IRDC3843W SupIRBuck TM USER GUIDE FOR IR3843W EVALUATION BOARD DESCRIPTION The IR3843W 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 IR3843W include programmable soft-start ramp, precision 0.7V reference voltage, Power Good, thermal protection, programmable switching frequency, Sequence 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 IR3843W evaluation board. The guide describes operation and use of the evaluation board itself. Detailed application information for IR3843W is available in the IR3843W data sheet. BOARD FEATURES • Vin = +12V (13.2V Max) • Vcc=+5V (5.5V Max) • Vout = +1.8V @ 0- 2A • Fs=600kHz • L= 3.3uH • Cin= 1x10uF (ceramic 1206) + 330uF (electrolytic) • Cout= 2x22uF (ceramic 0805) 10/27/2009 1 IRDC3843W CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum 2A 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. IR3843W 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 can track a sequencing input at the start-up. For sequencing application, R16 should be removed and the external sequencing source should be applied between Seq. and Agnd. 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 IR3843W, the voltage at Seq. 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 (+1.8V) Enable Enable Seq. Sequence Input P_Good Power Good Signal LAYOUT The PCB is a 4-layer board. All of layers are 2 Oz. copper. The IR3843W 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 IR3843W. 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. 10/27/2009 2 IRDC3843W Connection Diagram Vin GND Enable GND Seq AGND Vo PGood SS Vcc GND Fig. 1: Connection diagram of IR384xW evaluation boards 10/27/2009 3 IRDC3843W Fig. 2: Board layout, top overlay Fig. 3: Board layout, bottom overlay (rear view) 10/27/2009 4 IRDC3843W PGND Plane Single point connection between AGND and PGND. AGND Plane Fig. 4: Board layout, mid-layer I. Fig. 5: Board layout, mid-layer II. 10/27/2009 5 Vcc- PGood 1 1 R17 10K Vcc+ R14 N/S 1 VCC R28 N/S R16 0 C11 180pF Agnd C26 R1 2.74k 8.2nF R9 23.7K 1 SS C10 0.1uF 7 6 5 4 3 2 Seq1 R19 7.5k 1 IR3843W 4.99K R2 R3 3.16K ohm 158ohm R4 C13 0.1uF VCC PGnd SW Vin 49.9K R18 10 11 12 PGND A B 0 R* L1 3.3uH IHLP2525EZ-01 3.3uH Vin C30 N/S R7 N/S C29 N/S C7 0.1uF Ground and Signal ( “analog” ) Ground Single point of connection between Power R6 20 C8 2200pF R12 1.54K 0.1uF C24 1 1 Fig. 6: Schematic of the IR3843W evaluation board OCset SS Rt AGnd COMP FB Seq U1 C25 N/S 13 Boot 14 En PGood 8 Vcc 9 AGnd1 15 1 Enable 1 VCC 1 Seq. C21 N/S C28 N/S C19 N/S C18 N/S C4 N/S C17 N/S C3 N/S + + C36 N/S Optional +5V supply for Vcc D1 MM3Z5V6B Q1 MMBT3904-TP C35 N/S 2X22uF,0805,6.3V C20 N/S C5 N/S C32 0.1uF R5 3.30K C22 N/S C27 N/S C6 N/S 2 10/27/2009 1 Vcc C16 22uF C2 10uF C34 1uF C15 22uF + C1 330uF 1 1 1 1 1 1 1 1 C14 0.1uF Vout Vin Vout- Vout- Vout+ Vout+ Vin- Vin- Vin+ Vin+ IRDC3843W 6 IRDC3843W Bill of Materials Item Quantity Part Reference Value Description Manufacturer Part Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 1 1 6 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 C2 C1 C7 C14 C24 C10 C13 C32 C8 C11 C15 C16 C26 L1 R1 R2 R3 R4 R6 R9 R16 R12 R17 R18 R19 R5 C34 D1 10uF 330uF 0.1uF 2200pF 180pF 22uF 8200pF 3.3uH 2.74k 4.99k 3.16k 158 20 23.7K 0 1.54K 10K 49.9k 7.5k 3.3k 1uF MM3Z5V6B 1206,16V, X7R, 20% SMD Elecrolytic, Fsize, 25V, 20% 0603, 25V, X7R, 10% 2200pF,0603,50V,X7R 50V, 0603, NP0, 5% 