IRDC3846-P1V2 SupIRBuck TM USER GUIDE FOR IRDC3846 EVALUATION BOARD DESCRIPTION The IR3846 is a synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mmx7mm QFN package. Key features offered by the IR3846 include internal Digital Soft Start, precision 0.6V 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, true differential remote sensing and pre-bias start-up. A thermally compensated 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. This user guide contains the schematic and bill of materials for the IRDC3846 evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3846 is available in the IR3846 data sheet. BOARD FEATURES • Vin = +12V, No Vcc required. • Vout = +1.2V @ 0-35A • Fs=600kHz • L= 0.250uH • Cin= 7x22uF (ceramic 1206) + 1x330uF (electrolytic) • Cout= 6x100uF (ceramic 1206) 9/11/2013 1 AL IRDC3846-P1V2 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 35A load should be connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I. IR3846 needs 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 can be applied between Vcc+ and Vcc- pins. Vin pin and Vcc pins should be shorted together for external Vcc operation by installing a 0 ohm resistor at R4. The board is configured for remote sensing. If local sense is desired, R18 should be uninstalled and R19 should be installed instead. External Enable signal can be applied to the board via exposed Enable pad and R100 should be removed for this purpose. Table I. Connections Connection Signal Name VIN+ Vin (+12V) VIN- Ground of Vin Vout+ Vout(+1.2V) Vout- Ground for Vout Vcc+ Vcc Pin Vcc- Ground for Vcc input Enable Enable PGood Power Good Signal AGnd Analog ground LAYOUT The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3846 and most of the passive components are mounted on the top side of the board. Power supply decoupling capacitors and feedback components are located close to IR3846. The feedback resistors are connected to the output of the remote sense amplifier of the IR3846 and are located close to the IR3846. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. Separate power ground and analog ground are used and may be connected together using a 0 ohm resistor at R71. 9/11/2013 2 AL IRDC3846-P1V2 CONNECTIONS and OPERATING INSTRUCTIONS LAYOUT The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3846 and most of the passive components are mounted on the top side of the board. Power supply decoupling capacitors and feedback components are located close to IR3846. The feedback resistors are connected to the output of the remote sense amplifier of the IR3846 and are located close to the IR3846. