SupIRBuck TM IRDC3447-P0V9 USER GUIDE FOR IR3447 EVALUATION BOARD DESCRIPTION BOARD FEATURES

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1 SupIRBuck TM USER GUIDE FOR IR3447 EVUATION BOARD DESCRIPTION IRDC3447-P0V9 The IR3447 is a synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mmx6mm QFN package. Key features offered by the IR3447 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 IR3447 evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3447 is available in the IR3447 data sheet. BOARD FEATURES V in = +2V, No Vcc required. V out = 0-20A F s =750kHz L= 0.50uH C in = 5x22uF (ceramic 206) + x330uf (electrolytic) C out =2x (ceramic 0805) 2/7/205

2 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +2V input supply should be connected to VIN+ and VIN-. A maximum of 20A load should be connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I. IR3447 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 R6 should be installed instead. External Enable signal can be applied to the board via exposed Enable pad and R8 should be removed for this purpose. Table I. Connections Connection VIN+ VIN- Vout+ Vout- Vcc+ Vcc- Enable PGood Signal Name Vin (+2V) Ground of Vin Vout(+0.9V) Ground for Vout Vcc Pin Ground for Vcc input Enable Power Good Signal AGnd Analog ground LAYOUT The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3447 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 IR3447. The feedback resistors are connected to the output of the remote sense amplifier of the IR3447 and are located close to the IR3447. 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. 2/7/205 2

3 CONNECTIONS and OPERATING INSTRUCTIONS LAYOUT The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3447 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 IR3447. The feedback resistors are connected to the output of the remote sense amplifier of the IR3447 and are located close to the IR3447. 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 2/7/205 3

4 R3 Enable 0 ohm Vin+ R8 49.9K PVin R Vref Vref R40 Vp Vref C50 50nH R0 0 L C2 C22 C4 0.uF BODE R44 0 R27 Fb Vout_Adj R26 M3 C52 Single point of connection between Power Ground and Signal ( analog ) Ground Optional "-bit VID" circuit Fig. : Schematic of the IR3447 evaluation board Vout+ C0 00pF Vp R8 0 R9 7.5K R35 C25 0.uF C55 C39 uf R28 0 C56 SWs C32 C38 C3 C 220pF U IR3447 R33 0 Coilcraft FP07R-R5-R R32 2.7K 5 x 22uF / 206 / 25V Ceramic Vsns C6 22uF C45 C44 C5 22uF 2 x / 0805 / 6.3V Ceramic C42 C4 22uF C43 C27 C40 C3 22uF C20 C4 C9 + C C8 330uF 25V 330uF C7 C35 0 ohm C6 C5 R pF Fb R6 R3 R2 20 R6 Optional Pre-Bias test circuit Vsns + + C36 C34 C Vin 7 C9 R C26 R4.96K 2nF 9 7 Vcc+ VCC 8 8 PG_PU R29 0K PGD 6 5 R7 0K Sy nc PG_Pullup Vp PGood Rt/Sync 4 OCSelect Sy nc PG_PU Vp PGD 28 C uF 3 D3 33 4pin jumper C68 Rt/Sync R9 FB Comp Vcc PGD OCSelect Rt/Sync PGnd Boot SW 20 SW 2 SW 22 SW 23 SW 24 SW 25 SW 32 Vsns 26 PVin RSo RS+ 2 4 NC5 Cbyp Enable LGnd PGnd PGnd PGnd Vcc- RS K NC0 NC NC2 NC3 NC4 Vin R2 R 0 R20 C24 0.uF R5 6.34K C30 C29 C28 C2 22uF Vout C8 Agnd Vo_R_P C K 6.34K VPB R43 D2 R2 C54 JUMPER 2 2 Vout Vout- VDDQ VCC C37 0.uF Vout Vo_R_N Vin- C57 C33 2/7/205 4

5 IRDC3447-P0V9 Schematic for Transient Load set up Vout VCC ExtLoadCtrl 3 2 S3 SW R22 R23 R24 R39 0K R36 C49 0.uF U2 8 2 VS VS 7 3 IN OUT2 6 4 N/A OUT 5 GND GND MIC4452/SO8 C46 0uF R37 0K R R D7 RB75S40,5 D6 RB75S40,5 M IRF672 C48 00pF R I-Monitor C47 0.uF C58 C59 Vo_R_P Vout C60 C6 C62 C65 C64 C63 R Vo_R_N Optional transient load circuit 2/7/205 5

