1
®
AN1391.0
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Using the ISL6443AEVAL2Z Evaluation Board
Using the Evaluation Board
The ISL6443A is a high performance triple-output controller
offering control and protection features for 2 synchronous
buck PWMs and 1 linear regulator.
The ISL6443A evaluation board highlights the operation of
the IC in an embedded DC/DC converter application. Table 1
shows the available evaluation board.
Recommended Test Equipment
• A 12V, 5A capable power supply
• An electronic load
• Four channel oscilloscope with probes
• Precision digital multimeters
Power and Load Connections
Input Voltage
To connect a +12V power supply to the evaluation board,
connect the positive lead of the power supply to the VIN (P1)
post and the ground lead of the supply to the GND (P2) post.
The input voltage to the linear controller is already taken
from the 1.8V output of V
OUT2.
Output Adjustment
Change the respective output voltage feedback resistors to
modify the output voltage using Equation 1:
Soft-Start and Shutdown
The soft-start capacitors can be adjusted for sequencing of
the output voltages, PWM start-up tracking, and/or to adjust
the start-up 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 posts, P9 and P10
respectively.
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. PGOOD can be monitored at
post P8.
Overcurrent Protection
The overcurrent thresholds can be adjusted on the
ISL6443A evaluation board. The current sense resistors,
I
SENSE
, are set at 1.0k
Ω
. The overcurrent set resistor is
95.3k
Ω
. The overcurrent trip point can be adjusted by
modifying R
OCSET
, R
5
and R
10
:
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 ISL6443A Data Sheet for more
information on how to select the current sense and
overcurrent select resistors.
TABLE 1. EVALUATION BOARDS
BOARD NAME
IC
PACKAGE
ISL6443AEVAL2Z
ISL6443AIRZ
28 Ld QFN
V
OUT1
0.8
1
R
1
R
2
-------
+
⎝
⎠
⎜
⎟
⎛
⎞
⋅
=
V
OUT2
0.8
1
R
3
R
4
-------
+
⎝
⎠
⎜
⎟
⎛
⎞
⋅
=
V
OUT3
0.8
1
R
6
R
11
----------
+
⎝
⎠
⎜
⎟
⎛
⎞
⋅
=
(EQ. 1)
t
SS PWM1
(
)
C
2
0.8V
5
μ
A
------------
⋅
=
t
SS PWM2
(
)
C
3
0.8V
5
μ
A
------------
⋅
=
(EQ. 2)
R
OCSET
7 R
CS
⋅
I
OC
r
DS ON
(
)
⋅
-------------------------------------
=
(EQ. 3)
Application Note
March 10, 2008
