IRDC3847-P1V2 SupIRBuck TM USER GUIDE FOR IR3847 EVALUATION BOARD DESCRIPTION The IR3847 is a synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mmx6mm QFN package. Key features offered by the IR3847 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 IR3847 evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3847 is available in the IR3847 data sheet. BOARD FEATURES • Vin = +12V (+ 13.2V Max), No Vcc required. • Vout = +1.2V @ 0-25A • Fs=600kHz • L= 0.215uH • Cin= 7x22uF (ceramic 1206) + 1x330uF (electrolytic) • Cout=10x47uF (ceramic 0805) 4/11/2013 1 IRDC3847-P1V2 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 25A load should be connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I. IR3847 needs only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc is required, then R33 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 R35. The board is configured for remote sensing. If local sense is desired, R8 should be uninstalled and R16 should be installed instead. External Enable signal can be applied to the board via exposed Enable pad and R18 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 IR3847 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 IR3847. The feedback resistors are connected to the output of the remote sense amplifier of the IR3847 and are located close to the IR3847. 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 one of three possible locations. It is preferred to use one of R43 or R44. 4/11/2013 2 IRDC3847-P1V2 CONNECTIONS and OPERATING INSTRUCTIONS LAYOUT The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3847 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 IR3847. The feedback resistors are connected to the output of the remote sense amplifier of the IR3847 and are located close to the IR3847. 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 one of three possible locations. It is preferred to use one of R43 or R44. Vin Gnd Gnd Vo Top View 4/11/2013 3 1 D2 N/S 11 2 Vout PG_PU PG_Pullup N/S C9 1 Vout_Adj R26 N/S C52 N/S M3 Fb Vcc- 4 OCSelect 2 1 3 R9 39.2K 19 28 30 31 33 Rt/Sy nc 4 5 Vp NC0 NC1 NC2 NC3 NC4 Rt/Sy nc OCSelect PGD Vcc Comp FB RSo Vref IR3847 1 N/S R2 4.22K N/S R21 C8 Vsns 2200pF 4.22K 127 C50 N/S 0.1uF C37 C39 0 C56 N/S C54 N/S R28 1uF C55 N/S C25 0.1uF R3 Fb 13 6 20 21 22 23 24 25 32 2 26 C57 22uF R4 RS+ Vsns SW SW SW SW SW SW SW Boot PGnd Vin R33 0 49.9K R35 VCC R18 N/S C38 C24 0.1uF C7 22uF BODE JUMPER 2 R6 20 0 R11 N/S R12 0 R10 4.22K R32 C6 22uF C5 22uF L1 R20 N/S Vout Vsns N/S C45 47uF 47uF 47uF C20 47uF C19 47uF C18 0 ohm 47uF C17 47uF C16 N/S C44 0 R44 N/S R43 N/S C42 N/S N/S C43 C40 N/S C41 47uF C21 47uF C22 + C35 N/S + C36 N/S Ground and Signal ( “analog” ) Ground + C51 N/S C14 0.1uF Vin- Vin+ Vout 6 5 4 3 2 1 6 5 4 3 2 1 + C34 N/S 47uF C15 25V 330uF C2 + C1 22uF 330uF R30 0 ohm 10 x 47uF / 0805 / 6.3V Ceramic N/S N/S 0.1uF C28 C3 22uF PVin R31 Single point of connection between Power N/S R16 Vo_R_N Vo_R_P 4.22K R15 C29 C33 C30 C27 C4 22uF 7 x 22uF / 1206 / 25V Ceramic C31 N/S 215nH PCDC1008-R215EMO SWs C32 N/S Fig. 1: Schematic of the IR3847 evaluation board Agnd 4pin jumper C68 N/S R17 10K 16 PGD 8 7 9 U3 PG_PU R29 10K Vcc+ 8.2nF C26 C11 160pF 0 R8 R19 7.5K 18 C66 10uF VCC 1.91K R1 Optional "1-bit VID" circuit N/S N/S R27 PGD PGood Vp Vp R41 N/S R40 N/S Vp VDDQ Optional Pre-Bias test circuit VPB Rt/Sy nc N/S D3 Sy nc Sy nc 100pF C10 1 1 2 1 Vref 1 1 1 15 Vp Vref 1 1 1 17 Vin 1 3 Enable Vref 14 LGnd 11 1 PVin PGnd PGnd PGnd 10 27 29 RS12 4/11/2013 1 Enable 6 5 4 3 2 1 6 5 4 3 2 1 Vout- Vout+ IRDC3847-P1V2 4 IRDC3847-P1V2 Schematic for Transient Load set up Vout VCC 3 1 R22 ExtLoadCtrl R23 2 1 N/S N/S S3 SW N/S R24 Vo_R_P N/S R36 N/S U2 1 2 3 4 R39 