G768B View Datasheet(PDF) - Global Mixed-mode Technology Inc

Part Name

Description

Manufacturer

G768B

Remote/Local Temperature Sensor, 2 Fan Controllers with SMBus Serial Interface and System Reset Circuit

Global Mixed-mode Technology Inc 

Global Mixed-mode Technology Inc.

G768B

It uses pulse width modulation (PWM) method and an

on-chip MOSFET to control the fan speed to ±2% of

the programmed speed.

The desired fan speed is also programmed via

SMBusTM. The actual fan speed and fan status can be

read via the SMBusTM. Short-circuit protection is im-

plemented to prevent damages to the fan and this IC

itself. The G768B also turns on the fans by hardware

watchdog system. The fan controller would fully turn

on both fans when one of the following conditions

happens.

1.when either of the remote temperature is higher than

its own TMAX.

2.when either of these two remote diodes is open.

3.when both remote diodes are short

The G768B also contains a microprocessor (µP) su-

pervisory circuit used to monitor the power supplies in

µP and digital systems. They provide excellent circuit

reliability and low cost by eliminating external compo-

nents and adjustments when used with 5V-powered

circuits. This circuit asserts a reset signal whenever

the VCC supply voltage declines below a preset

threshold, keeping it asserted for at least 140ms after

VCC has risen above the reset threshold. The G768B

has an active-low RESET output. The reset com-

parator is designed to ignore fast transients on VCC.

Reset threshold of this circuit is set to 4.38V.

The G768B is available in a small, 16-pin SSOP sur-

face-mount package.

Typical Operating Circuit

10µF

IN

FAN1

FG

OUT1

FG1

OUT2

FG2

10µF

IN

FAN2

FG

VCC

10µF

10µF

VCC

2N3904

DXP1

2200pF

DXN

G768B

SMBCLK

SMBDATA

ALERT

10k EACH

SMBCLK

SMBDATA

INTERRUPT TO µC

2N3904

DXP2

2200pF

CLK

CLOCK 32.768kHz

RESET

µP

RESET

GND

Ver 1.3

Oct 28, 2002

TEL: 886-3-5788833

http://www.gmt.com.tw

2

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