IRDC3892
SupIRBuck
DESCRIPTION
TM
USER GUIDE FOR IRDC3892 EVALUATION BOARD
The IR3892 is a dual synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mm X 6mm Power QFN package.
Key features offered by the IR3892 include
internal Digital Soft Start, precision 0.5V
reference voltage, Power Good, thermal
protection,
programmable
switching
frequency, Enable input, input under-voltage
lockout for proper start-up, enhanced line/
load regulation with feed forward, external
frequency synchronization with smooth
clocking, internal LDO, pre-bias start-up,
output over voltage protection as well as open
feedback line protection.
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 and the current limit is thermally
compensated.
This user guide contains the schematic and bill
of materials for the IRDC3892 evaluation board.
The guide describes operation and use of the
evaluation board itself. Detailed application
information for IR3892 is available in the
IR3892 data sheet.
BOARD FEATURES
•
V
in
= +12.0V
•
Fs = 600kHz
•
V
out1
= +1.8V @ 6A
•
L
1
= 1.0uH
•
C
out1
=4x22uF (ceramic 0805)
•
C
in
= 4x10uF (ceramic 1206) + 1x330uF (electrolytic)
V
out2
= +1.2V @ 6A
L
2
= 1.0uH
C
out2
=4x22uF (ceramic 0805)
7/17/2013
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IRDC3892
CONNECTIONS and OPERATING INSTRUCTIONS
A well regulated +12.0V input supply should be connected to VIN+ and VIN-. A maximum 6A 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.
IR3892 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc
is required, then R3 should be removed and external Vcc should be applied between Vcc+ and Vcc- pins.
Vin pin (input of the LDO) and Vcc/LDO pins should be shorted together (populate R4) for external Vcc
operation.
The output of channel2 (Vout
2
) can follow the voltage at the Seq pin. For this purpose, The value of R5 and
R6 can be selected to provide the desired sequencing ratio between Seq input and Vout
2
. For normal
operation (non-sequencing) Seq pin should be left floating. Seq pin is internally pulled up to 3.3V.
Table I. Connections
Connection
VIN+
VIN-
VOUT1+
VOUT1-
VOUT2+
VOUT2-
VCC+
VCC-
VSEQ
EN1, EN2
Sync
Signal Name
PV
in
(+12V)
Ground of PV
in
V
out1
(+1.8V)
Ground of Vout
1
V
out2
(+1.2V)
Ground of Vout
2
VCC/LDO pin
Connected to PGND
Sequence input
Enable input of each channel
Synchronous input
LAYOUT
The PCB is a 4-layer board. All of layers are 2 Oz. copper. The IR3892 and other components are
mounted on the top and bottom side of the board.
Power supply decoupling capacitors, the Bootstrap capacitor and feedback components are located
close to IR3892. The feedback resistors are connected to the output voltage at the point of regulation
and are located close to IR3892. To improve efficiency, the circuit board is designed to minimize the
length of the on-board power ground current path.
7/17/2013
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