N/S C46 N/S C49 N/S VS VS IN OUT2 N/A OUT1 GND GND 8 7 6 5 MIC4452/SO8 N/S R37 N/S R53 100 R54 100 D7 ZHCS350 D6 ZHCS350 R25 M1 IRF6721 N/S Vout N/S C47 N/S C48 N/S 1 R38 N/S C58 N/S C59 N/S C60 N/S C61 N/S C62 22uF C65 N/S C64 N/S C63 N/S I-Monitor Vo_R_N Optional transient load circuit 4/11/2013 5 IRDC3847-P1V2 Bill of Materials Item Quantity Part Reference Value C2 C3 C4 C5 C6 C7 22uF C57 1 7 2 1 3 6 4 5 1 1 6 10 7 8 9 10 11 12 13 14 1 1 1 1 1 1 1 1 15 7 16 17 18 19 20 21 22 1 1 2 2 1 1 2 23 1 Jumper 24 25 26 2 2 1 Vin+ Vout+ Vin- VoutU1 4/11/2013 C1 330uF C9 C14 C24 C25 0.1uF C37 C33 C8 2200pF C11 160pF C16 C17 C18 C19 C20 C27 C28 C29 47uF C30 C36 C26 8.2nF L1 0.215uH R1 1.91K R2 4.22K R3 4.22K R4 127 R6 20 R9 39.2K R8 R28 R10 R11 0 R44 R33 R34 C39 1uF C66 10uF R15 R32 4.22K R30 R31 0 R18 49.9K R19 7.5K R17 R29 10K RED BLACK IR3847 Description Manufacturer Part Number 1206, 25V, X5R, 10% Murata GRM31CR61E226KE15L SMD Elecrolytic, Fsize, 25V, 20% Panasonic EEV-FK1E331P 0603, 25V, X7R, 10% Murata GRM188R71E104KA01D 2200pF,0603,50V,X7R 50V, 0603, NP0, 5% Murata Murata GRM188R71H222KA01D GRM1885C1H161JA01D 0805, 6.3V, X5R, 20% TDK C2012X5R0J476M 0603, 50V, X7R, 10% 0.215uH, DCR=0.29mohm 0603,1/10W,1% 0603,1/10W,1% 0603,1/10W,1% 0603,1/10W,1% 0603,1/10 W,1% 0603,1/10 W,1% Murata Cyntec Panasonic Panasonic Panasonic Panasonic Vishay/Dale Panasonic GRM188R71H822KA01D PCDC1008-R215EMO ERJ-3EKF1911V ERJ-3EKF4221V ERJ-3EKF4221V ERJ-3EKF1270V CRCW060320R0FKEA ERJ-3EKF3922V 0603,1/10 W,5% Vishay/Dale CRCW06030000Z0EA 0603, X5R, 25V, 20% 0603, X5R, 10V, 20% 0603,1/10 W,1% 1206,1/4 W, 5% 0603,1/10 W,1% 0603,1/10 W,1% 0603,1/10 W,1% PLUG 40 POS DBL ROW STR SCREW TERMINAL SCREW TERMINAL IR3847 5mm X6mm TDK TDK Panasonic Yageo Panasonic Panasonic Panasonic C1608X5R1E105M C1608X5R1A106M ERJ-3EKF4221V RC1206JR-070RL ERJ-3EKF4992V ERJ-3EKF7501V ERJ-3EKF1002V Omron Electronics Inc. XG8W-4041-ND Keystone Electronics Keystone Electronics International Rectifier 8199-2 8199-3 IR3847MPBF 6 IRDC3847-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow Fig. 2: Start up at 25A Load Ch1:Vin, Ch2:Vo, Ch3:PGood, Ch4:Enable Fig. 4: Start up with 1.08V Pre Bias, 0A Load Ch1:Enable, Ch2:Vout, Ch3:PGood Fig. 6: Inductor node at 25A load Ch2:LX 4/11/2013 Fig. 3: Start up at 25A Load Ch1:Vin, Ch2:Vo, Ch3:PGood,Ch4:Vcc Fig. 5: Output Voltage Ripple, 25A load Ch1: Vout Fig. 7: Short (Hiccup) Recovery Ch2:Vout , Ch3:PGood, Ch4:Iout 7 IRDC3847-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=2.5A-12.5A, Fsw=600kHz, Room Temperature, No air flow Fig. 8: Transient Response, 2.5A to 12.5A step (2.5A/us) Ch2:Vout, Ch4:Iout(10A/V) 4/11/2013 8 IRDC3847-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=15A-25A, Fsw=600kHz, Room Temperature, No air flow Fig. 9: Transient Response, 15A to 25A step (2.5A/us) Ch2:Vout, Ch4:Iout(10A/V) 4/11/2013 9 IRDC3847-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow Fig. 10: Bode Plot at 25A load: Fo = 108.0kHz; Phase Margin = 50.2º 4/11/2013 10 IRDC3847-P1V2 Efficiency [%] TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow 92 90 88 86 84 82 80 78 76 74 72 70 0 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 Io [A] Fig.11: Efficiency versus load current 5.0 4.5 Power Loss [W] 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 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 Io [A] Fig.12: Power loss versus load current 4/11/2013 11 IRDC3847-P1V2 THERMAL IMAGES Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow Fig. 13: Thermal Image of the board at 25A load Test point 1 is IR3847: 750C Test point 2 is inductor: 61.50C 4/11/2013 12 IRDC3847-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. 10/11 4/11/2013 13