RICHTEK RT9202CS Datasheet

Preliminary

RT9202

Single Synchronous Buck PWM DC-DC Controller

General Description

The RT9202 is a single power supply PWM DC-DC

converter controller designed to drive N-channel

MOSFET in a synchronous buck topology. The IC

integrates the control, output adjustment, monitoring

and protection functions in a small 8-pin package.

The RT9202 uses a low gain voltage mode PWM

control for simple application design. An internal 0.8V

reference allows the output voltage to be precisely

regulated to low voltage requirement. A fixed 300kHz

oscillator reduces the component size for saving

board space.

The RT9202 features over current protection, over

voltage protection, and under voltage lock-out. The

output current is monitored by sensing the voltage

drop across the MOSFET’s R

, which eliminates

DS(ON)

the need for a current sensing resistor.

Applications

Motherboard Power Regulation for Computers

z

Subsystems Power Supplies

z

Cable Modems, Set Top Box, and DSL Modems

z

DSP and Core Communications processor Supplies

z

Memory Power Supplies

z

Personal Computer Peripherals

z

Industrial Power Supplies

z

5V-Input DC-DC Regulators

z

Low Voltage Distributed Power Supplies

z

Features

z

Operate from 5V

z

0.8V Internal Reference

z

Drive Two N-channel MOSFET

z

Voltage Mode PWM Control

z

Fast Transient Response

z

Fixed 300kHz Oscillator Frequency

z

Full 0~100% Duty Cycle

z

Internal Soft Start

z

Adaptive Non-overlapping Gate Driver

z

Over-current Monitor Uses MOSFET R

z

Over-voltage Protection Uses Low-side

DS(ON)

MOSFET

Pin Configurations

Part Number Pin Configurations

GND

TOP VIEW

1

2

3

4

8

7

6

5

PHASE

OCSET

FB

VCC

RT9202CS

(Plastic SOP-8)

BOO T

UGATE

LGATE

Ordering Information

RT9202 

Package type

S : SOP-8

Operating temperature range

C: Commercial standard

DS9202-01 March 2002 www.richtek-ic.com.tw

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RT9202

Typical Application Circuit

Preliminary

SHDN

H: shutdown

Q2 2N7002

R1

R4

10

V

2.5V

R2

255

C6

10nF

C2

0.1µF

OU T

1

2

3

4

C4 1µF

8

7

6

5

PHASE

OCSET

RT9202

FB

VCC

20K

BOOT

UGATE

GND

LGATE

R3

120

Fig.1 RT9202 powered from 5V only

D1

MA732

+

C3 1000µF

L2

5µH

MU

ML

5V

C5 1µF

+

C1 470µF

H: shutdown

SHDN

Q1 2N7002

C4 1µF

R1

20K

8

7

6

5

PHASE

OCSET

RT9202

FB

VCC

UGATE

LG ATE

R3

120

BOOT

GND

1

2

V

OU T

2. 5V

3

4

R2

250

C6

10nF

Fig.2 RT9202 powered from 12V

C2 1µF

R4

10

+

C3 1000µF

L1

5µH

MU

ML

12V

5V

C5 1µF

+

C1 470µF

www.richtek-ic.com.tw DS9202-01 March 2002

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Preliminary

MU

+

COUT

CVCC 1µF

GND

VCC

RT9202

1000µF

CBOOT

BOOT

0.1µF

L 5µH

Layout Placement

Layout Notes

1. Put CIN1 & CIN2 to be near the MU drain and ML source nodes.

2. Put RT9202 to be near the COUT

3. Put CBOOT as close as to BOOT pin

4. Put CVCC as close as to VCC pin

D

GS

ML

D

GS

GND Re tur n

CIN1 1µF

+

RT9202

CIN2 470µF

DS9202-01 March 2002 www.richtek-ic.com.tw

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RT9202

Function Block Diagram

Preliminary

VCC

FB

GND

Bias

0.8V

Reference

0.8V

Error

6.0V

Regulator

Power on

Reset

40µA

Soft Start

+

OC

_

1V

0.5V

+

35dB

_

Erro r Amp

_

OVP

+

_

UVP

+

300kH z

Oscillator

+

PWM

_

Control

Logic

VCC

BOOT

OCSET

UGATE

PHASE

LGATE

www.richtek-ic.com.tw DS9202-01 March 2002

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Preliminary

RT9202

Absolute Maximum Ratings

z

Supply Voltage VCC 7V

z

BOOT & UGATE to GND 15V

z

Input, Output or I/O Voltage GND−0.3V ~ 7V

z

Power Dissipation, PD @ TA = 25°C

SOP-8 0.625W

z

Package Thermal Resistance

SOP-8, θ

z

Ambient Temperature Range 0°C ~ +70°C

z

Junction Temperature Range -40°C ~ +125°C

z

Storage Temperature Range -65°C ~ +150°C

z

Lead Temperature (Soldering, 10 sec.) 260°C

JA

160°C/W

CAUTION:

Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the

device. This is a stress only rating and operation of the device at these or any other conditions above those

indicated in the operational sections of this specification is not implied.

Electrical Characteristics

(V

= 5V, TA = 25°C, Unless otherwise specified.)

CC

Parameter Symbol Test Conditions Min Typ Max Units

VCC Supply Current / Regulated Voltage

Nominal Supply Current

Regulated Voltage from BOOT

I

V

CC

UGATE, LGATE open -- 3 -- mA

V

BOOT

= 12V

-- 6.0 -- V

Power-On Reset

Rising VCC Threshold

VCC Threshold Hysteresis

Rising V

OCSET

Threshold

V

OCSET

V

OCSET1

= 4.5V

3.85 4.1 4.35 V

0.3 0.5 0.7 V

0.8 1.25 2.0 V

Reference

Reference Voltage 0.784 0.8 0.816 V

Oscillator

Free Running Frequency 250 300 350 KHz

Ramp Amplitude

∆ V

OSC

-- 1.9 --

Error Amplifier

DC gain -- 35 -- dB

PWM Controller Gate Driver

V

P-P

Upper Drive Source

Upper Drive Sink

Lower Drive Source

Lower Drive Sink

R

UGATE

R

UGATE

R

LGATE

R

LGATE

BOOT= 12V BOOT-V

V

UGATE

VCC - V

V

LGATE

UGATE

= 1V

LGATE

= 1V

= 1V,

-- 7 --

-- 5 --

-- 4 --

-- 2 --

Ω

To be continued

DS9202-01 March 2002 www.richtek-ic.com.tw

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