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AN1130
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Using the ISL6402, ISL6402A Evaluation Board
Using the Evaluation Board
The ISL6402 and ISL6402A are high performance triple-
output controllers offering control and protection features for
2 synchronous buck PWMs and 1 linear regulator.
The ISL6402, ISL6402A evaluation boards highlight the
operation of the IC in embedded DC-DC converter
applications. Table 1 shows the available evaluation boards.
Recommended Test Equipment
• A 4.5V-24V, 5A capable power supply
• An electronic load
• Four channel oscilloscope with probes
• Precision digital multimeters
Power and Load Connections
Input Voltage - The input power supply can be connected in two
different ways depending on the input voltage supplied to the
PWM power stage. When connecting to a 5.6V-20V power
supply, connect the positive lead of the power supply to VIN (P1)
post and the ground lead of the supply to the GND (P2) post.
When connecting to a 4.5V-5.5V input, the Vin (P1) and
VCC_5V (P10) posts must be shorted using the jumper (JP1)
before connecting the positive lead of the supply to the
Vin (P1) post and the ground lead to the GND (P2) post.
The input voltage to the linear regulator can be supplied from
a 3.3V/5V power supply by connecting the positive lead of
the power supply to the VIN3 (P13) post and the ground
terminal to the GND (P14) post.
Output Adjustment
Change the respective output voltage feedback resistors to
modify the output voltage:
Soft Start and Shutdown
The soft start capacitors can be adjusted for sequencing of
the output voltages, PWM startup tracking, and/or to adjust
the startup current required to charge the output capacitors.
To independently shutdown the PWMs, the SD1 or SD2 pin
can be pulled to GND using the on board jumpers, JP2 and
JP3 respectively.
SYNC Function
The ISL6402, ISL6402A can synchronize to another
ISL6402, ISL6402A. The SYNC pin sends out pulses at 4
times the switching frequency for the ISL6402A and 16 times
the switching frequency of the ISL6402. The SYNC function
is bidirectional so if two or more ICs are SYNC, only 1 will be
the master. All other ICs will SYNC to the master. The SYNC
feature can be evaluated on the eval board. The SYNC pin
us pulled to VCC_5V through R17. This resistor should be
removed an a 1K resistor should be placed at R19. With the
1K resistor from SYNC to ground, the SYNC pulses can be
observed on a scope.
Power Good
When both PWMs are within ±10% of their set value and the
linear regulator output is within 75% of its set value, the
PGOOD signal will go high. The open drain PGOOD pin is
pulled HIGH to VCC_5V on the board. The PGOOD circuitry
monitors the FBx pin of each regulated output to determine if
the outputs are in regulation. If the linear controller is not
used, the VOUT3 post P15 can be tied to VCC_5V so that
the PGOOD function can be evaluated without the linear
output. PGOOD can be monitored at post P8.
Overcurrent Protection
The overcurrent thresholds can be adjusted on the ISL6402,
ISL6402A evaluation board. The current sense resistors,
I
SENSE
, are set at 1.4K. The overcurrent set resistor is
120K. The overcurrent trip point can be adjusted by
modifying R
OCSET
, R11 and R12:
R
OCSET
is the overcurrent set resistor, R
CS
is the current
sense resistor, I
OC
is the desired overcurrent trip point, and
r
DS(ON)
is the on resistance of the respective PWM’s lower
MOSFET. Refer to the ISL6402, ISL6402A datasheets for
more information on how to select the current sense and
overcurrent select resistors.
TABLE 1. EVALUATION BOARDS
BOARD NAME IC PACKAGE
ISL6402EVAL4 ISL6402IR 28 Ld QFN
ISL6402AEVAL4 ISL6402AIR 28 Ld QFN
V
OUT1
0.8 1
R
7
R
8
-------+
⋅=
V
OUT2
0.8 1
R
9
R
10
----------+
⋅=
V
OUT3
0.8 1
R
15
R
16
----------+
⋅=
t
SS PWM1()
C
6
0.8V
5µA
------------
⋅= t
SS PWM2()
C
5
0.8V
5µA
------------
⋅=
R
OCSET
7R
CS
⋅
I
OC
R
DS on()
⋅
-------------------------------------=
Application Note May 2004
