IRDC3891 SupIRBuck TM USER GUIDE FOR IR3891 EVALUATION BOARD DESCRIPTION The IR3899 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 = +1.8V @ 0-4A Vout2 = +1.2V @ 0-4A • L1 = 2.2uH L2 = 1.5uH • 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 (+1.8V) VOUT1- Ground of Vout1 VOUT2+ Vout2 (+1.2V) 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 SEQ 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 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. Vin- 1 1 49.9K R28 Vin C4 10nF VSeq N/S C7 N/S C29 EN/FCCM2 R5 0 2.2uF C8 N/S C2 10uF N/S R6 VCC 10uF C3 R4 N/S C19 EN/FCCM1 33.3K R29 Vcc+ 33.3K R19 Vcc- 49.9K R18 330uF/25V 1 Vin- C5 10nF 1 + C1 R3 0 N/S C9 C6 1.0uF SY NC 39.2K R9 Seq GND1 Vcc/LDO Vin EN/FCCM1 Vsns1 R11 3.24k C12 150pF C11 10nF IR3891 Vsns2 19 R21 2.87K C21 NS C27 C22 150pF 0 R27 2.87K 4.02k R26 Vin 0.1uF C10 0.1uF C20 R20 C24 0.1uF 13 14 15 16 17 18 10nF Boot2 PVin2 PGnd2 SW2 SW1 PGnd1 C14 0.1uF R10 0 R2 49.9K VCC PGood2 R12 C23 A1 4.02k R22 2200pF 1.5uH R23 2.87K 130 R24 2.2uH L2 C13 2200pF 4.02k L1 R13 1.54K 130 R14 A2 1 1 J2 N/S 20 R25 N/S J1 R15 20 Fig.6: Schematic of the IR3891 evaluation board 6 5 4 3 2 1 U1 R1 49.9K VCC PGood1 1 1 1 22 Input ceramic: 1206, 25V 1 1 Rt/Sync 7 EN/FCCM2 1 1 24 GND2 23 FB1 9 FB2 10 Vsns2 1 8 Comp1 20 Boot1 21 PGood1 Comp2 11 PVin1 PGood2 12 Vin+ 1 2 2 B1 1 B2 1 1 1 R17 1.54K 0 R50 C222 N/S C223 N/S C112 C113 NS NS 1 Vout1=1.8V 1 1 C221 0.1uF 1 1 Vout2- Vout2- Vout2+ Agnd Agnd Agnd Agnd Agnd C227 22uF Vout1- Vout2=1.2V 1 Vout2+ Vout1+ Vout1+ 0.1uF Vout11 1 C116 C117 22uF 22uF C111 C225 C226 22uF 22uF C115 22uF Agnd Agnd Agnd C224 22uF C114 22uF 1 NS 1 C17 1 1 1 Vin+ 1 R16 4.02k 1 Vin 1 07-19-2011 1 Vsns1 IRDC3891 6 IRDC3891 Bill of Materials Item Qty 1 Value Description 1 C1 Part Reference 330uF/25V SMD Electrolytic F size 25V 20% Panasonic Manufacturer Part Number EEV-FK1E331P 2 4 C2 C3 C4 C5 10uF 1206, 25V, X5R, +/-10% Panasonic ECJ3YB1E106K 3 1 C6 1.0uF 0603, 25V, X5R, 10% Murata GRM188R61E105KA12D 4 1 C8 2.2uF 0603, 16V, X5R, 20% TDK C1608X5R1C225M 5 C10 C14 C20 C24 C111 6 C221 0.1uF 0603, 25V, X7R, 10% Murata GRM188R71E104KA01D 6 2 C11 C21 10nF 0603,50V,X7R Murata GRM188R71H103KA01D 7 1 C22 150pF 0603, 50V, NP0, 5% Murata GRM1885C1H151JA01D 8 1 C12 150pF 0603, 50V, NP0, 5% Murata GRM1885C1H151JA01D 9 2 C13 C23 2200pF 0603,50V,X7R Murata GRM188R71H222KA01D 10 C114 C115 C116 C117 C224 8 C225 C226 C227 22uF 11 1 L1 2.2uH SMD 7.05x6.6x4.8mm,11.2mΩ 12 1 L2 1.5uH SMD 7.05x6.6x4.8mm,6.7mΩ Cyntec PCMB065T-1R5MS 13 4 R1 R2 R18 R28 49.9K Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF4992V 0805, 6.3V, X5R, 20% TDK C2012X5R0J226M Cyntec PCMB065T-2R2MS 14 5 R3 R5 R10 R20 R50 0 Thick Film, 0603,1/10W Panasonic ERJ-3GEY0R00V 15 1 R9 39.2K Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF3922V 16 1 R11 3.24k Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF3241V 17 1 R21 2.87K Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF2871V 18 4 R12 R16 R22 R26 4.02k Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF4021V 19 2 R14 R24 130 Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF1300V 20 2 R13 R17 1.54K Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF1541V 21 2 R23 R27 2.87K Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF2871V 22 2 R15 R25 20 Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF20R0V Panasonic ERJ-3EKF3322V IR IR3891MPBF 23 2 R19 R29 33.2k Thick Film, 0603,1/10W,1% 24 1 U1 IR3891 PQFN 5x6mm 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. 7 IRDC3891 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, 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 0.1.08V Prebias, 0A Load, Ch2:Vout2 Fig. 10: Start up with 1.62V 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=1.8V, Vout2=1.2V, Io1= Io2=0-4A, Room Temperature, No Air Flow Fig. 13: Short circuit (Hiccup) Response Ch1:Vout1, Ch2:Vout2 , Ch4:Io1 Fig. 14: Short circuit (Hiccup) Response Ch1:Vout1, Ch2:Vout2 , Ch4:Io2 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=1.8V, Vout2=1.2V, Io1= Io2=0-4A, Room Temperature, No Air Flow 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=1.8V, Vout2=1.2V, 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 C113 and C223 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=1.8V, Vout2=1.2V, Io1= Io2=4A, Room Temperature, No Air Flow Fig.18: Bode Plot of CH1 at 4A load shows a bandwidth of 94.6kHz and phase margin of 51.4 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=1.8V, Vout2=1.2V, Io1= Io2=4A, Room Temperature, No Air Flow Fig.19: Bode Plot of CH2 at 4A load shows a bandwidth of 105kHz and phase margin of 50.7 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=1.8V, Vout2 is disabled (EN2=low), Io1= 0-4A, Room Temperature, No Air Flow 92 90 88 Efficiency [%] 86 84 82 80 78 76 74 72 70 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 2.25 2.5 2.75 3 3.25 3.5 3.75 4 Io [A] 0.9 Power Loss [W] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 Io [A] Fig.20: Efficiency and power loss vs. load current for channel1 (Vout1 = 1.8V) 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 and Power Loss of channel2 Vin=12.0V, Vcc/LDO=5.3V, Vout1 is disabled (EN1=low), Vout2=1.2V, Io2=0-4A, Room Temperature, No Air Flow 88 86 Efficiency [%] 84 82 80 78 76 74 72 70 68 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 2.25 2.5 2.75 3 3.25 3.5 3.75 4 Io [A] 0.9 Power Loss [W] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 Io [A] Fig.21: Efficiency and power loss vs. load current for channel2 (Vout2 = 1.2V) 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=1.8V, Vout2=1.2V, 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.