IRDC3831W SupIRBuck TM USER GUIDE FOR IR3831W EVALUATION BOARD DESCRIPTION The IR3831W is a synchronous buck converter, providing a compact, high performance and flexible solution in a small 5mmx6mm Power QFN package. An 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. Key features offered by the IR3831W include programmable soft-start ramp, thermal protection, Power Good, programmable switching frequency, tracking input, enable input, input under-voltage lockout for proper start-up, and pre-bias start-up. This user guide contains the schematic and bill of materials for the IR3831W evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3831W is available in the IR3831W data sheet. BOARD FEATURES • Vin = +12V (13.2V Max) • Vcc= +5V (5.5V Max) • Vout = +0.75V @ 0- ±8A • Fs = 400kHz • L = 0.6uH • Cin= 3x10uF (ceramic 1206) + 330uF (electrolytic) • Cout= 8x22uF (ceramic 0805) 11/05/09 1 IRDC3831W CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum ±8A load should be connected to VOUT+ and VOUT-. The connection diagram is shown in Fig. 1 and inputs and outputs of the board are listed in Table I. IR3831W has two input supplies, one for biasing (Vcc) and the other as input voltage (Vin). Separate supplies should be applied to these inputs. Vcc input should be a well regulated 4.5V-5.5V supply and it would be connected to Vcc+ and Vcc-. If single 12V application is required, connect R7 ( zero Ohm resistor) which enables the on board bias regulator (see schematic). In this case there is no need of external Vcc supply. The output tracks VDDQ input. The value of R14 and R28 can be selected to provide the desired ratio between the output voltage and the tracking input. For proper operation of IR3831W, the voltage at Vp pin should not exceed Vcc. Table I. Connections Connection Signal Name VIN+ Vin (+12V) VIN- Ground of Vin Vcc+ Vcc input Vcc- Ground for Vcc input VOUT- Ground of Vout VOUT+ Vout (+0.75V) Enable Enable VDDQ Tracking Input PGood Power Good Signal LAYOUT The PCB is a 4-layer board. All of layers are 2 Oz. copper. The IR3831W SupIRBuck and all of the passive components are mounted on the top side of the board. Power supply decoupling capacitors, the Bootstrap capacitor and feedback components are located close to IR3831W. The feedback resistors are connected to the output voltage at the point of regulation and are located close to the SupIRBuck. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. 11/05/09 2 IRDC3831W Connection Diagram Vin GND Enable Vp GND VDDQ AGND Vo PGood SS Vcc GND Fig. 1: Connection diagram of IR383xW evaluation boards 11/05/09 3 IRDC3831W Fig. 2: Board layout, top overlay Fig. 3: Board layout, bottom overlay 11/05/09 4 IRDC3831W AGND Plane PGND Plane Single point connection between AGND and PGND. Fig. 4: Board layout, mid-layer I Fig. 5: Board layout, mid-layer II 11/05/09 5 Vcc- PGood 1 1 1 R17 10.0K Vcc+ R28 1.50K VCC C23 10nF Agnd SS C26 22000pF R9 35.7K R1 1.48K C11 560pF 1 1 Vp C10 22000pF 1 7 6 5 4 3 2 Vp 1 R19 7.50k 13 IR3831W R3 N/S R2 6.65K 210 R4 C13 0.1uF VCC PGnd SW Vin 10 11 12 A C24 0.1uF 20 R6 C8 2200pF PGND R10 0 49.9K B R* 0 L1 600nH Vin C28 N/S N/S R7 + C22 22uF Ground and Signal ( “analog” ) Ground N/S C5 10uF 10uF D1 MM3Z5V6B Q1 MMBT3904-TP C15 C34 0.1uF Vcc 1 1 Vin+ Vin+ Vout Vout+ Vout+ Vin- 1 Vout- C14 0.1uFVout1 1 1 1 330uF1 Vin- + C1 22uF 22uF C16 10uF C2 Optional +5V supply for Vcc C32 0.1uF R5 3.30K C36 N/S C17 22uF C3 C4 C20 C19 C18 22uF 22uF 22uF C35 + N/S C21 22uF N/S 0.1uF C27 N/S C6 C7 Single point of connection between Power R12 3.24k 1 Fig. 6: Schematic of the IR3831W evaluation board OCset SS Rt AGnd1 COMP FB Vp U1 C25 N/S 1 14 Enable PGood 8 Boot Vcc 9 R14 1.50K 1 AGnd3 15 R18 1 Enable 1 VDDQ 2 11/05/09 1 Vin IRDC3831W 6 IRDC3831W Bill of Materials Item Quantity Part Reference Value Description Manufacturer Part Number 1 2 3 4 5 6 7 1 3 1 1 5 1 1 C1 C2 C3 C4 C10 C34 C7 C13 C14 C24 C32 C8 C11 330uF 10uF 0.022uF 10uF 0.1uF 2200pF 560pF SMD Elecrolytic, Fsize, 25V, 20% 1206, 16V, X5R, 20% 0603, 16V, X7R, 10% 0805, 10V, X5R, 20% 0603, 25V, X7R, 10% 0603, 50V, NP0, 5% 0603, 50V, NP0, 5% Panasonic TDK Panasonic- ECG Panasonic - ECG Panasonic - ECG Murata Panasonic- ECG EEV-FK1E331P C3216X5R1E106M ECJ-1VB1C223K ECJ-GVB1A106M ECJ-1VB1E104K GRM1885C1H222JA01D ECJ-1VC1H561J 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 8 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 C15 C16 C17 C18 C19 C20 C21 C22 C25 C26 D1 L1 Q1 R5 R18 R4 R6 R9 R12 R17 R19 R10 R1 R2 R14, R28 U1 22uF 10000pF 