IRDC3891

IRDC3891 SupIRBuck TM USER GUIDE FOR IRDC3891 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 IRDC3891 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 = 600kHz • Vout1 = +1.8V @ 4A Vout2 = +1.2V @ 4A • L1 = 2.2uH L2 = 1.5uH • Cout1=4x22uF (ceramic 0805) Cout2=4x22uF (ceramic 0805) • Cin= 4x10uF (ceramic 1206) + 1x330uF (electrolytic) 04-30-2013 1 AL 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. 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. 04-30-2013 2 AL IRDC3891 Connection Diagram V OUT1 V OUT2 GROUND GROUND PGood1 SEQ PGood2 Sync Vsns1 EN1 Vsns2 EN2 VPG Vcc/LDO_out Vin GROUND Fig. 1: Connection diagram of IRDC3891 evaluation board (top and bottom) 04-30-2013 3 AL IRDC3891 R50 is the Single point connection between AGND and PGND. Fig. 2: Board layout, top layer Fig. 3: Board layout, bottom layer 04-30-2013 4 AL IRDC3891 Fig. 4: Board layout, mid-layer I Fig. 5: Board layout, mid-layer II 04-30-2013 5 AL Vin- Vin- Vin- 1 1 1 JUMPER1 J211 JUMPER1 J111 Vin 11.8k R29 84.5K R28 N/S VSeq EN2 N/S C29 DIODE SY NC D1 0 R5 2.2uF C8 10uF C112 R6 N/S N/S C7 10uF 10uF C19 C211 C212 VCC Vcc+ Vcc- 11.8k R19 N/S N/S EN1 C113 C213 R211 N/S N/S R111 84.5K 330uF/25V R18 + C1 Input ceramic: 1206 39.2K R9 N/S C9 C6 1.0uF 10uF C111 N/S R4 0 R3 Vsns2 9 8 7 6 5 4 3 2 1 R11 3.24k 10nF C11 Vsns2 EN2 Rt/Sy nc Seq GND Vcc/LDO Vin EN1 Vsns1 U1 150pF C12 Vpg R1 R7 49.9K N/S VCC PGood1 1 29 1 1 2 1 2 1 IR3891 25 Vin+ 2.87K 10nF C22 150pF R21 C21 0.1uF C24 0 R10 C14 0.1uF NS C27 Vin 0 R20 19 20 21 R27 2.87K Vpg 0.1uF C20 R26 4.02k C26 NS SW2 SW2 SW1 SW1 22 0.1uF C10 R12 SW1 SW2 R23 2.87K 130 R24 2.2uH L1 20 R15 B1 C123 22uF C122 22uF 22uF C124 22uF C125 N/S C126 N/S C127 2200pF C23 1.5uH L2 A2 20 R25 B2 C223 22uF C222 22uF 22uF C224 22uF C225 0 R50 N/S C226 N/S 1 1 1 1 1 1 C221 0.1uF 1 1 Vout2 1 1 1 1 C121 0.1uF Vout1 Vout2- Vout2- Vout2- Vout2+ Vout2+ Vout2+ Vout1- Vout1- Vout1- Vout1+ Vout1+ Vout1+ Agnd Agnd Agnd Agnd Agnd V2 V1 Agnd Agnd N/S PGND PGND PGND Agnd N/S C227 N/S C129 C228 C229 N/S C128 Output ceramic: 0805 (use 1206 footprint) R22 A1 4.02k SW11 SW22 PGood2 R2 49.9K VCC R8 N/S Vpg C13 2200pF 4.02k R13 1.54k 130 1 R14 1 Fig.6: Schematic of the IRDC3891 evaluation board 10 1 1 31 FB1 FB2 30 Comp1 11 PGood1 Comp2 28 Boot2 13 PVin2 14 1 1 1 15 PGood2 12 Boot1 27 PVin1 26 PVin1 PVin2 24 PGND1 16 PGND1 PGND2 23 PGND1 PGND2 17 PGND2 18 4.02k 1 1 1 1 1 1 Vin+ NS 1 1 1 R16 1 R17 1.54k 1 C17 1 Vin 1 1 1 1 1 1 1 1 Vin+ 1 C16 NS 1 04-30-2013 1 Vsns1 IRDC3891 6 AL IRDC3891 Bill of Materials Item Qty 1 1 2 4 3 1 4 1 5 6 6 7 8 9 10 1 1 2 1 1 11 8 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 1 1 2 5 1 1 2 2 1 2 2 2 1 2 2 1 2 1 30 1 Vin=12.0V, Vout1=1.8V/4A, Vout2=1.2V/4A, Fsw=600KHz Part Reference Value Description Manufacturer C1 330uF SMD Electrolytic F size 25V 20% Panasonic 1206, 25V, X5R, 10% C111 C112 C211 C212 10uF TDK 0603, 25V, X5R, 10% C6 1.0uF Murata 0603, 16V, X5R, 20% C8 2.2uF TDK C10 C14 C20 C24 C121 0.1uF 0603, 25V, X7R, 10% Murata C221 C11 10nF 0603, 50V, X7R, 10% Murata 0603, 50V, NP0, 5% Murata C12 150pF C13 C23 2200pF 0603, 50V, X7R, 10% Murata C21 10nF 0603, 50V, X7R, 10% Murata 0603, 50V, NP0, 5% Murata C22 150pF C122 C123 C124 C125 0805, 6.3V, X5R, 20% 22uF TDK