G768D 查看數據表（PDF） - Global Mixed-mode Technology Inc

零件编号

产品描述 (功能)

生产厂家

G768D

Two Remote Temperature Sensors and One Fan Controller with SMBus Serial Interface and System Reset Circuit

Global Mixed-mode Technology Inc 

Global Mixed-mode Technology Inc.

Pin Description

G768D

PIN NAME

FUNCTION

1 FANVCC Output connected to VCC of fan.

2,15

VCC Supply Voltage Input, 4.5V to 5.5V. Bypass to GND with a 0.1µF capacitor.

Combined Current Source and A/D Positive Input for remote-diode channel 1. Do not leave DXP1 floating;

3

DXP1 tie DXP1 to DXN if no remote diode on channel 1 is used. Place a 2200pF capacitor between DXP1 and

DXN for noise filtering.

Combined Current Sink and A/D Negative Input. DXN is common negative node of both remote diodes on

4

DXN

channel 1 and 2. The traces of DXP1-DXN and DXP2-DXN pairs should be routed independently. The

common DXN should be connected together as close as possible to the IC. DXN is internally connected to

the GND pin for signal ground use.

Combined Current Source and A/D Positive Input for remote-diode channel 2. Do not leave DXP2 floating;

5

DXP2 tie DXP2 to DXN if no remote diode on channel 2 is used. Place a 2200pF capacitor between DXP2 and

DXN for noise filtering.

6

RESET RESET Output remains low while VCC is below the reset threshold, and for 340ms after VCC rises above

the reset threshold.

7

DGND Digital Ground.

8

AGND Analog Ground.

9

CLK 32.768KHz clock input for fan controller.

10

FG Fan pulse input.

11

ALERT SMBus Alert (interrupt) Output, open drain.

12 SMBDATA SMBus Serial-Data Input / Output, open drain.

13

NC

14 SMBCLK SMBus Serial-Clock Input.

16 TH_SHUT Thermal Shutdown Output, push-pull output.

Detailed Description

The G768D (patents pending) is a 3-in-1 IC. It consists

of one temperature sensor, 1 fan speed controller and

provides system-reset function.

The temperature sensor is designed to work in con-

junction with an external micro-controller (µC) or other

intelligence in thermostatic, process-control, or moni-

toring applications. The µC is typically a powerman-

agement or keyboard controller, generating SMBus se-

rial commands by "bit-banging" general-purpose in-

put-output (GPIO) pins or via a dedicated SMBus inter-

face block.

Essentially a 12-bit serial analog-to-digital converter

(ADC) with a sophisticated front end, the G768D con-

tains a switched current source, a multiplexer, an ADC,

an SMBus interface, one fan controller, a reset circuit

and associated control logic (Figure 1).

Temperature data from the ADC is loaded into two

data registers, where it is automatically compared with

data previously stored in four over/under-temperature

alarm registers.

ADC and Multiplexer

The ADC is an averaging type that integrates over a

60ms period (each channel, typical).

The multiplexer automatically steers bias currents

through two remote diodes, measures their forward

voltages, and computes their temperatures. All chan-

nels are converted automatically once the conversion

process has started, either in free-running or sin-

gle-shot mode. If one of the two channels is not used,

the device still performs all measurements, and the

user can simply ignore the results of the unused

channel. If the remote diode channel is unused, tie

DXPx to DXN rather than leaving the pins open.

The DXN input is internally connected to the ground

node inside the chip to set up the analog to digital

(A/D) inputs for a differential measurement. The

worst-case DXP-DXN differential input voltage range

is 0.25V to 0.95V.

Excess resistance in series with the remote diode causes

about +1/2°C error per ohm. Likewise, 200µV of offset

voltage forced on DXP-DXN causes about 1°C error.

Ver: 1.2

Apr 03, 2002

TEL: 886-3-5788833

http://www.gmt.com.tw

5

Share Link: