SupIRBuck TM IRDC3846-P1V2 USER GUIDE FOR IRDC3846 EVALUATION BOARD DESCRIPTION BOARD FEATURES

Transcription

1 SupIRBuck TM USER GUIDE FOR IRDC3846 EVUATION BOARD DESCRIPTION IRDC3846-PV2 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 V in = +2V, No Vcc required. V out = 0-35A F s =600kHz L= 0.250uH C in = 7x22uF (ceramic 206) + x330uf (electrolytic) C out = 6x00uF (ceramic 206) 9//203

2 IRDC3846-PV2 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +2V 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. If operation with external Vcc is required, then R3 should be removed and external Vcc can be applied between Vcc+ and Vcc- pins. 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, R8 should be uninstalled and R9 should be installed instead. External Enable signal can be applied to the board via exposed Enable pad and R00 should be removed for this purpose. Table I. Connections Connection VIN+ VIN- Vout+ Vout- Vcc+ Vcc- Enable PGood Signal Name (+2V) Ground of Vout(+.2V) 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 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 R7. 9//203 2

3 IRDC3846-PV2 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 R7. Gnd Gnd Vo Top View 9//203 3

4 IRDC3846-PV2 FB Vref 6 x 00uF / 206 / 6.3V / Ceramic Capacitor L 250nH WE P SW 24 VCC C00 C0 C02 C03 C04 C05 C06 C07 C08 C3 C4 C5 C2 C30 VDDQ 23 00uF 00uF 00uF 00uF 00uF 00uF 0.uF NC4 C8 C NC NC3 0uF uf 3 IR3846 R2 NC2 VCC 2 VCC R0 R C09 C0 C C6 C7 C8 C9 C20 C2 C22 C23 C24 R4 0K 0K BOOT 4 20 BOOT 5 PGD Enable PGD 9 RT/Sync 6 8 Vp RT/Sy nc Vp 7 7 Vref OCset Vref + C25 + C26 + C27 + C28 + C29 R9 C5 R3 39.2K C7 00pF R6 4.02K S_Ctrl C40 R4 4.02K R3 0 R7 C4 R70 Optional "-bit VID" circuit Single point of connection between Power Ground and Signal ( analog ) Ground Fig. : Schematic of the IRDC3846 evaluation board Vout+ OCSelect pin jumper Optional Pre-Bias test circuit Vout Vo_R_P 0 R6 0 R5 C6 R7 FB Sy nc R0 7.5K SW 0.uF C0 0 R0 Vsns R4 R8 R9 60pF C2 0 C 8.2nF FB 2.7K R R4 Vout_Adj 27 R2 R5 BODE M2 C3 20 JUMPER pF R40 P PGD P 7 x 22uF / 206 / 25V / Ceramic Capacitor 330uF / 25V / Electrolytic Capacitor BOOT U Vsns FB Comp RSo PGND LGND S_Ctrl RS- RS+ NC5 26 D Vcc- R7 4.02K 0 R47 + R R49 VPB - 2 Vout D2 BODE2 JUMPER 3 2 Vsns VCC PG_PU Rt/Sync PG_Pullup PG_PU Vcc+ Agnd R3 0 VCC C9 R K 4.02K R46-R49: 206 pads 0 R46 C7-C80: 0805 / 206 pads P C70 C7 C72 C73 C74 0.uF 22uF 22uF 22uF 22uF C00-C24: 0805 / 206 pads Vo_R_N 0 R8 Vout Vout- PGood C5 Vref C75 C76 C77 C78 C79 C80 + C8 22uF 22uF 22uF 330uF Sy nc Enable Vp Vp 9//203 4

5 IRDC3846-PV2 Schematic for Transient Load set up VCC ExtLoadCtrl 3 2 S3 SW R34 R35 R U2 VS 7 VS 8 IN OUT2 6 N/A OUT 5 GND GND MIC4452/SO8 C30 R38 R39 D3 D4 M IRF672 R36 R37 I-Monitor Vout Vout Vo_R_P R3 C3 R32 C32 R33 C33 Vo_R_N Optional transient load circuit 9//203 5

