IRDC3846-P1V2 SupIRBuck TM USER GUIDE FOR IR3846 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 IR3846 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 (+ 13.2V Max) • Vout = +1.2V @ 0-35A • Fs= 400kHz • L= 0.23uH • Cin= 7x22uF (ceramic 1206) + 1x330uF* (electrolytic) • Cout= 18x100uF (ceramic 0805) * The 330uF input capacitor is placed for damping the parasitic inductance of bench power supply wires. It is not required for the POL applications where input is delivered with power planes. 10/7/2013 Confidential 1 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice 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. 10/7/2013 Confidential 2 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice 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 10/7/2013 Confidential 3 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL Agnd 1 Vcc- 1 Vcc+ 1 VCC 1 Enable C19 N/S 0 R3 PVin C5 N/S R16 6.98k R9 60.4k OCset RT/Sy nc Enable BOOT NC2 NC1 PVin 68pF C12 R114 N/S 7 6 5 4 3 2 1 U1 Confidential C14 N/S C13 2200pF 0 R10 C75 22uF R15 20 R18 0 NC3 Vref Vp PGD Vin VCC C16 N/S 0 R116 R71 R70 PVin Vin L1 R110 10k JUMPER 3 BODE2 C6 1uF 330uF + C81 0 R115 0 N/S R4 C8 10uF C80 N/S N/S 0 R118 N/S R117 17 Vref 18 19 PGD 20 Vin SW C79 N/S C17 100pF VCC C78 N/S 21 VCC 22 23 24 BODE1 JUMPER 2 R19 N/S S_Ctrl SW C77 22uF NC4 C76 22uF 1 C15 N/S Vout Vp R111 N/S 6 5 4 3 2 1 6 5 4 3 2 1 Vo_R_N Vo_R_P R113 N/S R112 N/S VDDQ 0.23uH N/S R49 N/S R48 0 R47 0 R46 + C125 N/S + C126 N/S + C127 N/S + C128 N/S N/S N/S N/S N/S N/S C122 C123 C124 + C129 N/S C119 C120 C121 100uF 100uF 100uF 100uF 100uF 100uF N/S C109 C110 C111 C116 C117 C118 0.1uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF C100 C101 C102 C103 C104 C105 C106 C107 C108 C113 C114 C115 C112 Vin- Vin+ Fig. 1: Schematic of the IR3846 evaluation board 6.98k R13 R12 196 Ohm C11 3.9nF IR3846 0.1uF C10 BOOT C74 22uF 26 NC5 C73 22uF 1 C72 22uF 8.06k R11 C71 22uF RT/Sy nc BOOT 6.98k R14 R17 6.98k R101 7.5k R100 49.9k C70 0.1uF FB 1 PVin VCC Vin FB Comp 10 Vsns 8 Vsns 9 FB RSo 11 PGND 12 LGND 13 RS15 S_Ctrl 14 1 RS+ 16 PG_PU 10/7/2013 1 Vin 0.1uF C130 6 5 4 3 2 1 6 5 4 3 2 1 Vout- Vout+ Vout IRDC3846-P1V2 4 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 Bill of Materials Item Qty Part Reference Value Description Manufacturer Part Number C71 C72 C73 1 7 C74 C75 C76 22uF 1206, 25V, X5R, 10% Murata GRM31CR61E226KE15L C77 C6 1uF 0603, X5R, 25V, 20% TDK 2 1 C1608X5R1E105M080AC C8 10uF 0603, X5R, 10V, 20% TDK 3 1 C1608X5R1A106M080AC 4 3 C10 C70 C100 0.1uF 0603, 25V, X7R, 10% Murata GRM188R71E104KA01D 5 1 C11 3900pF 0603, 50V, X7R, 10% Murata GRM188R71H392KA01D 6 1 C12 68pF 0603, 50V, NP0, 5% Murata GRM1885C1H680JA01D 7 1 C13 2200pF 0603, 50V, X7R, 10% Murata GRM188R71H222KA01D 8 1 C17 100pF 0603, 50V, NP0, 5% Murata GRM1885C1H101JA01D SMD Elecrolytic, Fsize, 9 1 C81 330uF Panasonic EEV-FK1E331P 25V, 20% 45A Isat., 0.29m Ohm, 10 1 L1 0.23uH Coiltronics