IRDC3895-P1V2 SupIRBuck TM USER GUIDE FOR IR3895 EVALUATION BOARD 1.2Vout DESCRIPTION The IR3895 is a synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mm X 6 mm Power QFN package. Key features offered by the IR3895 include internal Digital Soft Start/Soft Stop, precision 0.5Vreference 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, smart internal LDO and pre-bias start-up. 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 and the current limit is thermally compensated. This user guide contains the schematic and bill of materials for the IR3895 evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3895 is available in the IR3895 data sheet. BOARD FEATURES • Vin = +12V (+ 13.2V Max) •Vout = +1.2V @ 0- 16A • Fs=600kHz • L= 0.4uH • Cin= 5x10uF (ceramic 1206) + 1X330uF (electrolytic) • Cout=6x47uF (ceramic 0805) 12/22/2011 1 IRDC3895-P1V2 CONNECTIONS AND OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 16A load should be connected to VOUT+ and VOUT-. The input and output connections of the board are listed in Table I. IR3895 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc is required, then R15 can be removed and external Vcc can be applied between Vcc+ and Vcc- pins. Vin pin and Vcc/LDOout pins should be shorted together for external Vcc operation (use zero ohm resistor for R29). The output can track voltage at the Vp pin. For this purpose, Vref pin is to be connected to ground (use zero ohm resistor for R21). The value of R14 and R28 can be selected to provide the desired tracking ratio between output voltage and the tracking input. Table I. Connections Connection Signal Name VIN+ Vin (+12V) VIN- Ground of Vin Vout+ Vout(+1.2V) Vout- Ground for Vout Vcc+ Vcc/ LDO_out Pin Vcc- Ground for Vcc input Enable Enable PGood Power Good Signal Gnd Analog ground LAYOUT The PCB is a 4-layer board (2.23”x2”) using FR4 material. All layers use 2 Oz. copper. The PCB thickness is 0.062”. The IR3895 and other major power components are mounted on the top side of the board. Power supply decoupling capacitors, the bootstrap capacitor and feedback components are located close to IR3895. The feedback resistors are connected to the output at the point of regulation and are located close to the SupIRBuck IC. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. 12/22/2011 2 IRDC3895-P1V2 Vin Gnd Gnd Vout Enable Top View VDDQ Vref Sync PGood AGnd S_Ctrl Vsns Vcc+ Vcc- Bottom View Fig. 1: Connection Diagram of IR3895/94 Evaluation Boards 12/22/2011 3 IRDC3895-P1V2 Fig. 2: Board Layout-Top Layer Single point connection between Analog Gnd and PGnd Fig. 3: Board Layout-Bottom Layer 12/22/2011 4 IRDC3895-P1V2 Fig. 4: Board Layout-Mid Layer 1 Fig. 5: Board Layout-Mid Layer 2 12/22/2011 5 Fig. 6: Schematic of the IR3895 evaluation board IRDC3895-P1V2 12/22/2011 6 IRDC3895-P1V2 Bill of Materials Item Qty Part Reference Value 1 1 C1 330uF 2 5 C2 C3 C4 C5 C6 10uF 3 3 C7 C14 C24 0.1uF 4 1 C12 1nF 5 1 C8 3300pF 6 1 C11 220pF 7 6 C15 C16 C17 C18 C19 C20 47uF 8 1 C23 2.2uF 9 1 C26 10nF 10 1 C32 1.0uF 111 1 L1 0.4uH 12 13 14 15 16 17 1 2 2 1 1 1 R1 R2 R11 R3 R12 R4 R6 R9 1.78k 4.02k 2.87k 100 20 39.2k 18 5 R10 R13 R14 R15 R50 0 19 2 R17 R18 49.9k 20 1 R19 7.5k 21 1 U1 IR3895 12/22/2011 