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. Separate power ground and analog ground are used and may be connected together using a 0 ohm resistor at R71. Vin Gnd Gnd Vo Top View 9/11/2013 3 AL Vin Vp PGD PGood PG_PU PG_Pullup Rt/Sy nc N/S D1 Sy nc Sy nc Vp Vref Vref Vin Agnd 1 Vcc- 1 Vcc+ 1 4 OCSelect 2 VCC Enable 1 3 C19 N/S 0 R3 4pin jumper 1 1 1 1 1 1 2 1 1 PVin C5 N/S R16 4.02K R9 39.2K RT/Sy nc BOOT 4.02K R14 R17 4.02K Vsns R101 7.5K R100 49.9K C71 22uF C72 22uF C73 22uF C74 22uF C75 22uF C76 22uF C77 22uF C78 N/S OCset RT/Sy nc Enable BOOT NC2 NC1 PVin R11 C14 N/S C13 2200pF C11 8.2nF IR3846 0 R10 R15 20 R18 0 C16 N/S 20 Vin 0 R116 0 R71 Vin N/S R49 N/S R48 0 R47 0 R46 6 5 4 3 2 1 6 5 4 3 2 1 Vin- Vin+ R110 10K JUMPER 3 BODE2 C6 1uF L1 C15 N/S Vo_R_N Vo_R_P R113 N/S R112 N/S Vin 2 Vout N/S D2 11 C100-C124: 0805 / 1206 pads Optional Pre-Bias test circuit VPB N/S N/S + C125 N/S N/S N/S 1 N/S Ground and Signal ( “analog” ) Ground N/S N/S R40 + C127 N/S Vout_Adj + C126 N/S N/S C109 C110 C111 C116 C117 C118 N/S N/S N/S N/S N/S C40 N/S M2 N/S N/S Optional "1-bit VID" circuit FB N/S + C129 Vin N/S N/S N/S R41 N/S N/S + C128 N/S N/S C119 C120 C121 C122 C123 C124 100uF 100uF 100uF 100uF 100uF 100uF N/S C100 C101 C102 C103 C104 C105 C106 C107 C108 C113 C114 C115 C112 0.1uF C130 6 x 100uF / 1206 / 6.3V / Ceramic Capacitor Single point of connection between Power Vout Vp R111 10K VDDQ 250nH WE744309025 330uF / 25V / Electrolytic Capacitor 330uF + C81 0 R115 N/S R4 C8 10uF C80 N/S N/S R70 0 R118 N/S R117 17 Vref 18 19 PGD C17 100pF VCC 21 VCC 22 23 BODE1 JUMPER 2 R19 N/S S_Ctrl Vref Vp PGD Vin VCC NC3 NC4 SW 24 SW C79 N/S 1 Fig. 1: Schematic of the IRDC3846 evaluation board 4.02K R13 127 R12 2.7K 160pF C12 R114 N/S 7 6 5 4 3 2 1 U1 0.1uF C10 BOOT 7 x 22uF / 1206 / 25V / Ceramic Capacitor C70 0.1uF 26 NC5 PVin VCC C71-C80: 0805 / 1206 pads PG_PU PVin FB Vin FB Vsns 8 Vsns 9 FB Comp 10 RSo 11 PGND 12 LGND 13 S_Ctrl 14 1 RS15 RS+ 16 1 1 Vin 1 1 9/11/2013 1 R46-R49: 1206 pads 6 5 4 3 2 1 6 5 4 3 2 1 Vout- Vout+ Vout IRDC3846-P1V2 4 AL IRDC3846-P1V2 Schematic for Transient Load set up ExtLoadCtrl 3 1 VCC N/S R34 N/S 2 1 S3 SW N/S R35 N/S R36 C30 N/S U2 N/S R30 1 2 3 4 VS VS IN OUT2 N/A OUT1 GND GND 8 7 6 5 D3 N/S N/S R38 N/S R39 Vout M1 IRF6721 N/S D4 N/S 1 MIC4452/SO8 N/S R31 N/S C31 N/S R32 N/S C32 N/S Vout N/S R37 R33 N/S I-Monitor Vo_R_P C33 N/S Vo_R_N Optional transient load circuit 9/11/2013 5 AL IRDC3846-P1V2 Bill of Materials Item Qty Part Reference Value Description Manufacturer C71 C72 C73 1 7 C74 C75 C76 22uF 1206, 25V, X5R, 10% Murata C77 C6 1uF 0603, X5R, 25V, 20% TDK 2 1 C8 10uF 0603, X5R, 10V, 20% TDK 3 1 4 3 C10 C70 C130 0.1uF 0603, 25V, X7R, 10% Murata 5 1 C11 8200pF 0603, 50V, X7R, 10% Murata 6 1 C12 160pF 0603, 50V, NP0, 5% Murata 7 1 C13 2200pF 0603, 50V, X7R, 10% Murata 8 1 C17 100pF 0603, 50V, C0G, 5% Murata SMD Elecrolytic, Fsize, 9 Panasonic 1 C81 330uF 25V, 20% 250nH, Wurth 10 1 L1 250nH DCR=0.165mohm Electronics Inc. C101 C102 C103 11 6 100uF 1206, 6.3V, X5R, 20% Murata C104 C105 C106 R3 R10 R18 12 6 0 0603,1/10W, Jumper Vishay/Dale R115 R116 R118 13 1 R9 39.2K 0603,1/10W,1% Panasonic 14 1 R11 2.7K 0603,1/10W,1% Panasonic 