IRDC3831 Datasheet, PDF (2/16 Pages) International Rectifier – USER GUIDE FOR IR3831 EVALUATION BOARD

IRDC3831
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.
IR3831 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 IR3831, the voltage at Vp pin
should not exceed Vcc.
Table I. Connections
Connection
VIN+
VIN-
Vcc+
Vcc-
VOUT-
VOUT+
Enable
V_DDQ
PGood
Signal Name
V_in (+12V)
Ground of V_in
Vcc input
Ground for Vcc input
Ground of V_out
V_out (+0.75V)
Enable
Tracking Input
Power Good Signal
LAYOUT
The PCB is a 4-layer board. All of layers are 2 Oz. copper. The IR3831 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 IR3831. 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.
02/10/09
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