6 Bill of Materials Item Quantity Part Reference Value Description Manufacturer Part Number C 330uF SMD Elecrolytic, Fsize, 25V, 20% Panasonic EEV-FKE33P 2 5 C2 C3 C4 C5 C6 22uF 206, 25V, X5R, 0% Murata GRM3CR6E226KE5L 3 C8 2200pF 0603, 50V, X7R, 0% Murata GRM88R7H222KA0D 4 2 C0 C48 00pF 0603, 50V, C0G, 5% Murata GRM885CH0JA0D 5 C 220pF 0603, 50V, NP0, 5% Murata GRM885CH22JA0D 6 6 C4 C24 C25 C37 C47 C49 0.uF 0603, 25V, X7R, 0% Murata GRM88R7E04KA0D 7 2 C5 C6 C7 C8 C9 C20 C2 C , 6.3V, X5R, 20% TDK C202X5R0J476M25AC C27 C28 C40 C4 8 C26 2nF 0603, 50V, X7R, 0% Murata GRM88R7H23KA0D 9 L 50nH L=50nH, DCR=0.29mΩ, Isat=55A 7.2 x.0 x 7.5mm Coiltronics FP07R-R5-R 0 R.96K 0603,/0W,% Panasonic ERJ-3EKF96V 2 R2 R5 6.34K 0603,/0W,% Panasonic ERJ-3EKF634V 2 2 R3 R32 2.7K 0603,/0W,% Panasonic ERJ-3EKF272V 3 R ,/0W,% Panasonic ERJ-3EKF30V 4 R ,/0W,% Vishay/Dale CRCW060320R0FKEA 5 R9 3.6K 0603,/0W,% Panasonic ERJ-3EKF362V 6 6 R8 R0 R R28 R33 R ,/0W,5% Vishay/Dale CRCW Z0EA 7 C39 uf 0603, 25V, X5R, 20% TDK C608X5RE05M 8 C66 0uF 0603, 0V, X5R, 20% TDK C608X5RA06M 9 2 D6 D7 NXP Diode Schottky 40V 0.2A SOD523 Semiconductors RB75S40,5 20 M IRF672 MOSFET N-CH 30V 4A International Rectifier IRF672STRPBF 2 2 R30 R ,/4 W, 5% Yageo RC206JR-070RL 22 R8 49.9K 0603,/0 W,% Panasonic ERJ-3EKF4992V 23 R9 7.5K 0603,/0 W,% Panasonic ERJ-3EKF750V 24 4 R7 R29 R37 R39 0K 0603,/0 W,% Panasonic ERJ-3EKF002V 25 3 R22 R23 R ,/0 W,% Panasonic ERJ-3GEYJR0V 26 R ,/8W,5% CTS Resistor Products 73L3R20J 28 R ,/2W,% Ohmite LVK2R020FER 29 R ,/0 W,% Panasonic ERJ-3EKF3000V 30 R ,/0 W,% Panasonic ERJ-3EKF5490V 3 Jumper PLUG 40 POS DBL ROW STR Omron Electronics Inc. XG8W-404-ND 32 2 Vin+ Vout+ RED SCREW TERMIN Keystone Electronics Vin- Vout- BLACK SCREW TERMIN Keystone Electronics U IR3447 IR3447 5mm X 6mm International Rectifier IR U2 MIC4452 MOSFET Driver Non-inverting SO-8 / SO8 Micrel MIC4452YM 2/7/205 6

7 TYPIC OPERATING WAVEFORMS Vin=2.0V, Vo=0.9V, Io=0A-20A, Fsw=750kHz, Room Temperature, No air flow Fig. 2: Start up at 20A Load Ch :V in, Ch 2 :Vout, Ch 3 :PGood, Ch 4 :Enable Fig. 3: Start up at 20A Load Ch :V in, Ch 2 :Vout, Ch 3 :PGood, Ch 4 :V cc Fig. 4: Start up with 0.63V Pre Bias, 0A Load Ch :Enable, Ch 2 :Vout, Ch 3 :PGood Fig. 5: Output Voltage Ripple, 20A load Ch : Vout Fig. 6: Inductor node at 20A load Ch 2 :LX Fig. 7: Short (Hiccup) Recovery Ch 2 :Vout, Ch 3 :PGood, Ch 4 :Iout 2/7/205 7

8 TYPIC OPERATING WAVEFORMS Vin=2.0V, Vo=0.9V, Io=3.0A-9.0A, Fsw=750kHz, Room Temperature, No air flow Fig. 8: Transient Response, 3A to 9A step (28A/us) Ch 2 :Vout 2/7/205 8

9 TYPIC OPERATING WAVEFORMS Vin=2.0V, Vo=0.9V, Io=4A-20A, Fsw=750kHz, Room Temperature, No air flow Fig. 9: Transient Response, 4A to 20A step (28A/us) Ch 2 :Vout 2/7/205 9

10 TYPIC OPERATING WAVEFORMS Vin=2.0V, Vo=0.9V, Io=20A, Fsw=750kHz, Room Temperature, No air flow Fig. 0: Bode Plot at 20A load: Fo = 02.3kHz; Phase Margin = 54.4º; Gain Margin =-2.7dB 2/7/205 0

11 TYPIC OPERATING WAVEFORMS Vin=2.0V, Vo=0.9V, Io=0A-20A, Fsw=750kHz, Room Temperature, No air flow Efficiency [%] Io [A] Fig.: Efficiency versus load current Power Loss [W] Io [A] Fig.2: Power loss versus load current 2/7/205

12 THERM IMAGES Vin=2.0V, Vo=0.9V, Io=20A, Fsw=750kHz, Room Temperature, No air flow Fig. 3: Thermal Image of the board at 20A load IR3447: C Inductor: C Ambient: C 2/7/205 2

13 IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (30) TAC Fax: (30) Visit us at for sales contact information Data and specifications subject to change without notice. 0/ 2/7/205 3