IRDC3820A Infineon

IRDC3820A TM SupIRBuck USER GUIDE FOR IR3820A EVALUATION BOARD DESCRIPTION An output over-current protection function is The IR3820A 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 rectifier MOSFET for optimum cost and 5mmx6mm Power QFN package. performance. Key features offered by the IR3820A include This user guide contains the schematic and bill programmable soft-start ramp, precision of materials for the IR3820A evaluation board. 0.6V reference voltage, programmable The guide describes operation and use of the Power Good, thermal protection, fixed evaluation board itself. Detailed application 300kHz switching frequency requiring no information for the IR3820A is available in the external component, input under-voltage IR3820A data sheet. lockout for proper start-up, and pre-bias start-up. BOARD FEATURES V = +12V (13.2V Max) in V = +1.8V 0- 14A out L= 1.0uH C = 3x10uF (ceramic 1206) + 1x330uF (Electrolytic) in C = 6x22uF (ceramic 0805) out Rev 0.0 1 01/07/2008IRDC3820A CONNECTIONS and OPERATING INSTRUCTIONS A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum 14A 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. IR3820A has two input supplies, one for biasing (Vcc) and the other as input voltage (Vin). These inputs are connected on the board with a zero ohm resistor (R15). Separate supplies can be applied to these inputs. Vcc input cannot be connected unless R15 is removed. Vcc input should be a well regulated 5V-12V supply and it would be connected to Vcc+ and Vcc-. Table I. Connections Connection Signal Name VIN+ V (+12V) in VIN- Ground of V in Vcc+ Optional Vcc input Vcc- Ground for Optional Vcc input VOUT- Ground of V out VOUT+ V (+1.8V) out P Good Power Good Signal LAYOUT The PCB is a 4-layer board. All of layers are 2 Oz. copper. The SupIRBuck and all of the passive components are mounted on the top side of the board. Power supply decoupling capacitors, the charge-pump capacitor and feedback components are located close to the IR3820A. The feedback resistors are connected to the output voltage at the point of regulation and are located close to the SupIRBuck. The input and output energy storage capacitors and the power inductor are located on top side of the board, these are connected to IR3820A through vias. To improve efficiency, the circuit board is designed to minimize the length of the on-board power ground current path. Rev 0.0 2 01/07/2008