Global Mixed-mode Technology Inc.
G784
±1°C Remote and Local Temperature Sensor with
SMBus Serial Interface
Features
General Description
Two Channels: Measures Both Remote and
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.
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
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.
+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
Computers
Smart Battery Packs
LAN Servers
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.
Central Office
Telecom Equipment
Test and Measurement
Multi-Chip Modules
Industrial Controllers
Pin Configuration
Typical Application Circuit
3V TO 5.5V
0.1µF
G784/G784-1
G784/G784-1
VCC
SMBCLK
8
7
6
5
1
2
3
4
10kΩ EACH
VCC
VCC
DXP
DXN
SMBCLK
SMBDATA
ALERT
1
2
3
8
DXP
DXN
CLOCK
DATA
SMBDATA
ALERT
SMBCLK
DXP
DXN
7
6
5
Thermal
Pad
SMBDATA
ALERT
INTERRUPT TO µC
THERM
GND
4
2200pF
2N3904
THERM
THERM
GND
GND
TDFN3X3-8
SOP-8/MSOP-8
Note: Recommend connecting the Thermal Pad to the GND or let it keep floating.
Ver: 0.2
Oct 02, 2008
TEL: 886-3-5788833
http://www.gmt.com.tw
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