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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 Central Office
Computers Telecom Equipment
Smart Battery Packs Test and Measurement
LAN Servers Multi-Chip Modules
Industrial Controls
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 temperature of other ICs, such as microprocessors, that
contain an on-chip, diode-connected transistor.
The 2-wire serial interface accepts standard System
Management Bus (SMBus
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 corresponding 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 surface-mount package.
TM
) Write Byte, Read Byte,
Ordering Information
Part* Temp. range Pin-package
G767 -55°C to +125°C 16-SSOP
Pin Configuration Typical Operating Circuit
G767
N.C.
Vcc
DXP
DXN
N.C.
ADD1
GND
GND
1
2
3
4
5
6
7
8
16Pin SSOP
16
15
14
13
12
11
10
9
N.C
STBY
SMBCLK
N.C.
SMBDATA
ALERT
ADD0
N.C.
2N3904
0.1 µF
2200pF
STBY
Vcc
DXP
DXN
ADD0 ADD1 GND
SMBCLK
SMBDATA
ALERT
200
3V TO 5.5V
Ω
10k EACH
CLOCK
DATA
INTERRUPT
TO µC
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Absolute Maximum Ratings
Vcc to GND………….….……..………….-0.3V to +6V
DXP, ADD to GND……….…….…-0.3V to (Vcc + 0.3V)
DXN to GND……………..……………..-0.3V to +0.8V
SMBCLK, SMBDATA,
……………………………………………..…-0.3V to +6V
SMBDATA,
ALERT Current………….-1mA to +50mA
DXN Current……………………..………………….±1mA
ESD Protection (SMBCLK, SMBDATA,
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 operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
ALERT , STBY to GND…………
ALERT , human
body model).………………………………………..4000V
ESD Protection (other pins, human body model)..2000V
Continuous Power Dissipation (T
(derate 8.30mW/°C above +70°C)…………......667mW
Operating Temperature Range………-55°C to +125°C
Junction Temperature………………….………..+150°C
Storage temperature Range………….-65°C to +165°C
Lead Temperature (soldering, 10sec)……..……...+300°C
G767
= +70°C) SSOP
A
Electrical Characteristics
(Vcc = + 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
ADC and power supply
Temperature Resolution (Note 1) Monotonicity guaranteed 8 Bits
TA = +60°C to +100°C -2 2 Initial Temperature Error,
Local Diode (Note 2)
ode (Notes 2 and 3)
(Notes 1 and 2)
Supply-Voltage Range 3.0 5.5 V
Undervoltage Lockout Threshold Vcc input, disables A/D conversion, rising edge 2.6 2.8 2.95 V
Undervoltage Lockout Hysteresis 50 mV
Power-On Reset Threshold Vcc , falling edge 1.0 1.7 2.5 V
POR Threshold Hysteresis 50 mV
Standby Supply Current
Average Operating Supply
Current
Conversion Time From stop bit to conversion complete(both channels) 94 125 156 ms
Conversion Rate Timing Error Auto-convert mode -25 25 %
Remote-Diode Source Current
Address Pin Bias Current ADD0, ADD1; momentary upon power-on reset 160 µA
= 0°C to +85°C -3 3
T
A
TR = +60°C to +100°C -3 3 Temperature Error, Remote Di-
= -55°C to +125°C -5 5
T
R
Including long-term drift
Logic inputs forced
to Vcc or GND
Auto-convert mode,average measured over 4sec. Logic inputs forced
to Vcc or GND
DXP forced to 1.5V
TA = +60°C to +100°C -2.5 2.5 Temperature Error, Local Diode
= 0°C to +85°C -3.5 3.5
T
A
SMBus static 3 10
Hardware or software
standby, SMBCLK at 10kHz
0.25 conv/sec 35 70
2.0 conv/sec 120 180
High level 80 100 120
Low level 8 10 12
4
°C
°C
°C
µA
µA
µA
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Electrical Characteristics
(Vcc = + 3.3V, T
= 0 to +85°C, unless otherwise noted.)
