GMT G767F Remote/local temperature sensor with smbus serial interface Datasheet

G767
Global Mixed-mode Technology Inc.
Remote/Local Temperature Sensor with SMBus
Serial Interface
Features
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General Description
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
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 (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 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.
Applications
Desktop and Notebook
Computers
Smart Battery Packs
LAN Servers
Industrial Controls
Central Office
Telecom Equipment
Test and Measurement
Multi-Chip Modules
Ordering Information
ORDER ORDER NUMBER
NUMBER
(Pb free)
G767
Pin Configuration
G767f
TEMP.
RANGE
PACKAGE
-55°C to +125°C
SSOP-16
Typical Operating Circuit
G767
3V TO 5.5V
N.C.
1
16
N.C
Vcc
2
15
STBY
DXP
3
14
SMBCLK
DXN
4
13
N.C.
N.C.
5
12
SMBDATA
ADD1
6
11
ALERT
GND
7
10
ADD0
GND 8
9
0.1 µF
200Ω
Vcc
DXP
STBY
SMBCLK
SMBDATA
2N3904
2200pF
DXN
ALERT
10k EACH
CLOCK
DATA
INTERRUPT
TO µC
ADD0 ADD1 GND
N.C.
SSOP-16
Ver: 2.5
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G767
Global Mixed-mode Technology Inc.
Absolute Maximum Ratings
ESD Protection (SMBCLK, SMBDATA, ALERT ,
human body model).………………………..……..4000V
ESD Protection (other pins, human body model)..2000V
Continuous Power Dissipation (T A = +70°C)
SSOP(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
Reflow Temperature (soldering, 10sec)…………....260°C
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, ALERT , STBY to GND…………
……………………………………………...…-0.3V to +6V
SMBDATA, ALERT Current………….-1mA to +50mA
DXN Current……………………..………………….±1mA
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.
Electrical Characteristics
(Vcc = + 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
ADC and power supply
Temperature Resolution (Note 1) Monotonicity guaranteed
Initial Temperature Error,
TA = +60°C to +100°C
Local Diode (Note 2)
TA = 0°C to +85°C
Temperature Error, Remote Di- TR = +60°C to +100°C
ode (Notes 2 and 3)
TR = -55°C to +125°C
Temperature Error, Local Diode
Including long-term drift
(Notes 1 and 2)
8
-2
-3
-3
-5
-2.5
-3.5
3.0
2.6
--1.0
-----
----------------2.8
50
1.7
50
3
--2
3
3
5
2.5
3.5
5.5
2.95
--2.5
--10
---
4
---
---
35
70
---
120
180
94
125
156
ms
-25
---
25
%
High level
80
100
120
Low level
ADD0, ADD1; momentary upon power-on reset
8
---
10
160
12
---
TA = +60°C to +100°C
TA = 0°C to +85°C
Supply-Voltage Range
Undervoltage Lockout Threshold Vcc input, disables A/D conversion, rising edge
Undervoltage Lockout Hysteresis
Power-On Reset Threshold
Vcc , falling edge
POR Threshold Hysteresis
SMBus static
Logic inputs forced
Standby Supply Current
Hardware or software
to Vcc or GND
standby, SMBCLK at 10kHz
Auto-convert mode,average meas- 0.25 conv/sec
Average Operating Supply
ured over 4sec. Logic inputs forced
Current
2.0 conv/sec
to Vcc or GND
Conversion Time
From stop bit to conversion complete(both channels)
Conversion Rate Timing Error
Remote-Diode Source Current
Address Pin Bias Current
MIN TYP MAX UNITS
Auto-convert mode
DXP forced to 1.5V
Ver: 2.5
Dec 14, 2004
Bits
°C
°C
°C
V
V
mV
V
mV
µA
µA
µA
µA
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G767
Global Mixed-mode Technology Inc.
