Ver: 2.7

Dec 26, 2005

TEL: 886-3-5788833

http://www.gmt.com.tw

4

G751

Global Mixed-mode Technology Inc.

Logic Electrical Characteristics

Temperature-to-Digital Transfer Function (Non-linear scale for clarity)

Functional Description

The

G751

temperature

sensor

incorporates

a

band-gap type temperature sensor and 9-bit ADC

(Delta-Sigma Analog- to-Digital Converter). The tem-

perature data output of the G751 is available at all

times via the SMBus. If a conversion is in progress, it

will be stopped and restarted after the read. A digital

comparator is also incorporated that compares a se-

ries

of

readings,

the

number

of

which

is

user-selectable, to user-programmable setpoint and

hysteresis values. The comparator trips the O.S. out-

put line, which is programmable for mode and polarity.

In Comparator mode the O.S. Output behaves like a

thermostat. The output becomes active when tem-

limit. In this mode the O.S. output can be used to

turn a cooling fan on, initiate an emergency system

shutdown, or reduce system clock speed. Shutdown

mode does not reset O.S. state in a comparator

mode.

active but O.S. will remain active indefinitely until

reset by reading any register via the SMBus inter-

then reset, it can activated again only by Tempera-

indefinitely until being reset by a read. Placing the

G751 in shutdown mode also resets the O.S. output.

Default Modes

G751 always powers up in a known state. G751

power up default conditions are:

1. Comparator mode

4. O.S. active low

5. Pointer set to “00”; Temperature Register

With these operating conditions G751 can act as a

stand-alone thermostat with the above temperature

settings. Connection to an SMBus is not required.

SMBus Interface

The G751 op erates as a slave on the SMBus, so

the SMBCLK line is an input (no clock is generated

by

the

G751)

and

the

SMBDATA

line

is

a

bi-directional serial data path. According to SMBus

specifications, the G751 has a 7-bit slave address.

The four most significant bits of the slave address

are hard wired inside the G751 and are “1001”. The

three least significant bits of the address are as-

signed to pins A2-A0, and are set by connecting

these pins to ground for a low, (0); or to +Vs for a

high, (1).

Therefore, the complete slave address is:

1

0

0

1

A2

A1

A0

MSB

LSB

0,1111,1010

+125°C

-55°C

-25°C

-0.5°C

0°C

+0.5°C

+25°C

Temperature

0,0011,0010

0,0000,0001

0,0000,0000

1,1111,1111

1,1100,1110

1,1001,0010

0,1111,1010

+125°C

-55°C

-25°C

-0.5°C

0°C

+0.5°C

+25°C

Temperature

0,0011,0010

0,0000,0001

0,0000,0000

1,1111,1111

1,1100,1110

1,1001,0010