A
(continued)
G767
PARAMETER CONDITIONS MIN TYP MAX UNITS
SMBus Interface
, SMBCLK, SMBDATA; Vcc = 3V to 5.5V
Logic Input High Voltage
Logic Input Low Voltage
Logic Output Low Sink Current
ALERT
Logic Input Current Logic inputs forced to Vcc or GND -1 1 µA
SMBus Input Capacitance SMBCLK, SMBDATA 5 pF
SMBus Clock Frequency (Note 4) DC 100 kHz
SMBCLK Clock Low Time t
SMBCLK Clock High Time t
SMBus Start-Condition Setup Time 4.7 µs
SMBus Repeated Start-Condition Setup Time t
SMBus Start-Condition Hold Time t
SMBus Start-Condition Setup Time t
SMBus Data Valid to SMBCLK Rising-Edge
Time
SMBus Data-Hold Time t
SMBCLK Falling Edge to SMBus Data-Valid
Time
Output High Leakage Current
STBY
, SMBCLK, SMBDATA; Vcc = 3V to 5.5V
STBY
ALERT
ALERT
t
SMBCLK
Master clocking in data 1 µs
, SMBDATA forced to 0.4V
forced to 5.5V
, 10% to 10% points 4.7 µs
LOW
, 90% to 90% points 4 µs
HIGH
90% to 90% points 500 ns
SU : STA ,
10% of SMBDATA to 90% of SMBCLK 4 µs
HD: STA ,
90% of SMBDATA to 10% of SMBDATA 4 µs
SD: STO ,
10% or 90% of SMBDATA to 10% of
SU: DAT ,
(Note 5) 0 µs
HD : DAT
2.2 V
0.8 V
6 mA
1 µA
800 ns
Electrical Characteristics
(Vcc = + 3.3V, TA = -5.5 to + 125°C, unless otherwise noted.) (Note 6)
PARAMETER CONDITIONS MIN TYP MAX UNITS
ADC and power supply
Temperature Resolution (Note 1) Monotonicity guaranteed 8 Bits
TA = +60°C to +100°C -2 2 Initial Temperature Error, Local
Diode (Note 2)
(Notds2 and 3)
Supply-Voltage Range 3.0 5.5 V
Conversion Time From stop bit to conversion complete (both channels) 94 125 156 ms
Conversion Rate Timing Error Auto-convert mode -25 25 %
SMBus Interface
Logic Input High Voltage STBY, SMBCLK, SMBDATA
Logic Input Low Voltage STBY, SMBCLK, SMBDATA; Vcc = 3V to 5.5V 0.8 V
Logic Output Low Sink Current ALERT, SMBDATA forced to 0.4V 6 mA
ALERT
Logic Input Current Logic inputs forced to Vcc or GND -2 2 µA
Note1:
Note2:
Output High Leakage Current
Guaranteed but not 100% tested.
Quantization error is not included in specifications for temperature accuracy. For example, if the G767 de-
= -55°C to +125°C -3 3
T
A
TR = +60°C to +100°C -3 3 Temperature Error, Remote Diode
= -55°C to +125°C -5 5
T
R
Vcc = 3V 2.2
Vcc = 5.5V 2.4
ALERT forced to 5.5V 1 µA
vice temperature is exactly +66.7°C, or +68°C (due to the quantization error plus the +1/2°C offset used for
rounding up) and still be within the guaranteed ±1°C error limits for the +60°C to 100°C temperature range.
See Table2.
Note3:
A remote diode is any diode-connected transistor from Table1. T
is the junction temperature of the remote
R
of the remote diode. See Remote Diode Selection for remote diode forward voltage requirements.
Note4:
The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is
possible, it violates the 10kHz minimum clock frequency and SMBus specifications, and may monopolize the bus.
Note5:
Note that a transition must internally provide at least a hold time in order to bridge the undefined region
(300ns max) of SMBCLK’s falling edge.
Note6:
Ver 2.2
Nov 07, 2001
Specifications from -55°C to +125°C are guaranteed by design, not production tested.
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°C
V
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Pin Description
PIN NAME FUNCTION
1,5,9,13,16 N.C. No Connection. Not internally connected. May be used for PC board trace routing
2 Vcc
3 DXP
4 DXN Combined Current Sink and A/D Negative Input.
6 ADD1
7,8 GND Ground
10 ADD0 SMBus Slave Address Select pin
11
12 SMBDATA SMBus Serial-Data Input / Output , open drain
14 SMBCLK SMBus Serial-Clock Input
15
ALERT
STBY
Detailed Description
The G767 (patents pending) is a temperature sensor
designed to work in conjunction with an external microcontroller (µC) or other intelligence in thermostatic,
process-control, or monitoring applications. The µC is
typically a power-management or keyboard controller,
generating SMBus serial commands by “bit-banging”
general-purpose input-output (GPIO) pins or via a
dedicated SMBus interface block.
