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Global Mixed-mode Technology Inc.
G781
±1°C Remote and Local Temperature Sensor with
SMBus Serial Interface
Features
Two Channels: Measures Both Remote and
Local Temperatures
No Calibration Required
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 SO Package
Applications
Desktop and Notebook
Computers
Smart Battery Packs
LAN Servers
Industrial Controllers
Central Office
Telecom Equipment
Test and Measurement
Multi-Chip Modules
Pin Configuration
General Description
The G781 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
transistor typically a low-cost, easily mounted 2N3904
NPN type that replace conventional thermistors or
thermocouples. Remote accuracy is ±1°C with no cali-
bration needed. The remote channel can also meas-
ure the die temperature of other ICs, such as micro-
processors, 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 G781 is available in a small, 8-pin SOP sur-
face-mount package.
Ordering Information
PART*
G781
TEMP. RANGE
-20°C to +120°C
PIN-PACKAGE
8-SOP
Typical Operating Circuit
VCC 1
G781
8 SMBCLK
DXP 2
7 SMBDATA
DXN 3
6 ALERT
THERM 4
5 GND
8 Pin SOP
2N3904
0.1µF
3V TO 5.5V
VCC
DXP
SMBCLK
SMBDATA
DXN
2200pF
ALERT
THERM
GND
10kΩ EACH
CLOCK
DATA
INTERRUPT TO µC
Ver: 1.0
Oct 02, 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
1
Global Mixed-mode Technology Inc.
G781
Absolute Maximum Ratings
VCC to GND………….….……..………….-0.3V to +6V
DXP to GND……….……………..…-0.3V to VCC + 0.3V
DXN to GND……………..……………..-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT to GND..…-0.3V to +6V
SMBDATA, ALERT Current………….-1mA to +50mA
DXN Current……………………..………………….±1mA
ESD Protection (SMBCLK, SMBDATA, ALERT , human
body model).……………………………………….2000V
ESD Protection (other pins, human body model)..2000V
Continuous Power Dissipation (TA = +70°C) ..SOP
(derate 8.30mW/°C above +70°C)…………......667mW
Operating Temperature Range………-20°C to +120°C
Junction Temperature………………….………..+150°C
Storage temperature Range………….-65°C to +165°C
Lead Temperature (soldering, 10sec)……..……...+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the opera-
tional sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
Electrical Characteristics
(VCC = + 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
Temperature Error, Remote Di-
ode (Note 1)
Temperature Error, Local Diode
Supply-Voltage Range
TR = +60°C to +100°C, VCC = 3.0V to 3.6V
TR = 0°C to +125°C (Note 2)
TA = +60°C to +100°C
TA = 0°C to +85°C (Note 2)
Undervoltage Lockout Threshold VCC input, disables A/D conversion, rising edge
Undervoltage Lockout Hysteresis
Power-On Reset Threshold
VCC, falling edge
POR Threshold Hysteresis
Standby Supply Current
Logic inputs forced to VCC or GND
SMBus static
Hardware or software
standby, SMBCLK at 10kHz
Average Operating Supply
Current
Auto-convert mode. Logic inputs
forced to VCC or GND
0.5 conv/sec
8.0 conv/sec
Conversion Time
From stop bit to conversion complete (both channels)
Conversion Rate Timing
Conversion-Rate Control Byte=04h, 1Hz
Remote-Diode Source Current DXP forced to 1.5V
High level
Low level
MIN TYP MAX UNITS
-1 +1 °C
-3 +3
-3
-5
+3
+5
°C
3.0 5.5 V
2.8 V
50 mV
1.7 V
50 mV
3
4 µA
35
320
µA
125 ms
1 sec
176
11
µA
Ver: 1.0
Oct 02, 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
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