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PDF G766 Data sheet ( Hoja de datos )
| Número de pieza | G766 | |
| Descripción | Remote Temperature Sensor with SMBus Serial Interface | |
| Fabricantes | ETC | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de G766 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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Global Mixed-mode Technology Inc.
G766
Remote Temperature Sensor with SMBus Serial
Interface
Features
Single Channel: Measures Remote CPU Tem-
perature
No Calibration Required
SMBus 2-Wire Serial Interface
Programmable Under/Overtemperature Alarms
Supports SMBus Alert Response
Accuracy:
±3°C (+60°C to +100°C, remote)
3µA (typ) Standby Supply Current
300µA (max) Supply Current in Auto- Convert
Mode
+3V to +5.5V Supply Range
Small, 10-Pin MSOP 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 G766 is a precise digital thermometer that reports
the temperature of a remote sensor. The remote sen-
sor is a diode-connected transistor typically a low-cost,
easily mounted 2N3904 NPN type-that replace con-
ventional thermistors or thermocouples. Remote ac-
curacy is ±3°C for multiple transistor manufacturers,
with no calibration needed. The G766 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 (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 twos-complement format. Meas-
urements can be done automatically and autono-
mously, 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 sup-
ply-current drain.
The G766 is available in a small, 10-pin MSOP sur-
face-mount package.
Ordering Information
PART*
G766
TEMP. RANGE
-55°C to +125°C
PIN PACKAGE
10-MSOP
Typical Operating Circuit
ADD0 1
ADD1 2
GND 3
DXN 4
DXP 5
G766
10 ALERT
9 SMBDATA
8 SMBCLK
7 STBY
6 Vcc
2N3904
10 Pin MSOP
0.1 µF
3V TO 5.5V
200Ω
Vcc STBY
DXP
DXN
2200pF
SMBCLK
SMBDATA
ALERT
ADD0 ADD1 GND
10k EACH
CLOCK
DATA
INTERRUPT
TO µC
Ver 1.0
Dec 11, 2001
TEL: 886-3-5788833
http://www.gmt.com.tw
1
1 page  
Global Mixed-mode Technology Inc.
DXP
DXN
ALERT
VCC
MUX
+
REMOTE
+ LOCAL
+ ADC
DIODE
FAULT
8 REMOTE TEMPERATURE
DATA REGISTER
8
HIGH-TEMPETATURE
THRESHOLD (REMOTE HIGH)
LOW-TEMPETATURE
THRESHOLD (REMOTE LOW)
DIGITAL COMPARATOR
(REMOTE)
STBY ADD0 ADD1
2
CONTROL
LOGIC
ADDRESS
DECODER
7
SMBUS
READ WRITE
88
COMMAND BYTE
(INDEX) REGISTER
STATUS BYTE
REGISTER
CONFIGURATION
BYTE REGISTER
CONVERSION RATE
REGISTER
QS
R
SELECTED VIA
SLAVE ADD = 0001 100
ALERT RESPONSE
ADDRESS REGISTER
G766
SMBDATA
SMBCLK
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 G766 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
100Ω. 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.
Ver 1.0
Dec 11, 2001
TEL: 886-3-5788833
http://www.gmt.com.tw
5
5 Page 
Global Mixed-mode Technology Inc.
Table 7. Conversion-Rate Control Byte
G766
DATA
00h
01h
02h
03h
04h
05h
06h
07h
08h to FFh
CONVERSION RATE (Hz)
0.0125
0.25
0.5
1
2
4
8
16
RFU
To check for internal bus collisions, read the status byte. If
the least significant seven bits are ones, discard the data
and read the status byte again. The status bits RHIGH,
and RLOW are refreshed on the SMBus clock edge im-
mediately following the stop condition, so there is no dan-
ger of losing 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 conver-
sion, so OPEN data is lost. The ALERT interrupt 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 (especially 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 cur-
rent temperature reading to establish 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 07h (16Hz).
Slave Addresses
The G766 appears to the SMBus as one device hav-
ing a common address for both ADC channels. The
device address can be set to one of nine different val-
ues by pin-strapping ADD0 and ADD1 so that more
than one G766 can reside on the same bus without
address conflicts (Table 8).
The address pin states are checked at POR only, and
the address data stays latched to reduce quiescent
supply current due to the bias current needed for
high-Z state detection.
The G766 also responds to the SMBus Alert Re-
sponse slave address (see the Alert Response Ad-
dress section).
POR and UVLO
The G766 has a volatile memory. To prevent ambigu-
ous power-supply conditions from corrupting the data
in memory and causing erratic behavior, a POR volt-
age detector monitors Vcc and clears the memory if
Vcc falls below 1.7V (typical, see Electrical Character-
istics table). When power is first applied and Vcc
rises above 1.75V (typical), the logic blocks begin op-
erating, although reads and writes at VCC levels below
3V are not recommended. A second Vcc comparator,
the ADC UVLO comparator, prevents the ADC from
converting until there is sufficient headroom (Vcc =
2.8V typical).
Table 8. Slave Address Decoding
(ADD0 and ADD1)
ADD0
ADD1
ADDRESS
GND
GND
0011 000
GND
High-Z
0011 001
GND
Vcc
0011 010
High-Z
GND
0101 001
High-Z
High-Z
0101 010
High-Z
Vcc
0101 011
Vcc GND
1001 100
Vcc High-Z
1001 101
Vcc Vcc
1001 110
Note: High-Z means that the pin is left unconnected
and floating.
Power-Up Defaults:
Interrupt latch is cleared.
Address select pins are sampled.
THIGH and TLOW registers are set to max and min
limits, respectively.
Device is in normal mode. ( ALERT acts as a
latched interrupt output.)
Ver 1.0
Dec 11, 2001
TEL: 886-3-5788833
http://www.gmt.com.tw
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet G766.PDF ] | |
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