TS3404

Single Synchronous Buck PWM Controller

Oscillator Frequency up to 300KHz

0.8V Internal Reference

Drives N-Channel MOSFETs

General Description

The TS3405 makes simple work out of implementing a complete control and protection scheme for a DC-DC step-down

converter. Designed to drive N-channel MOSFETs in a synchronous buck topology, the TS3405 integrates the control,

output a adjustment, monitoring and protection functions.

The TS3405 provides simple, single feedback loop, voltage mode control with fast transient response. The output voltage

can be precisely regulated to as low as 0.8V, with a maximum tolerance of ±1.5% over temperature and line voltage

variations. A fixed frequency oscillator reduces design complexity, while balancing typical application cost and efficiency.

The error amplifier features a 15MHz gain-bandwidth product and 8V/uS slew rate, which enables high converter

bandwidth for fast transient performance. The resulting PWM duty cycles range from 0% to 100%. The protection from

over current conditions is provided by monitoring the Rds(on) of the lower MOSFET to inhibit PWM operation

appropriately. This approach simplifies the implementation and improves efficiency by eliminating the need for a current

sense resistor.

Applications

Power supplies for microprocessors

Subsystem power supplies

Cable modems, set-top box, DSL modems

DSP and core communications processor supplies

Memory supplies

Personal computer peripherals

Industrial power supplies

Low-voltage distributed power supplies

Features

Buck converter Vin operate from 3.3V ~ 14V

Vcc operate from 3.75V ~ 6V

Buck converter Vin can be greater than Vcc

0.8V to Vin output voltage

±1.5% over line voltage and temperature

Simple single –loop control design

Voltage-mode PWM control

Loss less, programmable over current protection

uses lower MOSFET’s Rds(on)

Internal soft start

Converter can source and sink current

Fixed oscillator frequency 300KHz

Ordering Information

Part No.

Operating Temp.

Package

TS3405CS

-40 ~ +85

SOP-8

Absolute Maximum Rating

Supply Voltage

6

V

Operating Supply Voltage

4.5 ~ 5.5

V

Absolute Boot Voltage

20

V

Upper Driver Supply Voltage

20

V

Input, Output or I/O Voltage

Gnd-0.3V to Vcc+0.3V

V

Operating Junction Temperature Range

-40 ~ +125

Ambient Temperature Range

-40 ~ +85

Storage Temperature Range

-65 ~ +150

Lead Temperature 1.6mm(1/16”) from case for 10Sec.

260

Pin assignment

1. Boot

8. Phase

2. Ugate

7. COMP

3. Gnd

6. FB

4. Lgate

5. Vcc

TS3405

1-10

2003/12 rev. A