IRDC3894

IRDC3894-P1V2 SupIRBuck TM USER GUIDE FOR IR3894 EVALUATION BOARD 1.2Vout DESCRIPTION The IR3894 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 IR3894 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 IR3894 evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3894 is available in the IR3894 data sheet. BOARD FEATURES • Vin = +12V (+ 13.2V Max) •Vout = +1.2V @ 0- 12A • Fs=600kHz • L= 0.51uH • Cin= 4x10uF (ceramic 1206) + 1X330uF (electrolytic) • Cout=8x22uF (ceramic 0805) 12/5/2012 1 IRDC3894-P1V2 CONNECTIONS AND OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 12A load should be connected to VOUT+ and VOUT-. The input and output connections of the board are listed in Table I. IR3894 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 IR3894 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 IR3894. 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. 12/5/2012 2 IRDC3894-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 12/5/2012 3 IRDC3894-P1V2 Fig. 2: Board Layout-Top Layer Single point connection between Analog Gnd and PGnd Fig. 3: Board Layout-Bottom Layer 12/5/2012 4 IRDC3894-P1V2 Fig. 4: Board Layout-Mid Layer 1 Fig. 5: Board Layout-Mid Layer 2 12/5/2012 5 SY NC PGood N/S R28 Vcc R17 49.9K N/A C10 R14 0 VDDQ R9 10nF C26 S_Ctrl 39.2K 1.82K R1 220pF C11 C12 100pF 1 0 R13 6 16 5 4 3 1 C37 N/S IR3894 R7 (N/S) SW PVin U1 C8 R2 2200pF 0 R50 PGND 4.02K 11 12 C7 0.1uF 13 R10 0 R3 2.87K 100 R4 PGnd C32 1.0uF 49.9K A 0.1uF C24 NS C25 R6 20 Vsns B 1 VCC R29 R12 2.87K 4.02K R11 L1 0.51uH N/S R15 0 C34 C33 C30 22uF 22uF N/S C28 N/S + C36 N/S C29 N/S + C35 N/S C27 N/S C6 N/S C9 N/S Fig. 6: Schematic of the IR3894 evaluation board C21 C23 N/S 2.2uF VCC S_Ctrl Vp Rt_Sy nc AGnd COMP FB 7.5k R19 2 VREF 1 15 Enable Vcc/LDO_OUT 10 1 1 9 Vin PGood 7 1 1 Vsns 8 R21 N/S 1 14 Boot AGND 17 VREF 1 R18 1 12/5/2012 1 Enable C20 22uF C5 10uF C19 22uF C4 10uF C3 C18 22uF C16 22uF C2 10uF C17 22uF 10uF C1 + 1 1 C15 C14 22uF 0.1uF1 330uF/25V 1 Vout- Vout+(1.2Vout) Vin- Vin+ IRDC3894-P1V2 6 IRDC3894-P1V2 Bill of Materials Item Qty Part Reference Value 1 C1 330uF 2 4 C2 C3 C4 C5 10uF 1206, 25V, X5R, 20% TDK C3216X5R1E106M 3 3 C7 C14 C24 0.1uF 0603, 25V, X7R, 10% 0603,50V,NP0, 5% Murata GRM188R71E104KA01B Murata GRM1885C1H101JA01D 0603,50V,X7R,10% 0603, 50V, COG, 5% Murata Murata GRM188R71H222KA01B GRM1885C1H2201JA01D 1 Description Manufacturer SMD Electrolytic F size 25V 20% Panasonic Part Number EEV-FK1E331P 4 1 C12 100pF 5 1 C8 2200pF 6 1 C11 220pF 7 8 C15 C16 C17 C18 C19 C20 C33 C34 22uF TDK C2012X5R0J226M 8 1 C23 2.2uF 0603, 16V, X5R, 20% TDK C1608X5R1C225M 0805, 6.3V, X5R, 20% 9 1 C26 10nF 0603, 25V, X7R, 10% Murata GRM188R71E103KA01J 10 1 C32 1.0uF 0603, 25V, X5R, 10% Murata GRM188R61E105KA12D 11 1 L1 0.51uH Vitec 59PR9876N Panasonic ERJ-3EKF1821V Panasonic ERJ-3EKF4021V 12 1 R1 1.82k SMD 11.0x7.2x7.5mm,0.29mΩ Thick Film, 0603,1/10W,1% 13 2 R2 R11 4.02k Thick Film, 0603,1/10W,1% 14 2 R3 R12 2.87k Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF2871V 15 1 R4 100 Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF1000V 16 1 R6 20 Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF20R0V Panasonic ERJ-3EKF3922V Panasonic ERJ-3GEY0R00V 17 1 R9 39.2k Thick Film, 0603,1/10W,1% 18 5 R10 R13 R14 R15 R50 0 Thick Film, 0603,1/10W 19 2 R17 R18 49.9k Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF4992V 20 1 R19 7.5k Thick Film, 0603,1/10W,1% Panasonic ERJ-3EKF7551V 21 1 U1 IR3894 PQFN 5x6mm IR IR3894MPBF 12/5/2012 7 IRDC3894-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-12A, Room Temperature, no airflow Fig. 7: Start up at 12A 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 12A load Ch1:Switch Node 12/5/2012 Fig. 8: Start up at 12A Load Ch1:Vout, Ch2:Vin, Ch3: PGood,Ch4:Vcc Fig. 10: Output Voltage Ripple, 12A load Ch1: Vout , Fig. 12: Short circuit (Hiccup) Recovery Ch1:Vout , Ch4:Iout 8 IRDC3894-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-12A, Room Temperature, no air flow Fig. 13: Transient Response, 6A to 12A step @2.5A/usec slew rate Ch4-Iout Ch1:Vout 12/5/2012 9 IRDC3894-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-12A, Room Temperature Fig. 14: Bode Plot at 12A load shows a bandwidth of 99.9kHz and phase margin of 55.2º 12/5/2012 10 IRDC3894-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-12A, 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 12/5/2012 11 IRDC3894-P1V2 TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vo=1.2V, Io=0-12A, Room Temperature, no air flow Fig.17: Efficiency versus load current Fig.18: Power loss versus load current 12/5/2012 12 IRDC3894-P1V2 THERMAL IMAGES Vin=12.0V, Vo=1.2V, Io=0-12A, Room Temperature, No Air flow Fig. 19: Thermal Image of the board at 12A load Test point 1 is IR3894 Test point 2 is inductor 12/5/2012 13 IRDC3894-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 12/5/2012 14