AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
General Description
Features
AP1533 consists of step-down switching regulator with PWM
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Input voltage: 4V to 23V
Output voltage: 0.8V to VCC
control. These devices include
a reference voltage source,
oscillation circuit, error amplifier, internal PMOS.
Output current: 1.8A up to peak 2A
Duty ratio: 0% to 99% PWM control
Oscillation frequency: 300KHz typ.
Soft-start like, Current limit and Enable function
Thermal Shutdown function
Built-in internal SW P-channel MOS
SOP-8L: Available in “Green” Molding Compound
(No Br, Sb)
AP1533 provides low-ripple power, high efficiency, and excellent
transient characteristics. The PWM control circuit is able to vary
the duty ratio linearly from 0 up to 99%. This converter also
contains an error amplifier circuit as well as a soft-start circuit that
prevents overshoot at startup. An enable function, an over current
protect function and a short circuit protect function are built inside,
and when OCP or SCP happens, the operation frequency will be
reduced from 300KHz to 50KHz. Also, an internal compensation
block is built in to minimum external component count.
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Lead Free Finish/ RoHS Compliant (Note 1)
With the addition of an internal P-channel Power MOS, a coil,
capacitors, and a diode connected externally, these ICs can
function as step-down switching regulators. They serve as ideal
power supply units for portable devices when coupled with the
SOP-8L mini-package, providing such outstanding features as low
current consumption. Since this converter can accommodate an
input voltage up to 23V, it is also suitable for the operation via an
AC adapter.
Applications
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PC Motherboard
LCD Monitor
Graphic Card
DVD-Video Player
Telecom Equipment
ADSL Modem
Printer and other Peripheral Equipment
Microprocessor core supply
Typical Application Circuit
VOUT=5V/1.8A
L1
Vcc
V
Output
IN
33uH
CC
RA
6.8K
ROCSET COCSET
3.3K
AP1533
Option
Optional
+
-
+
FB
C IN
OCSET
EN
C
COUT
0.1uF
470uF
470uF
VSS
-
REN
100K
RB
1.3K
CVcc
0.1uF
D1*
CEN
0.1uF
VOUT
RB
x (
VFB
R /RB)
A
1+
=
= 0.7K~5K ohm
*
Suggested DIODES Power Schottky P/N: B340 series or PDS340.
AP1533 Rev. 4
DS31192
1 of 9
www.diodes.com
JULY 2009
© Diodes Incorporated