IRDC3899-P1V2
9/18/2012
2
A well reg12V input supply should be connected to VIN+ and VIN-. A maximum of 9A load should be
connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I.
IR3899 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc
is required, then R15 can be removed and external Vcc can be applied between Vcc+ and Vcc- pins. Vin pin
and Vcc/LDOout pins should be shorted together for external Vcc operation.
The output can track voltage at the Vp pin. For this purpose, Vref pin is to be connected to ground (use zero
ohm resistor for R21).
The value of R14 and R20 can be selected to provide the desired tracking ratio
between output voltage and the tracking input.
CONNECTIONS and OPERATING INSTRUCTIONS
LAYOUT
The PCB is a 4-layer board (2.23
”x2”) using FR4 material. All layers use 2 Oz. copper. The PCB
thickness is 0.062
”. The IR3899 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 IR3899. 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.
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
P_Good
Power Good Signal
AGnd
Analog ground