C222 C223 C224 C225 L1 2.2uH SMD 7.05x6.6x4.8mm,11.2mΩ Cyntec L2 1.5uH SMD 7.05x6.6x4.8mm,6.0mΩ Cyntec Thick Film, 0603,1/10W,1% R1 R2 49.9K Panasonic Thick Film, 0603,1/10W R3 R5 R10 R20 R50 0 Panasonic Thick Film, 0603,1/10W,1% R9 39.2K Panasonic Thick Film, 0603,1/10W,1% R11 3.24K Panasonic Thick Film, 0603,1/10W,1% R12 R16 4.02K Panasonic Thick Film, 0603,1/10W,1% R13 R17 1.54K Panasonic Thick Film, 0603,1/10W,1% R14 130 Panasonic Thick Film, 0603,1/10W,1% R15 R25 20 Panasonic Thick Film, 0603,1/10W,1% R18 R28 84.5K Panasonic Thick Film, 0603,1/10W,1% R19 R29 11.8K Panasonic Thick Film, 0603,1/10W,1% R21 2.87K Panasonic Thick Film, 0603,1/10W,1% R22 R26 4.02K Panasonic Thick Film, 0603,1/10W,1% R23 R27 2.87K Panasonic Thick Film, 0603,1/10W,1% R24 130 Panasonic This is a simple jumper J111 J211 jumper D1 Schottky, 40V, SOD-523 Vishay International U1 IR3891 PQFN 5x6mm Rectifier 04-30-2013 Part Number EEV-FK1E331P C3216X5R1E106K GRM188R61E105KA12D C1608X5R1C225M GRM188R71E104KA01B GRM188R71H103KA01B GRM1885C1H151JA01D GRM188R71H222KA01B GRM188R71H103KA01B GRM1885C1H151JA01D C2012X5R0J226M PCMB065T-2R2MS PCMB065T-1R5MS ERJ-3EKF4992V ERJ-3GEY0R00V ERJ-3EKF3922V ERJ-3EKF3241V ERJ-3EKF4021V ERJ-3EKF1541V ERJ-3EKF1300V ERJ-3EKF20R0V ERJ-3EKF8452V ERJ-3EKF1182V ERJ-3EKF2871V ERJ-3EKF4021V ERJ-3EKF2871V ERJ-3EKF1300V BAS40-02VGS08 IR3891MPBF 7 AL 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 1.05V Prebias, 0A Load Ch1:Enable2, Ch2:Vout2, Ch4:PGood2 Fig. 10: Start up with 1.52V Prebias, 0A Load Ch1:Enable1 , Ch2:Vout1, Ch4:PGood1 Fig. 11: Inductor switch node at 4A load / Channel Ch1:SW1, Ch2:SW2 Fig. 12: Output Voltage Ripple, 4A load/channel (Note2) Ch1: Vout1, Ch2: Vout2 04-30-2013 8 AL IRDC3891 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Room Temperature, No air flow Fig. 15: Transient Response of channel1 0A-1.6A (0-40%), Ch1:Vout1 , Ch2:Vout2, Ch4: Iout1 04-30-2013 9 AL IRDC3891 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Room Temperature, No air flow Fig. 16: Transient Response of channel2 0A-1.6A (0-40%), Ch1:Vout1 , Ch2:Vout2, Ch4: Iout2 Note1: Enable is tied to Vin via a resistor divider. Note2: Vo ripple signal is taken across C125 and C225 capacitors. 04-30-2013 10 AL 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.17: Bode Plot of CH1 at 4A load: Fo = 84.85 kHz; Phase Margin = 51.88º 04-30-2013 11 AL 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.18: Bode Plot of CH2 at 4A load: Fo = 113.06 kHz; Phase Margin = 48.19º 04-30-2013 12 AL IRDC3891 Efficiency [%] 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 94 92 90 88 86 84 82 80 78 76 74 72 70 68 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.19: Efficiency and power loss vs. load current for channel1 (Vout1 = 1.8V) 04-30-2013 13 AL IRDC3891 Efficiency [%] 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 94 92 90 88 86 84 82 80 78 76 74 72 70 68 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 channel2 (Vout2 = 1.2V) 04-30-2013 14 AL 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.21: Thermal Image at Io1=Io2=4A load Test Point 1: IR3891, Test Point 2: Inductor_Ch1, Test Point 3: Inductor_Ch2 04-30-2013 15 AL 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. 04-30-2013 16 AL