Essentially an 8-bit serial analog-to digital converter
(ADC) with a sophisticated front end, the G767 contains a switched current source, a multiplexer, an ADC,
an SMBus interface, and associated control logic (Figure 1). Temperature data from the ADC is loaded into
two data registers, where it is automatically compared
with data previously stored in four over/under- temperature alarm registers.
ADC and Multiplexer
The ADC is an averaging type that integrates over a
Supply Voltage Input , 3V to 5.5V. Bypass to GND with a 0.1µF capacitor. A 200
recommended but not required additional noise filtering.
Combined Current Source and A/D Positive Input for remote-diode channel. Do not leave DXP floating; tie DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for
noise filtering.
SMBus Address Select pin (Table 8). ADD0 and ADD1 are sampled upon power-up. Excess capacitance (>50pF) at the address pins when floating may cause address-recognition problems.
SMBus Alert (interrupt) Output, open drain
Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode.
Low = standby mode, high = operate mode.
60ms period (each channel, typical), with excellent
noise rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes, measures their
forward voltages, and computes their temperatures.
Both channels are automatically converted once the
conversion process has started, either in free-running
or single-shot mode. If one of the two channels is not
used, the device still performs both measurements,
and the user can simply ignore the results of the unused channel. If the remote diode channel is unused,
tie DXP to DXN rather than leaving the pins open.
The worst-case DXP-DXN differential input voltage
range is 0.25V to 0.95V.
Excess resistance in series with the remote diode
causes about +1/2°C error per ohm. Likewise, 200µV
of offset voltage forced on DXP-DXN causes about
1°C error.
G767
series resistor is
Ω
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DXP
DXN
Global Mixed-mode Technology Inc.
V
CC
MUX
+
+
REMOTE
LOCAL
DIODE
FAULT
+
ADC
CONTROL
LOGIC
STBY
2
ADD0
ADDRESS
DECODER
SMBUS
READ
8
ADD1
WRITE
G767
7
SMBDATA
SMBCLK
8
REMOTE TEMPERAT URE
8
DATA REGISTER
HIGH-TEMPETATURE
8
ALERT
THRESHOLD (REMOTE
LOW-TEMPETATURE
THRESHOLD (REMOTE
DIGITAL COMPARATOR
(REMOTE)
S
Q
R
HIGH
)
)
LOW
THRESHOLD (LOCALT
THRESHOLD (LOCAL T
Figure 1. Functional Diagram
A/D Conversion Sequence
If a Start command is written (or generated automatically in the free-running auto-convert mode), both
channels are converted, and the results of both measurements are available after the end of conversion. A
BUSY status bit in the status byte shows that the device is actually performing a new conversion; however,
even if the ADC is busy, the results of the previous
conversion are always available.
LOCAL EMPERATURE
DATA REGISTER
HIGH-TEMPETATURE
LOW-TEMPETATURE
8
DIGITAL COMPARATOR
(LOCAL)
SELECTED VIA
SLAVE ADD = 0001 100
HIGH
)
)
LOW
8
8
COMMAND BYTE
(INDEX) REGISTER
STATUS BYTE
REGISTER
CONFIGURATION
BYTE REGISTER
CONVERSION RATE
REGISTER
ALERT RESPONSE
ADDRESS REGISTER
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 manufacturer has good process controls and that the devices
have consistent VBE characteristics.
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 integrated circuits having on-board temperature-sensing
diodes.
The transistor must be a small-signal type with a relatively 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
Ver 2.2
Nov 07, 2001
Thermal Mass and Self-Heating
Thermal mass can seriously degrade the G767’s effective 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, improves 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.
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Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For the local diode, the
worst-case error occurs when auto-converting at the
fastest rate and simultaneously sinking maximum cur-
rent at the
and with
pation is Vcc x 450µA plus 0.4V x 1mA. Package theta
J-A is about 150°C /W, so with Vcc = 5V and no copper
PC board heat-sinking, the resulting temperature rise is:
dT = 2.7mW x 150°C /W = 0.4°C
Even with these contrived circumstances, it is difficult
to introduce significant self-heating errors.
Table 1. Remote-Sensor Transistor Manufacturers
Philips PMBS3904
Motorola(USA) MMBT3904
National Semiconductor(USA) MMBT3904
Note:Transistors must be diode-connected (base
shorted to collector).
