RT9641BGS datasheet(7/11 Pages) RICHTEK

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RT9641A/B

DS9641A/B-11 March 2007

www.richtek.com

this pin to the gate of a suitable N-MOS transistor or the

base of a suitable NPN transistor.

VSEN2 (Pin 16)

Connect this pin to the memory output (VOUT2). In sleep

states, this pin is regulated to 2.5V(2.6V) or 3.3V(3.43V)

(based on RSEL) through an internal pass transistor

capable of delivering 300mA (Typically). The active-state

voltage at this pin is regulated through an external NPN

or NMOS transistor connected at the DRV2 pin for both

2.5V(2.6V) and 3.3V(3.43V) setting. During all operating

states, the voltage at this pin is monitored for under-voltage

events.

Application Information

Operation

The RT9641A/B controls 3 output voltages. It is designed

for microprocessor computer applications with 3.3V, 5V,

5VSB, and 12V outputs from an ATX power supply. The IC

is composed of two linear controllers supplying the PCI

slots

' 3.3V

AUX power (3.3VDUAL, VOUT1) and the 2.5V

RDRAM or 3.3V SDRAM memory power (2.5V/3.3V

(2.6V/3.43V) VMEM, VOUT2), and a dual switch controller

supplying the 5V

DUAL

voltage (VOUT3). In addition, all the

control and monitoring functions necessary for complete

ACPI implementation are integrated into the RT9641A/B.

Initialization

The RT9641A/B automatically initializes upon receipt of

input power. The Power-On Reset (POR) function

continually monitors the 5VSB input supply voltage,

initiating soft-start operation after it exceeds its POR

threshold (in S4/S5 states). The 5VSB POR trip event is

also used to lock in the memory voltage setting based on

RSEL.

The RT9641A/B forces the operation mode to start from

S4/S5 states at POR releasing with 3.3VDUAL and 5VDUAL

voltages under control of EN3VDL and EN5VDL input

signals.

Table 2. 5VDUAL Output (VOUT3) Truth Table

Very similarly, Table 2 details the fact that EN5VDL status

controls whether the 5VDUAL plane supports sleeps states.

EN5VDL

S5 S3 5VDL

Comments

S0, S1 States(Active)

Note

Maintains Previous State

S4/S5

S0, S1 States(Active)

Note

Maintains Previous State

S4/S5

Note: Combination not allowed.

EN3VDL S5 S3 3V3DL

Comments

3.3V

S0, S1 States (Active)

3.3V

Note

Maintains Previous State

3.3V

S4/S5

3.3V

S0, S1 States (Active)

3.3V

Note

Maintains Previous State

S4/S5

Note: Combination not allowed.

As seen in Table 1, EN3VDLsimply controls whether the

3.3VDUAL plane remains powered up during S4/S5 sleep

state.

Table 1. 3.3VDUAL Output (VOUT1) Truth Table

Operational Truth Tables

The EN3VDL and EN5VDL pins offer a host of choices in

terms of the overall system architecture and supported

features. Tables 1~3 describe the truth combinations

pertaining to each of the three outputs.

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