Electrical Characteristics (continued)
(Vcc = + 3.3V, TA = 0 to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
SMBus Interface
Logic Input High Voltage
STBY , SMBCLK, SMBDATA; Vcc = 3V to 5.5V
2.2
---
---
V
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 Output High Leakage Current
ALERT forced to 5.5V
---
---
1
µA
Logic Input Current
SMBus Input Capacitance
Logic inputs forced to Vcc or GND
SMBCLK, SMBDATA
-1
---
--5
1
---
µA
pF
SMBus Clock Frequency
SMBCLK Clock Low Time
(Note 4)
tLOW , 10% to 10% points
DC
4.7
-----
100
---
kHz
µs
SMBCLK Clock High Time
SMBus Start-Condition Setup Time
tHIGH , 90% to 90% points
4
4.7
-----
-----
µs
µs
500
4
-----
-----
ns
µs
4
---
---
µs
800
---
---
ns
0
---
---
µs
---
---
1
µs
SMBus Repeated Start-Condition Setup Time tSU : STA , 90% to 90% points
SMBus Start-Condition Hold Time
tHD: STA , 10% of SMBDATA to 90% of SMBCLK
SMBus Start-Condition Setup Time
SMBus Data Valid to SMBCLK Rising-Edge
Time
SMBus Data-Hold Time
SMBCLK Falling Edge to SMBus Data-Valid
Time
tSD: STO , 90% of SMBDATA to 10% of SMBDATA
tSU: DAT , 10% or 90% of SMBDATA to 10% of
SMBCLK
tHD : DAT (Note 5)
Master clocking in data
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)
Initial Temperature Error, Local
Diode (Note 2)
Temperature Error, Remote Diode
(Notds2 and 3)
Monotonicity guaranteed
TA = +60°C to +100°C
TA = -55°C to +125°C
TR = +60°C to +100°C
TR = -55°C to +125°C
Supply-Voltage Range
Conversion Time
Conversion Rate Timing Error
From stop bit to conversion complete (both channels)
Auto-convert mode
8
-2
-----
--2
Bits
-3
-3
-----
3
3
-5
3.0
-----
5
5.5
94
-25
125
---
156
25
2.2
---
---
2.4
---
-----
--0.8
V
---
---
mA
°C
°C
V
ms
%
SMBus Interface
Logic Input High Voltage
STBY, SMBCLK, SMBDATA
Vcc = 3V
V
Logic Input Low Voltage
Vcc = 5.5V
STBY, SMBCLK, SMBDATA; Vcc = 3V to 5.5V
Logic Output Low Sink Current
ALERT, SMBDATA forced to 0.4V
6
ALERT Output High Leakage Current
ALERT forced to 5.5V
---
---
1
µA
Logic Input Current
Logic inputs forced to Vcc or GND
-2
---
2
µA
Note1: Guaranteed but not 100% tested.
Note2: Quantization error is not included in specifications for temperature accuracy. For example, if the G767 device 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. TR is the junction temperature of the remote 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: Specifications from -55°C to +125°C are guaranteed by design, not production tested.
Ver: 2.5
Dec 14, 2004
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Pin Description
G767
PIN
NAME
FUNCTION
1,5,9,13,16
N.C.
2
Vcc
3
DXP
No Connection. Not internally connected. May be used for PC board trace routing
Supply Voltage Input , 3V to 5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ω series resistor is
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.
4
DXN
6
ADD1
7,8
10
GND
ADD0
11
12
14
15
ALERT
Combined Current Sink and A/D Negative Input.
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.
Ground
SMBus Slave Address Select pin
SMBus Alert (interrupt) Output, open drain
SMBDATA SMBus Serial-Data Input / Output , open drain
SMBCLK SMBus Serial-Clock Input
Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode.
STBY
Low = standby mode, high = operate mode.
Detailed Description
The G767 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.
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.
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.
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.
ADC and Multiplexer
The ADC is an averaging type that integrates over a
Ver: 2.5
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G767
Global Mixed-mode Technology Inc.
