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PDF G767 Data sheet ( Hoja de datos )

Número de pieza G767
Descripción Remote/Local Temperature Sensor
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No Preview Available ! G767 Hoja de datos, Descripción, Manual

Global Mixed-mode Technology Inc.
G767
Remote/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:
±2°C (+60°C to + 100°C, local)
±3°C (-40°C to +125°C, local)
±3°C (+60°C to +100°C, remote)
„ 3µA (typ) Standby Supply Current
„ 70µA (max) Supply Current in Auto- Convert
Mode
„ +3V to +5.5V Supply Range
„ Small, 16-Pin SSOP Package
Applications
Desktop and Notebook
Computers
Smart Battery Packs
LAN Servers
Industrial Controls
Central Office
Telecom Equipment
Test and Measurement
Multi-Chip Modules
Pin Configuration
General Description
The G767 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 ±3°C for multiple
transistor manufacturers, with no calibration needed.
The remote channel can also measure the die tem-
perature of other ICs, such as microprocessors, that
contain an on-chip, diode-connected transistor.
The 2-wire serial interface accepts standard System
Management Bus (SMBusTM) Write Byte, Read Byte,
Send Byte, and Receive Byte commands to program
the alarm thresholds and to read temperature data.
The data format is 7 bits plus sign, with each bit cor-
responding to 1°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 G767 is available in a small, 16-pin SSOP sur-
face-mount package.
Ordering Information
ORDER ORDER NUMBER
NUMBER (Pb free)
TEMP.
RANGE
PACKAGE
G767
G767f
-55°C to +125°C SSOP-16
Typical Operating Circuit
N.C. 1
Vcc 2
DXP 3
DXN 4
N.C. 5
ADD1 6
GND 7
GND 8
G767
SSOP-16
16 N.C
15 STBY
14 SMBCLK
13 N.C.
12 SMBDATA
11 ALERT
10 ADD0
9 N.C.
0.1 µF
3V TO 5.5V
200Ω
2N3904
Vcc STBY
DXP
DXN
2200pF
SMBCLK
SMBDATA
ALERT
ADD0 ADD1 GND
10k EACH
CLOCK
DATA
INTERRUPT
TO µC
Ver: 2.5
Dec 14, 2004
TEL: 886-3-5788833
http://www.gmt.com.tw
1

1 page




G767 pdf
Global Mixed-mode Technology Inc.
G767
VCC
DXP
DXN
MUX
+
REMOTE
+ LOCAL
+ ADC
DIODE
FAULT
STBY ADD0 ADD1
2
CONTROL
LOGIC
ADDRESS
DECODER
7
SMBUS
READ WRITE
88
SMBDATA
SMBCLK
8 REMOTE TEMPERATURE
DATA REGISTER
LOCAL EMPERATURE
DATA REGISTER
8
COMMAND BYTE
(INDEX) REGISTER
ALERT
8
HIGH-TEMPETATURE
THRESHOLD (REMOTEHIGH)
LOW-TEMPETATURE
THRESHOLD (REMOTELOW)
DIGITAL COMPARATOR
(REMOTE)
QS
R
HIGH-TEMPETATURE
THRESHOLD (LOCALTHIGH)
8
LOW-TEMPETATURE
THRESHOLD (LOCAL TLOW)
8
DIGITAL COMPARATOR
(LOCAL)
SELECTED VIA
SLAVE ADD = 0001 100
STATUS BYTE
REGISTER
CONFIGURATION
BYTE REGISTER
CONVERSION RATE
REGISTER
ALERT RESPONSE
ADDRESS REGISTER
Figure 1. Functional Diagram
A/D Conversion Sequence
If a Start command is written (or generated automati-
cally in the free-running auto-convert mode), both
channels are converted, and the results of both meas-
urements are available after the end of conversion. A
BUSY status bit in the status byte shows that the de-
vice is actually performing a new conversion; however,
even if the ADC is busy, the results of the previous
conversion are always available.
Remote-Diode Selection
Temperature accuracy depends on having a
good-quality, diode-connected small-signal transistor.
Accuracy has been experimentally verified for all of the
devices listed in Table 1. The G767 can also directly
measure the die temperature of CPUs and other inte-
grated circuits having on-board temperature-sensing
diodes.
The transistor must be a small-signal type with a rela-
tively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage
must be greater than 0.25V at 10µA; check to ensure
this is true at the highest expected temperature. The
forward voltage must be less than 0.95V at 100µA;
check to ensure this is true at the lowest expected
temperature. Large power transistors don’t work at all.
Also, ensure that the base resistance is less than
100. Tight specifications for forward-current gain
(+50 to +150, for example) indicate that the manufac-
turer has good process controls and that the devices
have consistent VBE characteristics.
Thermal Mass and Self-Heating
Thermal mass can seriously degrade the G767’s ef-
fective accuracy. The thermal time constant of the
SSOP-16 package is about 140sec in still air. For the
G767 junction temperature to settle to within +1°C
after a sudden +100°C change requires about five
time constants or 12 minutes. The use of smaller
packages for remote sensors, such as SOT23s, im-
proves the situation. Take care to account for thermal
gradients between the heat source and the sensor,
and ensure that stray air currents across the sensor
package do not interfere with measurement accuracy.
Ver: 2.5
Dec 14, 2004
TEL: 886-3-5788833
http://www.gmt.com.tw
5

