IRDC3823-P1V2 TM SupIRBuck USER GUIDE FOR IRDC3823 EVALUATION BOARD 1.2Vout DESCRIPTION Output over-current protection function is The IR3823 is a synchronous buck implemented by sensing the voltage developed converter, providing a compact, high across the on-resistance of the synchronous performance and flexible solution in a small MOSFET for optimum cost and performance 3.5mm X 3.5 mm Power QFN package. and the current limit is thermally compensated. Key features offered by the IR3823 include This user guide contains the schematic and bill selectable Digital Soft Start, precision of materials for the IRDC3823 evaluation board. 0.6Vreference voltage, Power Good, The guide describes operation and use of the thermal protection, programmable switching evaluation board itself. Detailed application frequency, Enable input, input under-voltage information for IR3823 is available in the lockout for proper start-up, enhanced line/ IR3823 data sheet. load regulation with feed forward, external frequency synchronization with smooth clocking, internal LDO and pre-bias start-up. BOARD FEATURES V = +12V (+ 13.2V Max) in V = +1.2V 0- 3A out F =1000kHz s L= 1.0uH (4.0mm X 4.0mm X 2.1mm, DCR=10.8m ) C = 2x10uF (25V, ceramic 1206) + 1X100uF (25V, electrolytic) in C =1x22uF (6.3V, ceramic 0805) out 5/7/2013 1IRDC3823-P1V2 CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 3A load should be connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I. IR3823 has only one input supply and internal LDO generates Vcc from Vin. If operation with an external Vcc is required, remove R7 and solder a zero ohm resistor for R5. Then an external Vcc can be applied between Vcc+ and Vcc- pins. Vin pin and Vcc/LDO Out pins should be shorted together for the external Vcc operation. 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 Sync Synchronization Gnd Analog ground Vcc: SS time = 1.5m sec SS Select Float: SS time = 3m sec (Soft-start Selection) Gnd: SS time = 6 m sec LAYOUT The PCB is a 2.6x 2.2 4-layer board using FR4 material. All layers use 2 Oz. copper. The PCB thickness is 0.062. The IR3823 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 IR3823. 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. 5/7/2013 2