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© 2013 Exar Corporation
5/18
Rev. 1.0.0
USING THE EVALUATION BOARD
I
NPUT
V
OLTAGE
C
ONFIGURATION
The XRP7740EVB-HIC demo board has several
different input voltage options. The power
components have been optimized for a 12V
input rail. When running the board at an input
voltage other than 12V, use PowerArchitect
TM
4.xx to evaluate the system performance.
Single Wide Range, Input Voltage Rail
The XRP7740EVB-HIC Board ships from the
factory configured for a single wide range
input. The normal input voltage range is from
7.0V to 20V. With the on board charge pump
enabled the input voltage range for the board
is 4.5V to 20V.
I
2
C
I
NTERFACE
The XRP77XX family of controllers employs a
standard I2C interface. Pull-ups for the I2C
signals are included on the demo board and
may be selected by means of a configuration
jumper. If using the demo board with
something other than the XRP77xxEVB-XCM,
verify that the SDA and SCL lines are pulled
up, either by the external controller or with
the on board pull ups.
Channel Design and Limitations
Channel 1 is designed to provide an output
voltage from 0.9V to 5.0V. The default voltage
is 1.5V at 8A.
Channel 2 is designed to provide an output
voltage from 0.9V to 2.0V. The default voltage
is 1.0V at 30A. The limiting factors are the
output capacitors which has a 2.5V rating.
Channel 3 is designed to provide an output
voltage from 0.9V to 5.0V. The default
voltage is 1.8V at 5A.
Channel 4 is designed to provide an output
voltage from .9 to 5.0V. The default voltage is
1.0V at 12A.
E
NABLE
P
IN
The ENABLE pin connects to an RC network
which delays turn on of the device. It is
connected to J3 pin 9 of the XCM connector
and J1 pin 15 with a 10K resistor and to
ground through a .1uF capacitor. These pins
can be used to turn on or turn off the device.
S
PECIAL
B
OARD
F
EATURES
The board is comes from the factory wired for
7V to 20V operation. Input power can be
applied either through the Power Jack, J12, or
through the terminal block J13. The center
lead of the J12 connector is positive.
In addition to the four XRP7740 switching
power supplies. There are two other power
supplies on the board. One is an external 5V
LDO and the other is a charge pump tripler.
The external 5V LDO can be used to power the
gate drives for the switching FETs to decrease
the power dissipated by the internal chip 5V
LDO.
The charge pump runs off of the on board 5V
LDO and supplies a boosted voltage to the
XRP7740 Vin pin to allow for operation with
board input voltages down to 4.0V.
Configuring the Evaluation Board
The connections and test points on the board
are shown in Figure 5. Please observe the
correct voltage polarities for the inputs and
outputs.
As you go clockwise around the edge of the
board, the polarities are on the connectors are
negative first and then positive for all the
terminals. Also note that, again going
clockwise around the board, the channels are
Ch1, Ch2, Ch4, and then Ch3
. This was done
to match the XRP7740 pin out sequence to
optimize layout of the board.