15 1 R12 127 0603,1/10W,1% Panasonic R13 R14 R16 16 4 4.02 K 0603,1/10W,1% Panasonic R17 17 1 R15 20 0603,1/10W,1% Vishay/Dale 18 2 R46 R47 0 1206,1/4W, Jumper Yageo 19 1 R71 0 0402, 1/16W, Jumper Yageo 20 1 R100 49.9K 0603,1/10 W,1% Panasonic 21 1 R101 7.5K 0603,1/10W,1% Panasonic 22 2 R110 R111 10K 0603,1/10 W,1% Panasonic PLUG 40 POS DBL Omron 23 1 Jumper ROW STR Electronics Inc. Keystone 24 2 Vin+ Vout+ RED SCREW TERMINAL Electronics Keystone 25 2 Vin- VoutBLACK SCREW TERMINAL Electronics International 26 1 U1 IR3846 IR3846 5mm X 7mm Rectifier 9/11/2013 Part Number GRM31CR61E226KE15L C1608X5R1E105M C1608X5R1A106M GRM188R71E104KA01D GRM188R71H822KA01D GRM1885C1H161JA01D GRM188R71H222KA01D GRM1885C1H101JA01D EEV-FK1E331P 744309025 GRM31CR60J107ME39L CRCW06030000Z0EA ERJ-3EKF3922V ERJ-3EKF2701V ERJ-3EKF1270V ERJ-3EKF4021V CRCW060320R0FKEA RC1206JR-070RL RC0402JR-070RL ERJ-3EKF4992V ERJ-3EKF7501V ERJ-3EKF1002V XG8W-4041-ND 8199-2 8199-3 IR3846MPBF 6 AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0A-35A, Fsw=600kHz, Room Temperature, No air flow Fig. 2: Start up at 35A Load Ch1:Vin, Ch2:Vo, Ch3:PGood, Ch4:Enable Fig. 4: Start up with 1.08V Pre Bias, 0A Load Ch2:Vo, Ch3:PGood Fig. 6: Inductor node at 35A load Ch2:LX 9/11/2013 Fig. 3: Start up at 35A Load Ch1:Vin, Ch2:Vo, Ch3:PGood, Ch4:Vcc Fig. 5: Output Voltage Ripple, 35A load Ch1: Vo Fig. 7: Short (Hiccup) Recovery Ch2:Vo, Ch3:PGood, Ch4:Io 7 AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=3.5A-14A, Fsw=600kHz, Room Temperature, No air flow Fig. 8: Transient Response, 3.5A to 14A step (2.5A/us) Ch2:Vo 9/11/2013 8 AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=24.5A-35.0A, Fsw=600kHz, Room Temperature, No air flow Fig. 9: Transient Response, 24.5A to 35A step (2.5A/us) Ch2:Vo 9/11/2013 9 AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0A-35A, Fsw=600kHz, Room Temperature, No air flow Fig. 10: Bode Plot at 35A load: Fo = 100.6kHz; Phase Margin = 52.8º; Gain Margin = -17.2dB 9/11/2013 10 AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0A-35A, Fsw=600kHz, Room Temperature, No air flow 91 89 Efficiency [%] 87 85 83 81 79 77 75 73 71 0 5 10 15 20 25 30 35 25 30 35 Io [A] Power Loss [W] Fig.11: Efficiency versus load current 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 5 10 15 20 Io [A] Fig.12: Power loss versus load current 9/11/2013 11 AL IRDC3846-P1V2 THERMAL IMAGES Vin=12.0V, Vo=1.2V, Io=35A, Fsw=600kHz, Room Temperature, No air flow Fig. 13: Thermal Image of the board at 35A load Test point 1 is IR3846: 98.80C Test point 2 is inductor: 72.90C 9/11/2013 12 AL IRDC3846-P1V2 THERMAL IMAGES Vin=12.0V, Vo=1.2V, Io=35A, Fsw=600kHz, Room Temperature, LFM = 100 Fig. 14: Thermal Image of the board at 35A load Test point 1 is IR3846: 740C Test point 2 is inductor: 46.90C 9/11/2013 13 AL IRDC3846-P1V2 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. 9/11/2013 14 AL