5 Page





G767 arduino
Global Mixed-mode Technology Inc.
Table 7. Conversion-Rate Control Byte
G767
DATA
00h
01h
02h
03h
04h
05h
06h
07h
08h to FFh
CONVERSION RATE (Hz)
0.0625
0.125
0.25
0.5
1
2
4
8
RFU
AVERAGE SUPPLY CURRENT (µA TYP, at Vcc = 3.3V)
30
33
35
48
70
128
225
425
-
Table 8. RLTS and RRTE Temp Register Update Timing Chart
OPERATING MODE
CONVERSION
INITIATED BY:
NEW CONVERSION RATE TIME UNTIL RLTS AND
(CHANGED VIA WRITE TO WCRW) RRTE ARE UPDATED
Auto-Convert
Power-on reset
N/A (0.25Hz)
156ms max
Auto-Convert
1-shot command, while idling be-
tween automatic conversions
N/A
156ms max
Auto-Convert
1-shot command
ing a conversion
that
occurs
dur- N/A
When current conversion is
complete (1-shot is ignored)
Auto-Convert
Auto-Convert
Auto-Convert
Auto-Convert
Rate timer
Rate timer
Rate timer
Rate timer
0.0625Hz
0.125Hz
0.25Hz
0.5Hz
20sec
10sec
5sec
2.5sec
Auto-Convert
Auto-Convert
Auto-Convert
Auto-Convert
Hardware Standby
Rate timer
Rate timer
Rate timer
Rate timer
STBY pin
1Hz
2Hz
4Hz
8Hz
N/A
1.25sec
625ms
312.5ms
237.5ms
156ms
Software Standby
Software Standby
RUN/STOP bit
1-shot command
N/A
N/A
156ms
156ms
To check for internal bus collisions, read the status
byte. If the least significant seven bits are ones, dis-
card the data and read the status byte again. The
status bits LHIGH, LLOW, RHIGH, and RLOW are
refreshed on the SMBus clock edge immediately fol-
lowing the stop condition, so there is no danger of los-
ing temperature-related status data as a result of an
internal bus collision. The OPEN status bit (diode con-
tinuity fault) is only refreshed at the beginning of a
conversion, so OPEN data is lost. The ALERT in-
terrupt latch is independent of the status byte register,
so no false alerts are generated by an internal bus
collision.
When auto-converting, if the THIGH and TLOW limits
are close together, it’s possible for both high-temp and
low-temp status bits to be set, depending on the
amount of time between status read operations (espe-
cially when converting at the fastest rate). In these
circumstances, it’s best not to rely on the status bits to
indicate reversals in long-term temperature changes
and instead use a current temperature reading to es-
tablish the trend direction.
Conversion Rate Byte
The conversion rate register (Table 7) programs the
time interval between conversions in free-running
auto-convert mode. This variable rate control reduces
the supply current in portable-equipment applications.
The conversion rate byte’s POR state is 02h (0.25Hz).
The G767 looks only at the 3 LSB bits of this register,
so the upper 5 bits are “don’t care” bits, which should
be set to zero. The conversion rate tolerance is ±25%
at any rate setting.
Ver: 2.5
Dec 14, 2004
TEL: 886-3-5788833
http://www.gmt.com.tw
11

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