RICHTEK RT9226ACS Datasheet

RT9226A

Synchronous PWM Step-down DC/DC Converter Controller

General Description

The RT9226A is a low cost, high-efficiency voltage-

mode PWM controller for motherboard power supply

application. Synchronous N-channel MOSFET driver,

short-circuit protection, and soft start function are

integrated in a single chip. A simple high power buck

regulator with shutdown function can be

implemented with minimum external components.

The RT9226A provides current-limit protection by

monitoring the voltage drop across N-channel

MOSFET in over current condition, therefore,

eliminates the current sensing resistor and minimizes

the efficiency loss. The soft start function reduces the

stress on power supply and components in power on

duration. The 200 kHz operating frequency and high

speed PWM control loop with Synchronous N-

channel MOSFET driver provide optimized

compromise between efficiency, cost, and response

speed. Other features include output voltage

monitoring for power good indication and over

voltage protection.

Ordering Information

RT9226A-



Package type

S : SOP-14

Operating temperature range

C: Commercial standard

Features

z

Synchronous N-channel MOSFET Driver

z

High Efficiency

z

Fast Response with 200kHz Operating

Frequency

z

Adjustable Current Limit by Sensing MOSFET

r

, without Extra Current Sensing

DS(ON)

Resistor

z

Shutdown Function

z

Power Good Indication Output and Over-

voltage Protection

Applications

Low Cost CPU Power Supply

z

Motherboard I/O Power Supply

z

Add-On Card Power Supply

z

DDR SDRAM Bus Terminator Power Supply

z

Pin Configurations

Part Number Pin Configurations

RT9226ACS

(Plastic SOP-14)

VSEN

OCSET

SS

FB

EN

GND

PGNDH

1

2

3

4

5

6

7

TOP VIEW

14

13

12

11

10

9

8

VCC

LGATE
PGNDL

BOOT

UGATE

PHASE
PGOOD

DS9226A-03 July 2000 www.richtek-ic.com.tw

1

RT9226A

Absolute Maximum Ratings

Supply Voltage 15V

z

Input, Output or I/O Voltage GND–0.3V to Vcc+0.3V

z

Ambient Temperature Range 0°C to 70°C

z

Operating Junction Temperature Range 0°C to 125°C

z

Storage Temperature Range −65°C to 150°C

z

Package Thermal Resistance

z

SOP-14, θ

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

z

Electrical Characteristics

(V

= 12V, GND = 0V, TA = 25°C, unless otherwise specified)

CC

VCC Supply Current

160°C/W

JA

Parameter Symbol Test Conditions Min Typ Max Units

Nominal Supply Current

I

CC

UGATE Open

--

3--mA

Power-On Reset

VCC Rising Threshold V

VCC Falling Threshold V

Enable Input Threshold

V

EN

OCSET

OCSET

= 4.5V

= 4.5V

-- 9.5 -- V

-- 7.5 -- V

0.2 -- 2.2 V

Oscillator

Frequency 170 200 230

Ramp Amplitude

∆V

OSC

Internal Voltage Reference

Reference Voltage

V

REF

PWM Controller Error Amplifier

DC Gain -- 65 --

PWM Controller Gate Driver

UGATE Source

UGATE Sink

LGATE Source

LGATE Sink

R

UGATEIUGATE

R

UGATEIUGATE

I

LGATEVCC

R

LGATEILGATE

= 0.3A

= 0.3A

= 12V, V

= 1V

LGATE

= 6V

Protection

-- 1.9 --

1.225 1.250 1.275

-- 8 --

-- 6 --

-- 500 --

-- 5 --

KHz

V

V

dB

Ω

Ω

mA

Ω

OCSET Sink Current

SS Current

I

OCSETVOCSET

I

SS

VSS = 1.5V

= 4.5V

Over-voltage Trip (VSEN/VREF) -- 115 120

170 200 230

-- 10 --

µA

µA

%

To be continued

www.richtek-ic.com.tw DS9226A-03 July 2000

2