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Application Note 1031
Oct. 2009 Rev. 1. 1 BCD Semiconductor Manufacturing Limited
1
SW
GND
FB
V
IN
OV
CTRL
1
2
34
5
Pin 1 Dot by Marking
6
1
2
3
4
8
7
6
5
SW
GND
FB
GND
OV
CTRL
V
IN
GND
Q1
Σ
A2
A1
1MHz
OSCILLATOR
RAMP
GENERATOR
V
REF
DRIVER
1.25 V
COMPARATOR
200 mV
SOFT
START
V
IN
CTRL
FB
GND
SW
STANDBY
OV
To Control
Logic
CONTROL
LOGIC
OVER
TEMPERATURE
DETECTOR
OV
3 (1) 1 (4)
5 (7)
2
(2, 3, 6)
4 (8)
6 (5)
Design Consideration with AP3031
Prepared by Han Lu
System Engineering Dept.
1. Introduction
The AP3031 is an inductor-based DC/DC boost
converter designed to drive LED arrays. 1.4A
switching current allows AP3031 to be used in
different 7' to 10' LCD panel backlights (3*13 LED
arrays typically). The output current accuracy is
determined by the feedback voltage and resistor
R
ISET
.
To save space and reduce cost, this AP3031 operates
at 1MHz normally, which means that the tiny
periphery components are acceptable. In fact, 1mm
tall 4.7µH inductor and 0.47µF output capacitors for
typical applications are very appropriate.
An OVP circuit is integrated in this chip, which
protects the IC under open load condition. The
AP3031 includes UVLO, soft-start, current limit and
OTSD to protect the circuit.
To achieve flexible maneuverability, a control
terminal is designed to turn on or turn off this device.
In practice, adding a PWM signal on this terminal to
control the luminous intensity is a good idea. The
main application field of the AP3031 consists of 7’ to
10’ LCD panels, including digital photo frame, GPS
receiver, EPC, PDVD, etc. As is well known, the
main feature of these handheld devices is
compactness. To satisfy the requirements for small
mounting space constraints, this IC is available in
small SOT-23-6, TSOT-23-6 and SOIC-8 packages
to save space.
2. Functional Block Description
The pin configuration and the representative block
diagram of the AP3031 are respectively shown in
Figure 1 and Figure 2.
SOT-23-6/TSOT-23-6 SOIC-8
Figure 1. Pin Configuration of AP3031 (Top View)
A (B)
A SOT-23-6/TSOT-23-6
B SOIC-8
Figure 2. Functional Block Diagram of AP3031
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