ADC Noise Filtering
The ADC is an integrating type with inherently good
noise rejection, especially of low-frequency signals
such as 60Hz/120Hz power-supply hum. Micropower
operation places constraints on high-frequency noise
rejection; therefore, careful PC board layout and proper external noise filtering are required for
high-accuracy remote measurements in electrically
noisy environments.
High-frequency EMI is best filtered at DXP and DXN
with an external 2200pF capacitor. This value can be
increased to about 3300pF(max), including cable capacitance. Higher capacitance than 3300pF introduces
errors due to the rise time of the switched current
source.
Nearly all noise sources tested cause the ADC measurements to be higher than the actual temperature,
typically by +1°C to 10°C, depending on the frequency
and amplitude(see Typical Operating Characteristics).
PC Board Layout
Place the G767 as close as practical to the remote
diode. In a noisy environment, such as a computer
motherboard, this distance can be 4 in. to 8 in. (typical)
or more as long as the worst noise sources (such as
CRTs, clock generators, memory buses, and ISA/PCI
buses) are avoided.
ALERT output. For example, at an 8Hz rate
ALERT sinking 1mA, the typical power dissi-
MANUFACTURER MODEL NUMBER
coils of a CRT. Also, do not route the traces across a
fast memory bus, which can easily introduce +30°C
error, even with good filtering, Otherwise, most noise
sources are fairly benign.
Route the DXP and DXN traces in parallel and in close
proximity to each other, away from any high-voltage
traces such as +12V
board contamination must be dealt with carefully,
since a 20MΩ leakage path from DXP to ground
causes about +1°C error.
Connect guard traces to GND on either side of the
DXP-DXN traces (Figure 2). With guard traces in place,
routing near high-voltage traces is no longer an issue.
Route through as few vias and crossunders as
possible to minimize copper/solder thermocouple effects.
When introducing a thermocouple, make sure that
both the DXP and the DXN paths have matching
thermocouples. In general, PC board-induced thermocouples are not a serious problem, A copper-solder
thermocouple exhibits 3µV/°C, and it takes about
200µV of voltage error at DXP-DXN to cause a +1°C
measurement error. So, most parasitic thermocouple
errors are swamped out.
Use wide traces. Narrow ones are more inductive and
tend to pick up radiated noise. The 10 mil widths and
spacing recommended on Figure 2 aren’t absolutely
necessary (as they offer only a minor improvement in
leakage and noise), but try to use them where practical.
Keep in mind that copper can’t be used as an EMI
shield, and only ferrous materials such as steel work
will. Placing a copper ground plane between the
DXP-DXN traces and traces carrying high-frequency
noise signals does not help reduce EMI.
PC Board Layout Checklist
G767
. Leakage currents from PC
DC
Place the G767 close to a remote diode.
Keep traces away from high voltages (+12V bus).
Keep traces away from fast data buses and CRTs.
Use recommended trace widths and spacing.
Place a ground plane under the traces
Use guard traces flanking DXP and DXN and con
necting to GND.
Place the noise filter and the 0.1µF Vcc bypass
capacitors close to the G767.
Add a 200Ω resistor in series with Vcc for best
noise filtering (see Typical Operating Circuit).
Do not route the DXP-DXN lines next to the deflection
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10 MILS
10 MILS
Global Mixed-mode Technology Inc.
RUN/STOP bit being high.
Activate hardware standby mode by forcing the
GND
10 MILS
DXP
MINIMUM
DXN
10 MILS
GND
STBY pin low. In a notebook computer, this line may
be connected to the system SUSTAT# suspend-state
signal.
The
STBY pin low state overrides any software conversion command. If a hardware or software standby
command is received while a conversion is in progress,
the conversion cycle is truncated, and the data from
that conversion is not latched into either temperature
reading register. The previous data is not changed and
remains available.
G767
Figure 2. Recommended DXP/DXN PC Traces
Twisted Pair and Shielded Cables
For remote-sensor distances longer than 8 in., or in
particularly noisy environments, a twisted pair is recommended. Its practical length is 6 feet to 12feet (typical) before noise becomes a problem, as tested in a
noisy electronics laboratory. For longer distances, the
best solution is a shielded twisted pair like that used
for audio microphones. Connect the twisted pair to
DXP and DXN and the shield to GND, and leave the
shield’s remote end unterminated.
Excess capacitance at DX_limits practical remote
sensor distances (see Typical Operating Characteristics), For very long cable runs, the cable’s parasitic
capacitance often provides noise filtering, so the
2200pF capacitor can often be removed or reduced in
value. Cable resistance also affects remote-sensor
accuracy; 1Ω series resistance introduces about + 1°C
error.