22000pF MM3Z5V6B 0.6uH MMBT3904/SOT 3.3k 49.9k 210 20 35.7k 3.24k 10.0k 7.5k 0 1.48k 6.65k 1.50k IR3831W 0805, 6.3V, X5R, 20% 0603, 50V, X7R, 10% 0603, 50V, X7R, 10% Zener, 5.6V 11.5x10x4mm, 20%, 1.7mOhm NPN, 40V, 200mA, SOT-23 Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10 W,1% Thick Film, 0603,1/10W,1% Thick Film, 0603,1/10 W,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,1% 8A SupIRBuck, 6mmx5mm Panasonic- ECG Panasonic - ECG Panasonic - ECG Fairchild Delta Fairchild Rohm Rohm Panasonic - ECG Vishey/Dale Rohm Rohm Rohm Rohm Yageo Rohm Rohm Rohm International Rectifier ECJ-2FB0J226M ECJ-1VB1H103K ECJ-1VB1H223K MM3Z5V6B MPL104-0R6IR MMBT3904/SOT MCR03EZPFX3301 MCR03EZPFX4992 ERJ-3EKF2100V CRCW060320R0FKEA MCR03EZPFX3572 MCR03EZPFX3241 MCR03EZPFX1002 MCR03EZPFX7501 RC0603FR-100RL MCR03EZPFX1481 MCR03EZPFX6651 MCR03EZPFX1501 IR3831WMPbF 11/05/09 7 IRDC3831W TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc=5V, Vo=0.75V, Io=0- ±8A, Room Temperature, No Air Flow Fig. 7: Start up at 8A, sourcing current Ch1:PGood, Ch2:Vout, Ch3:SS, Ch4:VDDQ Fig. 8: Start up with Prebias, 0A Load Ch1:PGood, Ch2:Vout, Ch3:SS, Ch4:VDDQ Fig. 9: Inductor node at 8A, sourcing current, Ch3:SW, Ch4:Iout Fig. 10: Inductor node at -3A, sinking current, Ch3:SW , Ch4:Iout Fig. 11: Output Voltage Ripple, 8A, sourcing current, Ch2: Vout Fig. 12: Short (Hiccup) Recovery Ch2:Vout, Ch3:VSS , Ch4:PGood 11/05/09 8 IRDC3831W TYPICAL OPERATING WAVEFORMS Vin=12V, Vcc=5V, Vo=0.75V, Room Temperature, No Air Flow Fig. 13: Tracking 8A, sourcing current, Ch2:Vout, Ch3:VDDQ, Ch4:PGood Fig. 14: Tracking -3A load, sinking current, Ch2:Vout, Ch2: IL, Ch3:VDDQ, Ch4:PGood Fig. 15: Transient Response, 1A/us -0.5A to +0.5A load , Ch1:Vout, Ch3:Io 11/05/09 9 IRDC3831W TYPICAL OPERATING WAVEFORMS Vin=12V, Vcc=5V, Vo=0.75V, Io=+8A, Room Temperature, No Air Flow Fig.16: Bode Plot at 8A load (sourcing current) shows a bandwidth of 59kHz and phase margin of 59 degrees 11/05/09 10 IRDC3831W TYPICAL OPERATING WAVEFORMS Vin=12V, Vo=0.75V, Io=0- +8A, Room Temperature, No Air Flow 89 Efficiency (%) 88 87 86 85 84 83 10 20 30 40 50 60 70 80 90 100 80 90 100 Load Percentage (%) Fig.17: Efficiency versus load current 1.2 1.1 1.0 Power Loss (W) 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 10 20 30 40 50 60 70 Load Percentage(%) Fig.18: Power loss versus load current 11/05/09 11 IRDC3831W THERMAL IMAGES Vin=12V, Vo=0.75V, Io=+8A, Room Temperature, No Air Flow Fig.19: Thermal Image at 8A load Test Point 1: IR3831W, Test Point 2: Inductor 11/05/09 12 IRDC3831W PCB Metal and Components Placement The lead lands (the 11 IC pins) width should be equal to the nominal part lead width. The minimum lead to lead spacing should be ≥ 0.2mm to minimize shorting. Lead land length should be equal to the maximum part lead length + 0.3 mm outboard extension. The outboard extension ensures a large and inspectable toe fillet. The pad lands (the 4 big pads other than the 11 IC pins) length and width should be equal to maximum part pad length and width. However, the minimum metal to metal spacing should be no less than 0.17mm for 2 oz. Copper; no less than 0.1mm for 1 oz. Copper and no less than 0.23mm for 3 oz. Copper. 11/05/09 IRDC3831W Solder Resist It is recommended that the lead lands are Non Solder Mask Defined (NSMD). The solder resist should be pulled away from the metal lead lands by a minimum of 0.025mm to ensure NSMD pads. The land pad should be Solder Mask Defined (SMD), with a minimum overlap of the solder resist onto the copper of 0.05mm to accommodate solder resist mis-alignment. Ensure that the solder resist in between the lead lands and the pad land is ≥ 0.15mm due to the high aspect ratio of the solder resist strip separating the lead lands from the pad land. 11/05/09 IRDC3831W Stencil Design • • The Stencil apertures for the lead lands should be approximately 80% of the area of the lead lads. Reducing the amount of solder deposited will minimize the occurrences of lead shorts. If too much solder is deposited on the center pad the part will float and the lead lands will be open. The maximum length and width of the land pad stencil aperture should be equal to the solder resist opening minus an annular 0.2mm pull back to decrease the incidence of shorting the center land to the lead lands when the part is pushed into the solder paste. 11/05/09 IRDC3831W BOTTOM VIEW 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 Consumer market. Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 11/07 11/05/09