0805, 6.3V, X5R, 20% 0603, 50V, X7R, 10% 6.9x6.5x5mm, 8A,20% 0603,1/10W,1% 0603,1/10W,1% 0603,1/10W,1% 0603,1/10W,1% 0603,1/10 W,1% 0603,1/10W,1% 0603,1/10 W,5% 0603,1/10 W,1% 0603,1/10 W,1% 0603,1/10 W,1% 0603,1/10W,1% 0603,1/10W,1% 1uF, 10V, X5R,0805 Zener,5.6V Panasonic - ECG Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Vishay/Dale Rohm Rohm Rohm Panasonic Vishay/Dale Rohm Vishay/Dale Rohm Rohm Rohm Rohm Rohm Panasonic Fairchild ECJ-3YX1C106K EEV-FK1E331P ECJ-1VB1E104K ECJ-1VB1H222K ECJ-1VC1H181J ECJ-2FB0J226M ECJ-1VB1H822K IHLP2525EZ-01 3.3uH MCR03EZPFX2741 MCR03EZPFX4991 MCR03EZPFX3161 ERJ-3EKF1580V CRCW060320R0FKEA MCR03EZPFX2372 CRCW06030000Z0EA MCR03EZPFX1541 MCR03EZPFX1002 MCR03EZPFX4992 MCR03EZPFX7501 MCR03EZPFX3301 ECJ-2FB1C105K MM3Z5V6B 23 24 1 1 Q1 U1 MMBT3904/SOT IR3843W NPN, 200mA, 40V, SOT23 2A SupIRBuck. PQFN 5x6mm Fairchild International Rectifier MMBT3904/SOT IR3843WMPbF 10/27/2009 7 IRDC3843W TYPICAL OPERATING WAVEFORMS Vin=12.0V, Vcc=5V, Vo=1.8V, Io=0-2A, Room Temperature, No Air Flow Fig. 17. Start up at 2A Load Ch1:Vin, Ch2:Vo, Ch3:Vss, Ch4:Enable Fig. 18. Start up at 2A Load, Ch1:Vin, Ch2:Vo, Ch3:Vss, Ch4:VPGood Fig. 19. Start up with 1.62V Pre Bias, 0A Load, Ch2:Vo, Ch3:VSS Fig. 20. Output Voltage Ripple, 2A load Ch2: Vo Fig. 21. Inductor node at 2A load Ch2:LX Fig. 22. Short (Hiccup) Recovery Ch2:Vo , Ch3:VSS 10/27/2009 8 IRDC3843W TYPICAL OPERATING WAVEFORMS Vin=12V, Vcc=5V, Vo=1.8V, Io=0-2A, Room Temperature, No Air Flow Fig. 23. Transient Response, 1A to 2A step 2.5A/s Ch1:Vo, Ch4:Io 10/27/2009 9 IRDC3843W TYPICAL OPERATING WAVEFORMS Vin=12V, Vcc=5V, Vo=1.8V, Io=2A, Room Temperature, No Air Flow Fig. 24. Bode Plot at 2A load shows a bandwidth of 85.54kHz and phase margin of 55.509 degrees 10/27/2009 10 IRDC3843W TYPICAL OPERATING WAVEFORMS Vin=12V, Vo=1.8V, Io=0- 2A, Room Temperature, No Air Flow 93 91 89 Efficiency (%) 87 85 83 81 79 77 75 10 20 30 40 50 60 70 80 90 100 Load Percentage (%) Fig.15: Efficiency versus load current 0.45 0.4 Power Loss (W) 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 10 20 30 40 50 60 70 80 90 100 Load Percentage (%) Fig.16: Power loss versus load current 10/27/2009 11 IRDC3843W THERMAL IMAGES Vin=12V, Vo=1.8V, Io=2A, Room Temperature, No Air Flow Fig. 17: Thermal Image at 2A load Test points 1 and 2 are IR3843W and inductor, respectively. 10/27/2009 12 IRDC3843W Simultaneous Tracking at Power Up and Power Down Vin=12V, Vo=1.8V, Io=2A, Room Temperature, No Air Flow In order to run the IR3843W in the simultaneous tracking mode, the following steps should be taken: - Remove R16 from the board. - Set the value of R14 and R28 as R2 (4.99K) and R3 (3.16K), respectively. - Connect the controlling input across SEQ and AGND test points on the board. This voltage should be at least 1.15 time greater than Vo. For the following test results a 0-3.3V source is applied to SEQ input. - The controlling input should be applied after the SS pin is clamped to 3.0V. Fig. 18: Simultaneous Tracking a 3.3V input at power-up and shut-down Ch2: Vout Ch3:SS Ch4: Seq 10/27/2009 13 IRDC3843W 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. 10/27/2009 IRDC3843W 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. 10/27/2009 IRDC3843W 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. 10/27/2009 IRDC3843W 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 10/27/2009