Low-Power Standby Mode
Standby mode disables the ADC and reduces the
supply-current drain to less than 10µA. Enter standby
mode by forcing the
RUN/STOP bit in the configuration byte register.
Hardware and software standby modes behave almost
identically: all data is retained in memory, and the
SMB interface is alive and listening for reads and
writes. The only difference is that in hardware standby
mode, the one-shot command does not initiate a
conversion.
Standby mode is not a shutdown mode. With activity
on the SMBus, extra supply current is drawn (see
Typical Operating Characteristics). In software
standby mode, the G767 can be forced to perform A/D
conversions via the one-shot command, despite the
STBY pin low or via the
Supply-current drain during the 125ms conversion
period is always about 450µA. Slowing down the conversion rate reduces the average supply current (see
Typical Operating Characteristics). In between conversions, the instantaneous supply current is about
25µA due to the current consumed by the conversion
rate timer. In standby mode, supply current drops to
about 3µA. At very low supply voltages (under the
power-on-reset threshold), the supply current is higher
due to the address pin bias currents. It can be as high
as 100µA, depending on ADD0 and ADD1 settings.
SMBus Digital Interface
From a software perspective, the G767 appears as a
set of byte-wide registers that contain temperature
data, alarm threshold values, or control bits, A standard SMBus 2-wire serial interface is used to read
temperature data and write control bits and alarm
threshold data.
Each A/D channel within the device responds to the
same SMBus slave address for normal reads and
writes.
The G767 employs four standard SMBus protocols:
Write Byte, Read Byte, Send Byte, and Receive Byte
(Figure 3). The shorter Receive Byte protocol allows
quicker transfers, provided that the correct data register was previously selected by a Read Byte instruction.
Use caution with the shorter protocols in multi-master
systems, since a second master could overwrite the
command byte without informing the first master.
The temperature data format is 7bits plus sign in
twos-complement form for each channel, with each
data bit representing 1°C (Table 2), transmitted MSB
first. Measurements are offset by +1/2°C to minimize
internal rounding errors; for example, +99.6°C is reported as +100°C.
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Write Byte Format
S ADDRESS WR
7 bits 8 bits 8 bits 1
Slave Address:
Command Byte:
Data byte:
equivalent to chip- select line of a 3-wire interface
selects which register you are writing to
data goes into the register set by the command byte (to set thresholds, configuration masks, and sam
pling rate)
ACK COMMAND ACK DATA ACK P
G767
Read Byte Format
S ADDRESS WR
7 bits 8bits 7bits 8 bits
Slave Address:
Command Byte:
Slave Address:
Data byte:
reads from the register set by the command byte
ACK COMMAND ACK S ADDRESS RD ACK DATA /// P
equivalent to chip- select line
selects which register you are reading from
repeated due to change in data-flow direction
Send Byte Format
S ADDRESS WR
7 bits 8 bits
Command Byte:
sends command with no data , usually used for one-shot command
ACK COMMAND ACK P
Receive Byte Format
S ADDRESS RD
7 bits 8 bits
Data Byte:
reads data from the register commanded by the last Read Byte or Write Byte transmission; also used
for SMBus Alert Response return address
ACK DATA /// P
S = Start condition Shaded = Slave transmission P = Stop condition /// = Not acknowledged
Figure 3. SMBus Protocols
Table 2. Data Format (Twos-Complement)
TEMP.
(°C)
+130.00 +127 0 111 1111
+127.00 +127 0 111 1111
+126.50 +127 0 111 1111
+126.00 +126 0 111 1110
+25.25 +25 0 001 1001
+0.50 +1 0 000 0001
+0.25 +0 0 000 0000
+0.00 +0 0 000 0000
-0.25 +0 0 000 0000
-0.50 +0 0 000 0000
-0.75 -1 1 111 1111
-1.00 -1 1 111 1111
-25.00 -25 1 110 0111
-25.50 -25 1 110 0110
-54.75 -55 1 100 1001
-55.00 -55 1 100 1001
-65.00 -65 1 011 1111
-70.00 -65 1 011 1111
ROUND
TEMP.
(°C)
DIGITAL OUTPUT
DATA BITS
SIGN MSB LSB
Alarm Threshold Registers
Four registers store alarm threshold data, with
high-temperature (T
) and low-temperature (T
HIGH
registers for each A/D channel. If either measured
temperature equals or exceeds the corresponding
alarm threshold value, an
ALERT interrupt is as-
serted.