Description Manufacturer SMD Electrolytic F size 25V 20% Panasonic 1206, 25V, X5R, 20% Part Number EEV-FK1E331P TDK C3216X5R1E106M Murata GRM188R71E104KA01B Murata GRM1885C1E102JA01D 0603,50V,X7R,10% Murata GRM188R71H332KA01B 0603, 50V, COG, 5% Murata GRM1885C1H221JA01D TDK C2012X5R0J476M TDK C1608X5R1C475M Murata GRM188R71E103KA01J Murata GRM188R61E105KA12D Vitec 59PR9875N Panasonic ERJ-3EKF17801V Panasonic ERJ-3EKF4021V Panasonic ERJ-3EKF2871V Panasonic ERJ-3EKF1000V Panasonic ERJ-3EKF20R0V Panasonic ERJ-3EKF3922V Panasonic ERJ-3GEY0R00V Panasonic ERJ-3EKF4992V Panasonic ERJ-3EKF7551V IR IR3895MPBF 0603, 25V, X7R, 10% 0603, 25V, COG, 5% 0805, 6.3V, X5R, 20% 0603, 16V, X5R, 20% 0603, 25V, X7R, 10% 0603, 25V, X5R, 10% SMD 11.0x7.2x7.5mm,0.29mΩ Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% PQFN 5x6mm 7 IRDC3895-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-16A, Room Temperature, no airflow Fig. 7: Start up at 16A Load Ch1:Vout, Ch2:Vin, Ch3:PGood,Ch4:Enable Fig. 9: Start up with Pre Bias , 0A Load, Ch1:Vo Fig. 11: Inductor node at 16A load Ch1:Switch Node 12/22/2011 Fig. 8: Start up at 16A Load Ch1:Vout, Ch2:Vin, Ch3: PGood,Ch4:Vcc Fig. 10: Output Voltage Ripple, 16A load Ch1: Vout , Fig. 12: Short circuit (Hiccup) Recovery Ch1:Vout , Ch4:Iout 8 IRDC3895-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-16A, Room Temperature, no air flow Fig. 13: Transient Response, 8A to 16A step @2.5A/usec slew rate Ch4-Iout Ch1:Vout 12/22/2011 9 IRDC3895-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-16A, Room Temperature Fig. 14: Bode Plot at 16A load shows a bandwidth of 95.2kHz and phase margin of 54.5º 12/22/2011 10 IRDC3895-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-16A, Room Temperature, no air flow Fig (15) Soft start and soft stop using S_Ctrl pin Fig (16) Feed Forward for Vin change from 6.8 to 16V and back to 6.8V Ch1-Vout Ch4-Vin 12/22/2011 11 IRDC3895-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-16A, Room Temperature, no air flow Fig.17: Efficiency versus load current Fig.18: Power loss versus load current 12/22/2011 12 IRDC3895-P1V2 THERMAL IMAGES Vin=12.0V, Vo=1.2V, Io=0-16A, Room Temperature, No Air flow Fig. 19: Thermal Image of the board at 16A load Test point 1 is IR3895 Test point 2 is inductor 12/22/2011 13 IRDC3895-P1V2 PACKAGE INFORMATION DIM A A1 b b1 c D E e e1 e2 MILIMITERS MIN MAX 0.800 1.000 0.000 0.050 0.375 0.475 0.250 0.350 0.203 REF. 5.000 BASIC 6.000 BASIC 1.033 BASIC 0.650 BASIC 0.852 BASIC INCHES MIN MAX 0.0315 0.0394 0.0000 0.0020 0.1477 0.1871 0.0098 0.1379 0.008 REF. 1.969 BASIC 2.362 BASIC 0.0407 BASIC 0.0256 BASIC 0.0335 BASIC DIM L M N O P Q R S t1, t2, t3 t4 t5 MILIMITERS MIN MAX 0.350 0.450 2.441 2.541 0.703 0.803 2.079 2.179 3.242 3.342 1.265 1.365 2.644 2.744 1.500 1.600 0.401 BASIC 1.153 BASIC 0.727 BASIC INCHES MIN MAX 0.0138 0.0177 0.0961 0.1000 0.0277 0.0316 0.0819 0.0858 0.1276 0.1316 0.0498 0.0537 0.1041 0.1080 0.0591 0.0630 0.016 BACIS 0.045 BASIC 0.0286 BASIC Figure 20: Package Dimensions IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 This product has been designed and qualified for the Industrial market Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 12/11 12/22/2011 14