Diodes AP3503E User Manual

340kHz, 3A Synchronous DC-DC Buck Converter AP3503E

Preliminary Datasheet

General Description

The AP3503E is a 340kHz fixed frequency, current
mode, PWM synchronous buck (step-down) DC-DC
converter, capable of driving a 3A load with high
efficiency, excellent line and load regulation. The
AP3503E exhibits high efficiency at light load. The
device integrates N-channel power MOSFET
switches with low on-resistance. Current mode
control provides fast transient response and
cycle-by-cycle current limit.

The AP3503E employs complete protection to en sure
system security. Including output Over Voltage
Protection, input Under Voltage Lock Out,
programmable Soft Start, Over Temperature
Protection and hiccup mode Short Circuit Protection.

This IC is available in PSOP-8 package.

Features

• Input Voltage Range: 4.5V to 18V

• Fixed 340kHz Frequency

• High Efficiency at Light Load

• High Efficiency: up to 95%

• Output Current: 3A

• Current Mode Control

• Built-in Over Current Protection

• Built-in Thermal Shutdown Function

• Built-in UVLO Function

• Built-in Over Voltage Protection

• Programmable Soft-start

• Hiccup Mode SCP

Applications

• LCD TV

• Set Top Box

• Portable DVD

• Digital Photo Frame

PSOP-8

Figure 1. Package Type of AP3503E

May. 2012 Rev. 1. 6 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

340kHz, 3A Synchronous DC-DC Buck Converter AP3503E

Pin Configuration

MP Package
(PSOP-8)

1

2

3

4

8

7

6

5

Figure 2. Pin Configuration of AP3503E (Top View)

Pin Description

Pin Number Pin Name Function

Bootstrap pin. A bootstrap capacitor is connected between the BS pin

1

2

3
4

5

6

7

8

BS

and SW pin. The voltage across the bootstrap capacitor drives the
internal high-side power MOSFET

IN

SW

Supply power input pin. A capacitor should be connected between the
IN pin and GND pin to keep the input voltage constant
Power switch output pin. This pin is connected to the inductor and
bootstrap capacitor

GND Ground pin

Feedback pin. This pin is connected to an exte rnal resistor divider to
program the system output voltage. When the FB pin voltage exceeds

FB

1.1V, the over voltage protection is triggered. When the FB pin
voltage is below 0.3V, the oscillator frequency is lowered to realize
short circuit protection
Compensation pin. This pin is the output of the transconductance
error amplifier and the input to the current comparator. It is used to

COMP

compensate the control loop. Connect a series RC network from this
pin to GND. In some cases, an additional capacitor from this pin to
GND pin is required
Control input pin. EN is a digital in put that turns the regulator on or

EN

off. Drive EN high/low to turn on/off the regulator. Pull up with
100kΩ resistor for automatic startup
Soft-start control input pin. SS controls the soft-start period. Connect

SS

a capacitor from SS to GND to set the soft-start period. A 0.1µF
capacitor sets the soft-start period to 15ms. To disable the soft-start
feature, leave SS unconnected

EP Exposed pad. It should be connected to GND in PCB layout

May. 2012 Rev. 1. 6 BCD Semiconductor Manufacturing Limited

2

Preliminary Datasheet

340kHz, 3A Synchronous DC-DC Buck Converter AP3503E

Functional Block Diagram

2

IN

EN

7

1.5V

SHUTDOWN
COMPARATOR

0.3V

LOCK

COMPARATOR

SCP

INTERNAL

REGULATOR

OSCILLATOR

90K/340K

CLK

VA
VB

SLOP

COMP

CURRENT

SENSE

AMPLIFIER

S
R

PWM

COMPARATOR

VA

+

1

M1

Q
Q

M2

BS

3

SW

2.5V

SS

VB

1.1V

A

8

5

EA

5

0.

925V

6

COMPFB

4

GND

Figure 3. Functional Block Diagram of AP3503E

Ordering Information

AP3503E -

Circuit Type

Package
MP: PSOP-8

Package

PSOP-8

Temperature

Range

-40 to 85°C

Part Number Marking ID Packing Type

AP3503EMP-G1 3503EMP-G1 Tube
AP3503EMPTR-G1 3503EMP-G1 Tape & Reel

BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS
compliant and green.

G1: Green

TR: Tape & Reel
Blank: Tube

May. 2012 Rev. 1. 6 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

340kHz, 3A Synchronous DC-DC Buck Converter AP3503E

Absolute Maximum Ratings (Note 1)

Parameter Symbol Value Unit

IN Pin Voltage VIN -0.3 to 20 V
EN Pin Voltage VEN -0.3 to VIN V
SW Pin Voltage VSW 21 V
BS Pin Voltage VBS -0.3 to VSW+6 V
FB Pin Voltage VFB -0.3 to 6 V
COMP Pin Voltage V
SS Pin Voltage VSS -0.3 to 6 V
Thermal Resistance
Operating Junction Temperature TJ 150 ºC
Storage Temperature T
Lead Temperature (Soldering, 10sec) T
ESD (Human Body Model) V
ESD (Machine Model) VMM

-0.3 to 6 V

COMP

θ

JA

-65 to 150 ºC

STG

260 ºC

LEAD

HBM

60 ºC/W

2000

200

V
V

Note 1: Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to
the device. These are stress ratings only, and functional operation of the device at these or any other conditions
beyond those indicated under “Recommended Operating Conditions” is not implied. Exposure to “Absolute
Maximum Ratings” for extended periods may affect device reliability.

Recommended Operating Conditions

Parameter Symbol Min Max Unit

Input Voltage VIN 4.5 18 V
Operating Ambient Temperature TA -40 85 ºC

May. 2012 Rev. 1. 6 BCD Semiconductor Manufacturing Limited

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