IRDC3846-P3V3 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 = +3.3V @ 0-35A • Fs=300kHz • L= 1.0uH • Cin= 6x22uF (ceramic 1210) + 4x22uF (ceramic 1206) + 1x330uF (electrolytic) • Cout= 5x120uF (SP) + 1x47uF (ceramic 0805) 12/4/2013 1 AL IRDC3846-P3V3 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(+3.3V) 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. 12/4/2013 2 AL IRDC3846-P3V3 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 12/4/2013 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 N/S R17 1.47K Vsns R101 7.5K R100 49.9K C71 22uF C72 22uF C73 22uF C74 22uF C75 22uF C76 22uF C77 22uF C78 22uF R14 R16 6.65K R9 82.5K RT/Sy nc BOOT OCset RT/Sy nc Enable BOOT NC2 NC1 PVin C12 IR3846 C14 N/S C13 3300pF C11 1.8nF 2 R10 R15 20 R18 0 C16 N/S 20 Vin 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 Vin 2 Vout N/S D2 11 C100-C124: 0805 / 1206 pads Optional Pre-Bias test circuit VPB N/S N/S N/S N/S N/S N/S N/S + C126 120uF N/S N/S + C127 120uF N/S N/S N/S 1 Vout_Adj N/S R40 Ground and Signal ( “analog” ) Ground N/S N/S N/S N/S + C128 120uF N/S C40 N/S M2 Vin N/S N/S Optional "1-bit VID" circuit N/S N/S R41 FB N/S + C129 120uF N/S C119 C120 C121 C122 C123 C124 N/S 5 x 120uF / 6.3V / SP Capacitor + C125 120uF 47uF N/S C109 C110 C111 C116 C117 C118 N/S C100 C101 C102 C103 C104 C105 C106 C107 C108 C113 C114 C115 C112 1 x 47uF / 0805 / 6.3V / Ceramic Capacitor Single point of connection between Power Vout Vp R112 N/S VDDQ R111 10K 1uH 330uF / 25V / Electrolytic Capacitor 330uF + C81 0 R115 N/S R4 C8 10uF C80 22uF N/S R70 0 R118 158 R117 715 R116 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 22uF 1 Fig. 1: Schematic of the IRDC3846 evaluation board 7.32K R13 549 R12 30K R11 36pF R114 N/S 7 6 5 4 3 2 1 U1 0.1uF C10 BOOT 4 x 22uF / 1206 / 25V / Ceramic Capacitor 6 x 22uF / 1210 / 25V / Ceramic Capacitor C70 0.1uF 26 PVin VCC C71-C80: 0805 / 1206 pads 1 1 Vin PG_PU PVin FB Vin FB Vsns 8 Vsns 9 FB Comp 10 RSo 11 PGND 12 NC5 LGND 13 S_Ctrl 14 1 RS15 RS+ 16 1 1 12/4/2013 1 R46-R49: 1206 pads N/S C130 6 5 4 3 2 1 6 5 4 3 2 1 Vout- Vout+ Vout IRDC3846-P3V3 4 AL IRDC3846-P3V3 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 N/S R38 N/S R39 MIC4452/SO8 N/S R31 N/S C31 N/S D3 N/S R32 N/S Vout M1 IRF6721 N/S D4 N/S N/S R37 1 C32 N/S Vout R33 N/S I-Monitor Vo_R_P C33 0.1uF Vo_R_N Optional transient load circuit 12/4/2013 5 AL IRDC3846-P3V3 Bill of Materials Item Qty Part Reference Value 1 4 C74 C75 C79 C80 22uF C71 C72 C73 C76 22uF 2 6 C77 C78 C6 1uF 3 1 C8 10uF 4 1 5 3 C10 C33 C70 0.1uF 6 1 C11 1.8nF 7 1 C12 36pF 8 1 C13 3300pF 9 1 C17 100pF Description 1206, 25V, X5R, 10% Manufacturer Murata Part Number GRM31CR61E226KE15L 1210, 25V, X5R, 20% Taiyo Yuden TMK325BJ226MM-T 0603, X5R, 25V, 20% 0603, X5R, 10V, 20% 0603, 25V, X7R, 10% 0603, 50V, X7R, 10% 0603, 50V, NP0, 5% 0603, 50V, X7R, 10% 0603, 50V, NP0, 5% SMD Elecrolytic, Fsize, 25V, 20% 1uH, DCR=0.93mohm 0805, 6.3V, X5R, 20% TDK TDK Murata Murata Murata Murata Murata C1608X5R1E105M C1608X5R1A106M GRM188R71E104KA01D GRM188R71H182KA01D GRM1885C1H360JA01D GRM188R71H332KA01D GRM1885C1H101JA01D Panasonic