The power-on-reset (POR) state of both T
is full scale (0111 1111, or +127°C). The POR state of
both T
registers is 1100 1001 or -55°C.
LOW
Diode Fault Alarm
There is a continuity fault detector at DXP that detects
whether the remote diode has an open-circuit condition. At the beginning of each conversion, the diode
fault is checked, and the status byte is updated. This
fault detector is a simple voltage detector; if DXP rises
above V
– 1V (typical) due to the diode current
CC
source, a fault is detected. Note that the diode fault
isn’t checked until a conversion is initiated, so immediately after power-on reset the status byte indicates no
fault is present, even if the diode path is broken.
HIGH
LOW
registers
)
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If the remote channel is shorted (DXP to DXN or DXP
to GND), the ADC reads 0000 0000 so as not to trip
either the T
In applications that are never subjected to 0°C in normal operation, a 0000 0000 result can be checked to
indicate a fault condition in which DXP is accidentally
short circuited. Similarly, if DXP is short circuited to
V
, the ADC reads +127°C for both remote and local
CC
channels, and the device alarms.
Table 3. Read Format for Alert Response Address
BIT NAME FUNCTION
7(MSB) ADD7
6 ADD6
5 ADD5
4 ADD4
3 ADD3
2 ADD2
1 ADD1
0(LSB) 1 Logic 1
ALERT Interrupts
ALERT interrupt output signal is latched and
The
can only be cleared by reading the Alert Response
address. Interrupts are generated in response to T
or T
HIGH
(0001 100)
alarms at their POR settings.
LOW
Provide the current G767
slave address that was
latched at POR (Table 8)
HIGH
G767
and T
disconnected (for continuity fault detection). The interrupt does not halt automatic conversions; new temperature data continues to be available over the
SMBus interface after
terrupt output pin is open-drain so that devices can
share a common interrupt line. The interrupt rate can
never exceed the conversion rate.
The interface responds to the SMBus Alert Response
address, an interrupt pointer return-address feature
(see Alert Response Address section). Prior to taking
corrective action, always check to ensure that an interrupt is valid by reading the current temperature.
Alert Response Address
The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Upon receiving an
the host master can broadcast a Receive Byte transmission to the Alert Response slave address (0001
100). Then any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus (Table 3).
comparisons and when the remote diode is
LOW
ALERT is asserted. The in-
ALERT interrupt signal,
Table 4. Command-Byte Bit Assignments
REGISTER COMMAND POR STATE FUNCTINON
RLTS 00h 0000 0000* Read local temperature: returns latest temperature
RRTE 01h 0000 0000* Read remote temperature: returns latest temperature
RSL 02h N/A Read status byte (flags, busy signal)
RCL 03h 0000 0000 Read configuration byte
RCRA 04h 0000 0010 Read conversion rate byte
RLHN 05h 0111 1111 Read local T
RLLI 06h 1100 1001 Read local T
RRHI 07h 0111 1111 Read remote T
RRLS 08h 1100 1001 Read remote T
WCA 09h N/A Write configuration byte
WCRW 0Ah N/A Write conversion rate byte
WLHO 0Bh N/A Write local T
WLLM 0Ch N/A Write local T
WRHA 0Dh N/A Write remote T
WRLN 0Eh N/A Write remote T
OSHT 0Fh N/A One-shot command (use send-byte format)
*If the device is in hardware standby mode at POR, both temperature registers read 0°C.
HIGH
LOW
HIGH
LOW
limit
limit
HIGH
LOW
limit
limit
HIGH
LOW
limit
limit
limit
limit
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The Alert Response can activate several different
slave devices simultaneously, similar to the SMBus
General Call. If more than one slave attempts to respond, bus arbitration rules apply, and the device with
the lower address code wins. The losing device does
not generate an acknowledge and continues to hold
the
ALERT line low until serviced (implies that the
host interrupt input is level-sensitive). Successful
reading of the alert response address clears the interrupt latch.
Command Byte Functions
The 8-bit command byte register (Table 4) is the master index that points to the various other registers
within the G767. The register’s POR state is 0000
0000, so that a Receive Byte transmission (a protocol
that lacks the command byte) that occurs immediately
after POR returns the current local temperature data.
