TSC TS3404 Technical data

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TS3404

Single Synchronous Buck PWM Controller

Pin assignment

1. Boot 8. Phase

2. Ugate 7. COMP

3. Gnd 6. FB

4. Lgate 5. Vcc

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.

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

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

Ordering Information

Part No. Operating Temp. Package

TS3405CS -40 ~ +85 oC SOP-8

Absolute Maximum Rating

Supply Voltage VCC 6 V

Operating Supply Voltage VCC 4.5 ~ 5.5 V

Absolute Boot Voltage V

Upper Driver Supply Voltage V

Input, Output or I/O Voltage Gnd-0.3V to Vcc+0.3V V

Operating Junction Temperature Range TJ -40 ~ +125

Ambient Temperature Range TJ -40 ~ +85

Storage Temperature Range T

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

BOOT VPHASE

20 V

BOOT

20 V

-65 ~ +150

STG

260

LEAD

TS3405 1-10 2003/12 rev. A

Pin Descriptions

No. Pin. Descriptions

1 Boot

2 Ugate

3 Gnd

4 Lgate

5 Vcc

6 FB

7 COMP

8 Phase

This pin provides ground referenced bias voltage to the upper MOSFET driver. A bootstrap circuit is used to create a voltage suitable to drive a logic-lever N-channel MOSFET. It can take 20V as the maximum voltage. It can be powered by a DC power supply or powered by a boost strap circuit.

This pin provides the PWM controlled gate driver for the upper MOSFET. It is also monitored by the adaptive shoot-through protection circuitry to determine when the upper MOSFET can be turned on. The sourcing Rds(on) is 15Ω and the sink Rds(on) is 7Ω. Ugate can handle high voltage up to maximum 20V.

This pin represents the signal and power ground for the IC. Tie this pin to the ground island/plane through the lowest impedance connection available.

This pin provides the PWM controlled gate drive for the lower MOSFET. This pin is also monitored by the adaptive shoot-through protection circuitry to determine when the lower MOSFET can be turned on.

This pin provides the bias supply for the TS3405, as well as the lower MOSFET’s gate. Connect a well-decoupled 5V supply to this pin.

This pin is the inverting input of the internal error amplifier. Use this pin in combination with the COMP Pin to compensate the voltage-control feedback loop of the converter.

During soft start and all the time during normal converter operation, this pin represents the output of the error amplifier. Use this pin in combination with the FB pin to compensate the voltage control feedback loop of the converter. Pulling COMP to a level below 0.3V enables soft start process. The whole soft start process takes about 5mS.

This pin is used to monitor the voltage drop across the lower MOSFET for over current protection. The OCP threshold is –30mV. If Phases is less thean –300mV, the upper MOSFET cannot be turned-on in the next cycle.

Block Diagram

TS3405 2-10 2003/12 rev. A

Electrical Characteristics (Iout= 0mA, and Tj = +25

C; unless otherwise specified.)

Parameter Symbol Test Conditions Min Typ Max Unit

Vcc supply current

Nominal supply IVcc

2.6 -- 3.8

Power-on reset

Rising Vcc power-on reset

threshold

Vcc power-on reset threshold

POR

3.8 4.0 4.2

0.24 0.25 0.30

Hysteresis

Oscillator

Frequency F

Ramp amplitude ∆V

Vcc= 5V 250 300 340 KHz

OSC

-- 1.5 -- V

OSC

Reference

Reference voltage Tolerance

Nominal reference voltage

REF

-- -- 1.5

-- 0.8 -- V

Error Amplifier

DC Gain -- 82 -- dB

Gain-bandwidth product GBWP 14 -- -- MHz

Slew rate SR COMP= 10pF 4.65 8.0 9.2 V/uS

Gate Drivers

Upper gate source driver I

Upper gate sink driver I

Lower gate source driver I

Lower gate sink driver I

UGATE-SRC

UGATE-SNK

LGATE-SRC

LGATE-SNK

BOOT

VCC

= 10V, I

= 5V, I

UGATE

LGATE

= 100mA

-- 15 --

-- 7 --

-- 9.5 --

-- 3.5 --

Protection / Disable

OCP threshold V

Disable threshold V

OCP

Sweep COMP -- 0.3 -- V

DISABLE

= 5V, sweep Phase -- -300 -- mV

VCC

Typical Application

Ω

Vcc_5V

Roffset

CDCPL

COMP

TS3405

Rfilter

Gnd Vcc

Boot

Vgate

Phase

Lgate

Cbulk

Dboot

Cboot

CHF

Lout

Single Power 5V Application

TS3405 3-10 2003/12 rev. A

Vout

Cout

Typical Application (continued)

Vcc_12VVcc_5V

Rfilter

Roffset

Dboot

CDCPL

COMP

Vcc

TS3405

Gnd

Boot

Vgate

Phase

Lgate

Cboot

Single Power 5V and 12V Application

Vin

CHFCbulk

Vout

Lout

Cout

Roffset

CDCPL

COMP

TS3405

Rfilter

Gnd Vcc

Boot

Vgate

Phase

Lgate

RC1

Dboot

Cboot

RC2

CHFCbulk

Vout

Lout

Cout

Adjustable OCP Point Application

TS3405 4-10 2003/12 rev. A

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