6 IRDC3846-PV2 Bill of Materials Item Qty Part Reference Value Description Manufacturer Part Number C7 C72 C73 7 C74 C75 C76 22uF 206, 25V, X5R, 0% Murata GRM3CR6E226KE5L C77 2 C6 uf 0603, X5R, 25V, 20% TDK C608X5RE05M 3 C8 0uF 0603, X5R, 0V, 20% TDK C608X5RA06M 4 3 C0 C70 C30 0.uF 0603, 25V, X7R, 0% Murata GRM88R7E04KA0D 5 C 8200pF 0603, 50V, X7R, 0% Murata GRM88R7H822KA0D 6 C2 60pF 0603, 50V, NP0, 5% Murata GRM885CH6JA0D 7 C3 2200pF 0603, 50V, X7R, 0% Murata GRM88R7H222KA0D 8 C7 00pF 0603, 50V, C0G, 5% Murata GRM885CH0JA0D 9 C8 SMD Elecrolytic, Fsize, 330uF 25V, 20% Panasonic EEV-FKE33P 0 L 250nH 250nH, Wurth DCR=0.65mohm Electronics Inc C0 C02 C03 00uF C04 C05 C06 206, 6.3V, X5R, 20% Murata GRM3CR60J07ME39L 2 6 R3 R0 R8 R5 R6 R ,/0W, Jumper Vishay/Dale CRCW Z0EA 3 R9 39.2K 0603,/0W,% Panasonic ERJ-3EKF3922V 4 R 2.7K 0603,/0W,% Panasonic ERJ-3EKF270V 5 R ,/0W,% Panasonic ERJ-3EKF270V 6 4 R3 R4 R6 R K 0603,/0W,% Panasonic ERJ-3EKF402V 7 R ,/0W,% Vishay/Dale CRCW060320R0FKEA 8 2 R46 R ,/4W, Jumper Yageo RC206JR-070RL 9 R , /6W, Jumper Yageo RC0402JR-070RL 20 R K 0603,/0 W,% Panasonic ERJ-3EKF4992V 2 R0 7.5K 0603,/0W,% Panasonic ERJ-3EKF750V 22 2 R0 R 0K 0603,/0 W,% Panasonic ERJ-3EKF002V 23 Jumper PLUG 40 POS DBL Omron ROW STR Electronics Inc. XG8W-404-ND Vout+ RED SCREW TERMIN Keystone Vout- BLACK SCREW TERMIN Electronics Keystone Electronics 26 U IR3846 IR3846 5mm X 7mm International Rectifier IR3846MPBF 9//203 6

7 IRDC3846-PV2 TYPIC OPERATING WAVEFORMS =2.0V, Vo=.2V, Io=0A-35A, Fsw=600kHz, Room Temperature, No air flow Fig. 2: Start up at 35A Load Ch :V in, Ch 2 :V o, Ch 3 :PGood, Ch 4 :Enable Fig. 3: Start up at 35A Load Ch :V in, Ch 2 :V o, Ch 3 :PGood, Ch 4 :V cc Fig. 4: Start up with.08v Pre Bias, 0A Load Ch 2 :V o, Ch 3 :PGood Fig. 5: Output Voltage Ripple, 35A load Ch : V o Fig. 6: Inductor node at 35A load Ch 2 :LX Fig. 7: Short (Hiccup) Recovery Ch 2 :V o, Ch 3 :PGood, Ch 4 :I o 9//203 7

8 TYPIC OPERATING WAVEFORMS =2.0V, Vo=.2V, Io=3.5A-4A, Fsw=600kHz, Room Temperature, No air flow IRDC3846-PV2 Fig. 8: Transient Response, 3.5A to 4A step (2.5A/us) Ch 2 :V o 9//203 8

9 TYPIC OPERATING WAVEFORMS =2.0V, Vo=.2V, Io=24.5A-35.0A, Fsw=600kHz, Room Temperature, No air flow IRDC3846-PV2 Fig. 9: Transient Response, 24.5A to 35A step (2.5A/us) Ch 2 :V o 9//203 9

10 TYPIC OPERATING WAVEFORMS =2.0V, Vo=.2V, Io=0A-35A, Fsw=600kHz, Room Temperature, No air flow IRDC3846-PV2 Fig. 0: Bode Plot at 35A load: Fo = 00.6kHz; Phase Margin = 52.8º; Gain Margin = -7.2dB 9//203 0

11 IRDC3846-PV2 TYPIC OPERATING WAVEFORMS =2.0V, Vo=.2V, Io=0A-35A, Fsw=600kHz, 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 9//203

12 IRDC3846-PV2 THERM IMAGES =2.0V, Vo=.2V, Io=35A, Fsw=600kHz, Room Temperature, No air flow Fig. 3: Thermal Image of the board at 35A load Test point is IR3846: 98.80C Test point 2 is inductor: 72.90C 9//203 2

13 IRDC3846-PV2 THERM IMAGES =2.0V, Vo=.2V, Io=35A, Fsw=600kHz, Room Temperature, LFM = 00 Fig. 4: Thermal Image of the board at 35A load Test point is IR3846: 740C Test point 2 is inductor: 46.90C 9//203 3

14 IRDC3846-PV2 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. 9//203 4