EEE-FK1E331P Coilcraft TDK XAL1580-102ME_ C2012X5R0J476M Panasonic EEF-UD0J121R 10 1 11 12 1 1 13 5 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 4 1 1 1 1 1 1 1 1 2 1 1 1 2 1 1 30 1 Jumper 31 2 Vin+ Vout+ RED 32 2 Vin- Vout- BLACK SCREW TERMINAL 33 1 U1 IR3846 IR3846 5mm X 7mm C81 330uF L1 1uH C109 47uF C125 C126 C127 120uF C128 C129 R3 R18 R115 R118 0 R9 82.5K R10 2 R11 30K R12 549 R13 7.32K R16 6.65K R17 1.47K R15 20 R46 R47 0 R71 0 R100 49.9K R101 7.5K R110 R111 10K R116 715 R117 158 12/4/2013 6.3V, 20%,15mΩ 0603,1/10W, Jumper Vishay/Dale 0603,1/10W,1% Panasonic 0603,1/10W,5% Panasonic 0603,1/10W,1% Panasonic 0603,1/10W,1% Panasonic 0603,1/10W,1% Panasonic 0603,1/10W,1% Panasonic 0603,1/10W,1% Panasonic 0603,1/10W,1% Vishay/Dale 1206,1/4W, Jumper Yageo 0402, 1/16W, Jumper Yageo 0603,1/10 W,1% Panasonic 0603,1/10 W,1% Panasonic 0603,1/10 W,1% Panasonic 0603,1/10 W,1% Panasonic 0603,1/10 W,1% Panasonic PLUG 40 POS DBL ROW Omron STR Electronics Inc. Keystone SCREW TERMINAL Electronics Keystone Electronics International Rectifier CRCW06030000Z0EA ERJ-3EKF8252V ERJ-3GEYJ2R0V ERJ-3EKF3002V ERJ-3EKF5490V ERJ-3EKF7321V ERJ-3EKF6651V ERJ-3EKF1471V CRCW060320R0FKEA RC1206JR-070RL RC0402JR-070RL ERJ-3EKF4992V ERJ-3EKF7501V ERJ-3EKF1002V ERJ-3EKF7150V ERJ-3EKF1580V XG8W-4041-ND 8199-2 8199-3 IR3846MPBF 6 AL IRDC3846-P3V3 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=3.3V, Io=0A-35A, Fsw=300kHz, 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 2.97V Pre Bias, 0A Load Ch2:Vo, Ch3:PGood Fig. 6: Inductor node at 35A load Ch2:LX 12/4/2013 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-P3V3 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=3.3V, Io=0A-17.5A, Fsw=300kHz, Room Temperature, No air flow Fig. 8: Transient Response, 0A to 17.5A step (2.5A/us) Ch2:Vo, Ch4:Io 12/4/2013 8 AL IRDC3846-P3V3 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=3.3V, Io=17.5A-35.0A, Fsw=300kHz, Room Temperature, No air flow Fig. 9: Transient Response, 17.5A to 35A step (2.5A/us) Ch2:Vo, Ch4:Io 12/4/2013 9 AL IRDC3846-P3V3 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=3.3V, Io=35A, Fsw=300kHz, Room Temperature, No air flow Fig. 10: Bode Plot at 35A load: Fo = 36.9kHz; Phase Margin = 56.6º; Gain Margin = -24.7dB 12/4/2013 10 AL IRDC3846-P3V3 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=3.3V, Io=0A-35A, Fsw=300kHz, Room Temperature, No air flow 97 95 Efficiency [%] 93 91 89 87 85 83 81 79 77 0 5 10 15 20 25 30 35 25 30 35 Io [A] Power Loss [W] Fig.11: Efficiency versus load current 9.0 8.5 8.0 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 12/4/2013 11 AL IRDC3846-P3V3 THERMAL IMAGES Vin=12.0V, Vo=3.3V, Io=35A, Fsw=300kHz, Room Temperature, LFM = 100 Fig. 13: Thermal Image of the board at 35A load IR3846: 74.10C Inductor: 53.20C Ambient: 24.80C 12/4/2013 12 AL IRDC3846-P3V3 THERMAL IMAGES Vin=12.0V, Vo=3.3V, Io=35A, Fsw=300kHz, Room Temperature, LFM = 200 Fig. 14: Thermal Image of the board at 35A load IR3846: 69.70C Inductor: 49.40C Ambient: 24.10C 12/4/2013 13 AL IRDC3846-P3V3 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. 12/4/2013 14 AL