RT8100 查看數據表（PDF） - Richtek Technology

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RT8100

Synchronous buck PWM DC/DC with Dual Voltage Control Mode

Richtek Technology 

Function Block Diagram

Preliminary

RT8100

12VCC 5VSB

RT

Oscillator free Running 200kHz

SS

Soft Stsrt

CLK

POR Power_sel

EN & VIN Detection

PI

CSN

CSP

I_IND

RR

VREF

+

GM

S/H

-

x4

S/H

CLK

Ramp

Current

Generator

To RR Pin

VREF_SEL

OCP

Current to

Voltage

Converter

+

-

+

-

PWMCP

PWM

Logic

Driver

PVCC

PVCC

FB

COMP

BOOT

UGATE

PHASE

LGATE

GND

Operation

RT8100 is a highly flexible, high performance and high

precision synchronous buck controller specifically

designed for high-end graphic core power supply as well

as DDR applications, with highly reduced external

components and costs.

RT8100 uses RichTek proprietary Analogous Current

ModeTM topology which mimics the traditional peak current

mode by sensing the valley current of the inductor via DCR

sensing techniques and simulating the current ramp with

an artificial ramp set externally. The Analogous Current

Mode topology benefits all the advantages of peak current

mode converter with much higher noise immunity than

conventional one. Since the compensation is easier and

with less constraint than that in voltage mode, using low

ESR output capacitor as MLCC is possible, which therefore

dramatically reduce the board size as well as the cost and

has better transient response due to higher control

bandwidth. RT8100 also adopts VIN feedfoward for ramp

setting, which decreases the complexity for compensation

by keeping the modulator gain constant along line

variations.

The wide input voltage range of the converter ranges from

3.3V to 12V. The output voltage can be set from 0.8V to

3.3V with external resistor divider.

The power sequence of RT8100 includes :

1 : POR function

2 : VIN power supply detection

3 : PI pin setting to enable the whole chip.

The external elements selection of RT8100 includes :

1 : RT pin resister to GND to set the operation frequency

of the chip.

2 : CSN pin resister to set the current gain(ratio of

inductance current IL and sensed current Ix).

3 : RR pin resister to VIN to set the slope of the VIN feed

forward ramp and the effective slope compensation of

current mode.

4 : Use RCSN resister to set the over current level.

5 : Capacitor at SS pin to set the soft-start time.

6 : Type two compensation at COMP pin.

DS8100-03 August 2007

www.richtek.com

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