Ver: 0.2

Oct 02, 2008

TEL: 886-3-5788833

http://www.gmt.com.tw

1

Global Mixed-mode Technology Inc.

G784

±

1°C Remote and Local Temperature Sensor with

SMBus Serial Interface

Features

Two Channels: Measures Both Remote and

Local Temperatures

No Calibration Required

Built-in Noise-Buster for Remote Sensor

SMBus 2-Wire Serial Interface

Programmable Under/Overtemperature Alarms

Supports SMBus Alert Response

Accuracy:

±

1°C (+60°C to +100°C, remote)

±

3°C (+60°C to + 100°C, local)

320µA (typ) Average Supply Current During

Conversion

+3V to +5.5V Supply Range

Small 8-Lead SOP , MSOP and TDFN Package

Remote Temperature Measurment up to 160°C

by using offset shifting method (see “Measure

Remote Temperature Higher Than 127°C” sec-

tion)

SMBus Inputs with Built-in MOS Switch to Pre-

vent Reverse Current from Bus to IC VCC

Applications

Desktop and Notebook

Central Office

Computers

Telecom Equipment

Smart Battery Packs

Test and Measurement

LAN Servers

Multi-Chip Modules

Industrial Controllers

General Description

The G784 is a precise digital thermometer that reports

the temperature of both a remote sensor and its own

package. The remote sensor is a diode-connected tran-

sistor typically a low-cost, easily mounted 2N3904 NPN

type that replace conventional thermistors or thermo-

couples. Remote accuracy is ±1°C with no calibration

needed. It also has a build-in noise filtering function in

remote sensor measuring the diode temperature. The

remote channel can also measure the die temperature

of other ICs, such as microprocessors, that contain an

on-chip, diode-connected transistor.

The 2-wire serial interface accepts standard System

Management Bus (SMBus) Write Byte, Read Byte,

Send Byte, and Receive Byte commands to program

the alarm thresholds and to read temperature data.

The data format is 11bits plus sign, with each bit cor-

responding to 0.125°C, in two’s-complement format.

Measurements can be done automatically and

autonomously, with the conversion rate programmed

by the user or programmed to operate in a single-shot

mode. The adjustable rate allows the user to control

the supply current drain.

The G784 and G784-1 have the same functions but

different SMBus slave addresses. This allows for one

of each to be on the bus at the same time.

The G784 is available in a small, 8-pin SOP, MSOP

and TDFN surface-mount package.

Pin Configuration

Typical Application Circuit

THERM

DXN

8

6

5

1

2

3

4

VCC

DXP

SMBDATA

SMBCLK

GND

SOP-8/MSOP-8

G784/G784-1

7

ALERT

0.1µF

3V TO 5.5V

VCC

DXP

DXN

SMBCLK

SMBDATA

ALERT

10k

Ω EACH

CLOCK

DATA

INTERRUPT TO µC

GND

2200pF

2N3904

THERM

TDFN3X3-8

1

2

3

4

8

7

6

5

Thermal

Pad

G784/G784-1

Note: Recommend connecting the Thermal Pad to the GND or let it keep floating.

THERM

DXN

VCC

DXP

SMBDATA

SMBCLK

GND

ALERT

THERM

DXN

8

6

5

1

2

3

4

VCC

DXP

SMBDATA

SMBCLK

GND

SOP-8/MSOP-8

G784/G784-1

7

ALERT

0.1µF

3V TO 5.5V

VCC

DXP

DXN

SMBCLK

SMBDATA

ALERT

10k

Ω EACH

CLOCK

DATA

INTERRUPT TO µC

GND

2200pF

2N3904

THERM

0.1µF

3V TO 5.5V

VCC

DXP

DXN

SMBCLK

SMBDATA

ALERT

10k

Ω EACH

CLOCK

DATA

INTERRUPT TO µC

GND

2200pF

2N3904

THERM

TDFN3X3-8

1

2

3

4

8

7

6

5

Thermal

Pad

G784/G784-1

Note: Recommend connecting the Thermal Pad to the GND or let it keep floating.

THERM

DXN

VCC

DXP

SMBDATA

SMBCLK

GND

ALERT