FP1107R1-R23-R 7.2x11.0x7.5mm C101 C102 C103 C104 C105 C106 C107 C108 C109 11 18 100uF 0805, 4V, X5R, 20% Murata GRM21BR60G107M C110 C111 C112 C113 C114 C115 C116 C117 C118 R3 R10 R18 12 6 0 0603,1/10W, Jumper Vishay/Dale CRCW06030000Z0EA R115 R116 R118 13 1 R9 60.4k 0603,1/10W,1% Panasonic ERJ-3EKF6042V 14 1 R11 8.06k 0603,1/10W,1% Panasonic ERJ-3EKF8061V 15 1 R12 196 0603,1/10W,1% Panasonic ERJ-3EKF1960V R13 R14 R16 16 4 6.98k 0603,1/10W,1% Panasonic ERJ-3EKF6981V R17 17 1 R15 20 0603,1/10W,1% Vishay/Dale CRCW060320R0FKEA 18 2 R46 R47 0 1206,1/4W, Jumper Yageo RC1206JR-070RL 19 1 R71 0 0402, 1/16W, Jumper Yageo RC0402JR-070RL 20 1 R100 49.9k 0603,1/10 W,1% Panasonic ERJ-3EKF4992V 21 1 R101 7.5k 0603,1/10W,1% Panasonic ERJ-3EKF7501V 22 1 R110 10k 0603,1/10 W,1% Panasonic ERJ-3EKF1002V International 23 1 U1 IR3846 IR3846 5mm X 7mm IR3846MPBF Rectifier 10/7/2013 Confidential 5 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow Fig. 2: Start up at 35A load Ch1:Vin, Ch2:Vout, Ch3:PGood, Ch4:Enable Fig. 3: Start up at 35A load Ch1:Vin, Ch2:Vout, Ch3:PGood, Ch4:Vcc Fig. 4: Start up with 1.0V pre bias, 0A load Ch2:Vout, Ch3:PGood, Ch4:Enable Fig. 5: Output voltage ripple, 35A load Ch2: Vout Fig. 7: Short (Hiccup) recovery Ch2:Vout, Ch3:PGood Fig. 6: Inductor node at 35A load Ch3:SW Node 10/7/2013 Confidential 6 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow Fig. 8: Transient response, 0A to 10A Iout at 11.31A/us raising/ 10.34A/us falling slew rates. Ch1:Vimonitor (20.45mV/A)*, Ch2:Vout *Vimonitor is the voltage measured across a current sense resistor in series with the step load at a 20.45mV/A ratio. 10/7/2013 Confidential 7 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow Fig. 9: Transient response, 25A* to 35A Iout at 14.06A/us raising/ 10.01A/us falling slew rates. Ch1:Vimonitor (20.45mV/A)**, Ch2:Vout * An additional constant 25 A load is provided by the electronic load; the figures above show the 10A load step part. ** Vimonitor is the voltage measured across a current sense resistor in series with the step load at a 20.45mV/A ratio. 10/7/2013 Confidential 8 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow 60 200 150 40 20 50 0 TR2/° TR1/dB 100 0 -50 -20 -100 -40 -60 -150 103 104 105 -200 f/Hz TR1: Mag(Gain) TR2: Unwrapped Phase(Gain) Fig. 10: Bode Plot at 35A load: Fc = 89.37kHz; Phase Margin = 48.76º. 10/7/2013 Confidential 9 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow Fig.11: Efficiency versus load current Fig.12: Power loss versus load current 10/7/2013 Confidential 10 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL IRDC3846-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow Fig. 13: Thermal Image of the board at 35A load IR3846: 97.31 0C Inductor: 75 .120C Ambient: 28.29 0C 10/7/2013 Confidential 11 This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results of the continuing evaluation, this board can evolve and change without notice AL