The one-shot command immediately forces a new
conversion cycle to begin. In software standby mode
(RUN/STOP bit = high), a new conversion is begun,
after which the device returns to standby mode. If a
conversion is in progress when a one-shot command
is received in auto-convert mode (RUN/STOP bit = low)
between conversions, a new conversion begins, the
conversion rate timer is reset, and the next automatic
conversion takes place after a full delay elapses.
G767
Configuration Byte Functions
The configuration byte register (Table 5) is used to
mask (disable) interrupts and to put the device in
software standby mode. The lower six bits are internally set to (XX1111), making them “don’t care” bits.
Write zeros to these bits. This register’s contents can
be read back over the serial interface.
Status Byte Functions
The status byte register (Table 6) indicates which (if
any) temperature thresholds have been exceeded.
This byte also indicates whether or not the ADC is
converting and whether there is an open circuit in the
remote diode DXP-DXN path. After POR, the normal
state of all the flag bits is zero, assuming none of the
alarm conditions are present. The status byte is
cleared by any successful read of the status, unless
the fault persists. Note that the
latch is not automatically cleared when the status flag
bit is cleared.
When reading the status byte, you must check for internal bus collisions caused by asynchronous ADC
timing, or else disable the ADC prior to reading the
status byte (via the RUN/STOP bit in the configuration
byte). In one-shot mode, read the status byte only after the conversion is complete, which is 150ms max
after the one-shot conversion is commanded.
ALERT interrupt
Table 5. Configuration-Byte Bit Assignments
BIT NAME POR STATE FUNCTION
7 (MSB) MASK 0
6
5-0 RFU 0 Reserved for future use
Table 6. Status-Byte Bit Assignments
BIT NAME FUNCTION
7 (MSB) BUSY A high indicates that the ADC is busy converting.
6 LHIGH* A high indicates that the local high-temperature alarm has activated.
5 LLOW * A high indicates that the local low-temperature alarm has activated.
4 RHIGH* A high indicates that the remote high-temperature alarm has activated.
3 RLOW* A high indicates that the remote low-temperature alarm has activated.
2 OPEN* A high indicates a remote-diode continuity (open-circuit) fault.
1 RFU Reserved for future use (returns 0)
0 (LSB) RFU Reserved for future use (returns 0)
*These flags stay high until cleared by POR, or until the status byte register is read.
RUN /
STOP
0
Masks all
Standby mode control bit. If high, the device immediately stops converting and enters standby mode. If low, the device converts in either one-shot or timer mode.
ALERT
interrupts when high.
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G767
Table 7. Conversion-Rate Control Byte
DATA CONVERSION RATE (Hz) AVERAGE SUPPLY CURRENT (µA TYP, at Vcc = 3.3V)
00h 0.0625 30
01h 0.125 33
02h 0.25 35
03h 0.5 48
04h 1 70
05h 2 128
06h 4 225
07h 8 425
08h to FFh RFU -
Table 8. RLTS and RRTE Temp Register Update Timing Chart
OPERATING MODE
Auto-Convert Power-on reset N/A (0.25Hz) 156ms max
Auto-Convert
Auto-Convert
Auto-Convert Rate timer 0.0625Hz 20sec
Auto-Convert Rate timer 0.125Hz 10sec
Auto-Convert Rate timer 0.25Hz 5sec
Auto-Convert Rate timer 0.5Hz 2.5sec
Auto-Convert Rate timer 1Hz 1.25sec
Auto-Convert Rate timer 2Hz 625ms
Auto-Convert Rate timer 4Hz 312.5ms
Auto-Convert Rate timer 8Hz 237.5ms
Hardware Standby
Software Standby RUN/STOP bit N/A 156ms
Software Standby 1-shot command N/A 156ms
1-shot command, while idling between automatic conversions
1-shot command that occurs during a conversion
STBY
CONVERSION
INITIATED BY:
pin
NEW CONVERSION RATE
(CHANGED VIA WRITE TO WCRW)
N/A 156ms max
N/A
N/A 156ms
TIME UNTIL RLTS AND
RRTE ARE UPDATED
When current conversion is
complete (1-shot is ignored)
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 LHIGH, LLOW, RHIGH, and RLOW are
refreshed on the SMBus clock edge immediately following the stop condition, so there is no danger of losing temperature-related status data as a result of an
internal bus collision. The OPEN status bit (diode continuity fault) is only refreshed at the beginning of a
conversion, 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
Ver 2.2
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indicate reversals in long-term temperature changes
and instead use a current 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 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.
