Diodes AP3435 User Manual

1.0MHz, 3.5A, Synchronous Step Down DC-DC Converter AP3435

Preliminary Datasheet

General Description

The AP3435 is a high efficiency step-down DC-DC voltage converter. The chip operation is optimized by peak-current mode architecture with built-in synchronous power MOS switchers. The oscillator and timing capacitors are all built-in providing an internal switching frequency of 1MHz that allows the use of small surface mount inductors and capacitors for portable product implementations.

Integrated Soft Start (SS), Under Voltage Lock Out (UVLO), Thermal Shutdown Detection (TSD) and Short Circuit Protection are designed to provide reliable product applications.

The device is available in adjustable output voltage versions ranging from 0.8V to 0.9×V (2.7V≤VIN≤5.5V), and is able to deliver up to 3.5A.

The AP3435 is available in PSOP-8 package.

Features

• High Efficiency Buck Power Converter

• Output Current: 3.5A

• Low R

• Adjustable Output Voltage from 0.8V to 0.9×V

• Wide Operating Voltage Range: 2.7V to 5.5V

•

Built-in Power Switches for Synchronous

Rectification with High Efficiency

• Feedback Voltage: 800mV

• 1.0MHz Constant Frequency Operation

• Thermal Shutdown Protection

• Low Drop-out Operation at 100% Duty Cycle

• No Schottky Diode Required

• Input Over Voltage Protection

Applications

IN

• LCD TV

• Set Top Box

• Post DC-DC Voltage Regulation

• PDA and Notebook Computer

Internal Switches:100mΩ (VIN=5V)

DS(ON)

Figure 1. Package Type of AP3435

PSOP-8

IN

Dec. 2012 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

1.0MHz, 3.5A, Synchronous Step Down DC-DC Converter AP3435

Pin Configuration

MP Package

(PSOP-8)

Pin Description

Pin Number Pin Name Function

1 VCC Supply input for the analog circuit

2 NC No connection

1

2

3

4

Figure 2. Pin Configuration of AP3435 (Top View)

8

7

6

5

3 GND Ground pin

4 FB

5 EN

6 PGND Power switch ground pin

7 SW Switch output pin

8 VIN Power supply input for the MOSFET switch

Feedback pin. Receive the feedback voltage from a resistive divider connected across the output

Chip enable pin. Active high, internal pull-high with 200kΩ resistor

Dec. 2012 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

1.0MHz, 3.5A, Synchronous Step Down DC-DC Converter AP3435

Functional Block Diagram

FB

EN

5

Saw-Tooth

Generator

Bias

Generator

Soft

Start

4

Bandgap

Reference

_

+

Error

Amplifier

_

+

Oscillator

+

+ _

Modulator

Over Voltage

Comparator

Over-Current

Comparator

Control

Logic

VCC

1

Current

Sensing

Buffer &

Dead Time

Control

Logic

_

+

Reverse Inductor

Current Comparator

3

VIN

8

6

7

SW

GND

Figure 3. Functional Block Diagram of AP3435

PGND

Ordering Information

AP3435 -

Circuit Type

Package MP: PSOP-8

Package

Temperature

Range

Part Number Marking ID Packing Type

PSOP-8 -40 to 80°C AP3435MPTR-G1 3435MP-G1 Tape & Reel

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

G1: Green

TR: Tape & Reel

Dec. 2012 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

1.0MHz, 3.5A, Synchronous Step Down DC-DC Converter AP3435

Absolute Maximum Ratings (Note 1)

Parameter Symbol Value Unit

Supply Input for the Analog Circuit VCC

Power Supply Input for the MOSFET Switch VIN

SW Pin Switch Voltage VSW

Enable Input Voltage VEN

SW Pin Switch Current ISW

Power Dissipation (on PCB, TA=25°C)

Thermal Resistance (Junction to Ambient, Simulation)

Operating Junction Temperature TJ

Operating Temperature TOP

Storage Temperature T

ESD (Human Body Model) V

ESD (Machine Model) VMM

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.

PD 2.47 W

θJA 40.43 °C/W

STG

HBM

0 to 6.0

-0.3 to VIN+0.3

-0.3 to V

-40 to 85

-55 to 150

4.5

160

2000

200

IN

+0.3

V

A

°C

V

Recommended Operating Conditions

Parameter Symbol Min Max Unit

Supply Input Voltage VIN 2.7 5.5 V

Junction Temperature Range TJ -40 125 °C

Ambient Temperature Range TA -40 80 °C

Dec. 2012 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

1.0MHz, 3.5A, Synchronous Step Down DC-DC Converter AP3435

Electrical Characteristics

VIN=VCC=VEN=5V, V

specified.

Parameter Symbol Conditions Min Typ Max Unit

Input Voltage Range

Shutdown Current I

Active Current ION V

Regulated Feedback Voltage Regulated Output Voltage Accuracy Peak Inductor Current Oscillator Frequency

PMOSFET RON R

NMOSFET RON R

EN High-level Input Voltage EN Low-level Input Voltage

EN Input Current

Soft Start Time

Maximum Duty Cycle

Under Voltage Lock Out Threshold

Thermal Shutdown TSD Hysteresis=30°C

Input Over Voltage Protection (IOVP)

=1.2V, VFB=0.8V, L=2.2μH, CIN=10μF, C

OUT

ΔV

OUT/VOUT

V

D

V

IN

V

OFF

V

FB

4.5 A

I

PK

V

f

OSC

VIN=5V

ON(P)

VIN=5V

ON(N)

EN_H

EN_L

I

EN

t

SS

MAX

=0

EN

=0.95V

FB

For Adjustable Output Voltage

=2.7V to 5.5V,

V

IN

=0 to 3.5A

I

OUT

=2.7V to 5.5V

IN

1.5 V

0.4 V

1 μA

400 μs

100 %

2.7 5.5 V

Rising

V

UVLO

Falling

Hysteresis

Rising

V

IOVP

Hysteresis

=22μF, TA=25°C, unless otherwise

OUT

1 μA

310 μA

0.784 0.8 0.816 V

-3 3 %

1.0 MHz

100 mΩ

2.4

2.3

0.1

150 °C

5.8 5.9 6.0 V

0.3 0.4 0.5 V

V

Dec. 2012 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

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Preliminary Datasheet

1.0MHz, 3.5A, Synchronous Step Down DC-DC Converter AP3435

Typical Performance Characteristics

100

90 80 70 60 50 40

Efficiency (%)

30 20 10

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Output Current (A)

VIN=5V, V

OUT

=1.2V

100

90 80 70 60 50 40

Efficiency (%)

30 20 10

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Output Current (A)

VIN=5V, V

OUT

=3.3V

Figure 4. Efficiency vs. Output Current

Figure 5. Efficiency vs. Output Current

1.24

1.23

1.22

1.21

1.20

1.19

Output Voltage (V)

1.18

1.17

1.16

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Output Current (A)

VIN=5V, V

OUT

=1.2V

3.40

3.38

3.36

3.34

3.32

3.30

3.28

Output Voltage (V)

3.26

3.24

3.22

3.20

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Output Current (A)

VIN=5V, V

OUT

=3.3V

Figure 6. Load Regulation Figure 7. Load Regulation

Dec. 2012 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

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