AP1533
PWM CONTROL 1.8A STEP-DOWN CONVERTER
AP1533 Rev. 4 1 of 9 JULY 2009
DS31192 www.diodes.com © Diodes Incorporated
• Input voltage: 4V to 23V
• Output voltage: 0.8V to V
CC
• 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)
• Lead Free Finish/ RoHS Compliant (Note 1)
AP1533 consists of step-down switching regulator with PWM
control. These devices include a reference voltage source,
oscillation circuit, error amplifier, internal PMOS.
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.
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.
• PC Motherboard
• LCD Monitor
• Graphic Card
• DVD-Video Player
• Telecom Equipment
• ADSL Modem
• Printer and other Peripheral Equipment
• Microprocessor core supply
Typical Application Circuit
AP1533
+
-
V
SS
EN
C
C
R
A
R
B
D1*
FB
Vcc
Output
CVcc
V
OUT
=5V/1.8A
V
IN
R
OCSET
OCSET
C
OUT
C
IN
Optional
C
OCSET
C
EN
R
EN
Option
100K
L1
33uH
6.8K
1.3K
3.3K
0.1uF
+
-
C
0.1uF 470uF
470uF
0.1uF
*
Suggested DIODES Power Schottky P/N: B340 series or PDS340.
V
OUT
=
V
FB
x (
1+
R
A
/R
B
)
R
B
= 0.7K~5K ohm
Features
General Description
Applications