Valid A/D conversion results for both channels are
available one total conversion time (125ms nominal,
156ms maximum) after initiating a conversion, whether
conversion is initiated via the RUN/STOP bit, hard-
ware
STBY pin, one-shot command, or initial power-up.
Changing the conversion rate can also affect the delay
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until new results are available. See Table 8.
Slave Addresses
The G767 appears to the SMBus as one device having a common address for both ADC channels. The
device address can be set to one of nine different values by pin-strapping ADD0 and ADD1 so that more
than one G767 can reside on the same bus without
address conflicts (Table 9).
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 G767 also responds to the SMBus Alert Response slave address (see the Alert Response Address section).
POR AND UVLO
The G767 has a volatile memory. To prevent ambiguous
power-supply conditions from corrupting the data in
memory and causing erratic behavior, a POR voltage
detector monitors Vcc and clears the memory if Vcc falls
below 1.7V (typical, see Electrical Characteristics table).
When power is first applied and Vcc rises above 1.75V
(typical), the logic blocks begin operating, although reads
and writes at V
A second Vcc comparator, the ADC UVLO comparator,
prevents the ADC from converting until there is sufficient
headroom (Vcc = 2.8V typical).
levels below 3V are not recommended.
CC
G767
Table 9.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.
ADC begins auto-converting at a 0.25Hz rate.
Command byte is set to 00h to facilitate quick re-
mote Receive Byte queries.
T
and T
HIGH
limits, respectively.
registers are set to max and min
LOW
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G767
AB C
t
LOW
t
HIGH
DE
F
G
HIJ KLM
SMBCLK
SMBDATA
t
SU:STAtHD:STA
t
SU:DAT
t
HD:DAT
Figure 4. SMBus Write Timing Diagram
A = start condition H = LSB of data clocked into slave
B = MSB of address clocked into slave I = slave pulls SMBDATA line low
C = LSB of address clocked into slave J = acknowledge clocked into master
D = R/W bit clocked into slave K = acknowledge clocked pulse
E = slave pulls SMBDATA line low L = stop condition data executed by slave
F = acknowledge bit clocked into master M = new start condition
G = MSB of data clocked into slave
AB
AB
t
t
LOW
LOW
t
t
HIGH
HIGH
CDEF
CDEF
G
G
HI
HI
t
t
BUF
SU:STO
JK
JK
SMBCLK
SMBCLK
SMBDATA
SMBDATA
t
t
SU:STAtHD:STA
SU:STAtHD:STA
t
t
SU:DAT
SU:DAT
Figure 5. SMBus Read Timing Diagram
A = start condition
B = MSB of address clocked into slave
C = LSB of address clocked into slave
D = R/
W bit clocked into slave
E = slave pulls SMBDATA line low K= new start condition
F =acknowledge bit clocked into master
G = MSB of data clocked into master
H = LSB of data clocked into master
I = acknowledge clocked pulse
J = stop condition
t
t
t
t
SU:STO
SU:STO
BUF
BUF
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Package Information
7
°
(4X)
G767
C
E1
E
L
D
θ
A2 A
y
b
e
A1
Note:
1. Package body sizes exclude mold flash and gate burrs
2. Dimension L is measured in gage plane
3. Tolerance 0.10mm unless otherwise specified
4.
Controlling dimension is millimeter converted inch dimensions are not necessarily exact.
SYMBOL
A 1.35 1.60 1.75 0.053 0.064 0.069
A1 0.10 ----- 0.25 0.004 ----- 0.010
A2 ----- 1.45 ----- ----- 0.057 -----
b 0.20 0.25 0.30 0.008 0.010 0.012
C 0.19 ----- 0.25 0.007 ----- 0.010
D 4.80 ----- 5.00 0.189 ----- 0.197
E 5.80 ----- 6.20 0.228 ----- 0.244
E1 3.80 ----- 4.00 0.150 ----- 0.157
e ----- 0.64 ----- ----- 0.025 -----
L 0.40 ----- 1.27 0.016 ----- 0.050
y ----- ----- 0.10 ----- ----- 0.004
θ
MIN. NOM. MAX. MIN. NOM. MAX.
0º ----- 8º 0º ----- 8º
DIMENSION IN MM DIMENSION IN INCH
Taping Specification
Feed Direction
Feed Direction
Typical SSOP Package Orientation
Typical SSOP Package Orientation
GMT Inc. d oes not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and GMT Inc. reserves the right at any time without notice to change said circuitry and specifications.
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