loss of channel1 Vin=12.0V, Vcc/LDO=5.3V, Vout1=3.3V, Vout2 is disabled (EN2=low), Io1= 0-2A, Room Temperature, No Air Flow 94 92 90 88 86 84 82 80 78 76 74 72 70 0 0.25 0.5 0.75 1 Io [A] 1.25 1.5 1.75 2 0 0.25 0.5 0.75 1 Io [A] 1.25 1.5 1.75 2 1 0.9 Power Loss [W] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Fig.20: Efficiency and power loss vs. load current for channel1 (Vout1 = 3.3V) 02-14-2012 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=2.5V, Io2=0-2A, Room Temperature, No Air Flow 94 92 90 88 86 84 82 80 78 76 74 72 70 0 0.25 0.5 0.75 1 Io [A] 1.25 1.5 1.75 2 0 0.25 0.5 0.75 1 Io [A] 1.25 1.5 1.75 2 1 0.9 Power Loss [W] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Fig.21: Efficiency and power loss vs. load current for channel2 (Vout2 = 2.5V) 02-14-2012 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=3.3V, Vout2=2.5V, Io1= Io2=1A, Room Temperature, No Air Flow Fig.22: Thermal Image at Io1=Io2=1A load Test Point 1: IR3891, Test Point 2: Inductor_Ch1, Test Point 3: Inductor_Ch2 02-14-2012 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. 10/11 02-14-2012 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.