STBY ADD0 ADD1
VCC
ADDRESS
DECODER
MUX
DXP
2
+
DXN
+
REMOTE
+
ADC
CONTROL
LOGIC
LOCAL
7
SMBUS
SMBDATA
SMBCLK
READ WRITE
DIODE
FAULT
8
8
8
REMOTE TEMPERATURE
DATA REGISTER
LOCAL EMPERATURE
DATA REGISTER
8
COMMAND BYTE
(INDEX) REGISTER
8
HIGH-TEMPETATURE
THRESHOLD (REMOTEHIGH)
HIGH-TEMPETATURE
THRESHOLD (LOCALTHIGH)
8
STATUS BYTE
REGISTER
LOW-TEMPETATURE
THRESHOLD (REMOTELOW)
LOW-TEMPETATURE
THRESHOLD (LOCAL TLOW)
CONFIGURATION
BYTE REGISTER
8
DIGITAL COMPARATOR
(REMOTE)
DIGITAL COMPARATOR
(LOCAL)
ALERT
SELECTED VIA
SLAVE ADD = 0001 100
S
Q
R
CONVERSION RATE
REGISTER
ALERT RESPONSE
ADDRESS REGISTER
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.
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.
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.
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
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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 current at the ALERT output. For example, at an 8Hz rate
and with ALERT sinking 1mA, the typical power dissipation 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:
Do not route the DXP-DXN lines next to the deflection
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 +12VDC. Leakage currents from PC
board contamination must be dealt with carefully,
since a 20MΩ leakage path from DXP to ground
causes about +1°C error.
dT = 2.7mW x 150°C /W = 0.4°C
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.
Even with these contrived circumstances, it is difficult
to introduce significant self-heating errors.
Table 1. Remote-Sensor Transistor Manufacturers
MANUFACTURER
Philips
Motorola(USA)
National Semiconductor(USA)
G767
Route through as few vias and crossunders as
possible to minimize copper/solder thermocouple effects.
MODEL NUMBER
PMBS3904
MMBT3904
MMBT3904
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.
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.
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.
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.
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.
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 Checklist
„ 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).
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.
Ver: 2.5
Dec 14, 2004
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Activate hardware standby mode by forcing the
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.
GND
10 MILS
10 MILS
DXP
MINIMUM
10 MILS
G767
DXN
10 MILS
GND
Figure 2. Recommended DXP/DXN PC Traces
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.
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.
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.
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 STBY pin low or via 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.
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.
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
RUN/STOP bit being high.
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Write Byte Format
S
ADDRESS
WR
ACK
COMMAND
7 bits
ACK
DATA
8 bits
ACK
P
8 bits
1
Slave Address: equivalent to chip- select line of a 3-wire interface
Command Byte: selects which register you are writing to
Data byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sam
pling rate)
Read Byte Format
S
ADDRESS WR
ACK
COMMAND
7 bits
ACK
S
8bits
ADDRESS
RD
ACK
DATA
7bits
///
P
8 bits
Slave Address: equivalent to chip- select line
Command Byte: selects which register you are reading from
Slave Address: repeated due to change in data-flow direction
Data byte: reads from the register set by the command byte
Send Byte Format
S
ADDRESS
WR
ACK
COMMAND
7 bits
ACK
P
///
P
8 bits
Command Byte: sends command with no data , usually used for one-shot command
Receive Byte Format
S
ADDRESS
RD
ACK
DATA
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
S = Start condition Shaded = Slave transmission P = Stop condition
/// = Not acknowledged
Figure 3. SMBus Protocols
Alarm Threshold Registers
Four registers store alarm threshold data, with
high-temperature (THIGH) and low-temperature (TLOW)
registers for each A/D channel. If either measured
temperature equals or exceeds the corresponding
alarm threshold value, an ALERT interrupt is asserted.
Table 2. Data Format (Twos-Complement)
DIGITAL OUTPUT
ROUND
TEMP.
TEMP.
DATA BITS
(°C)
(°C)
SIGN
MSB
LSB
+130.00
+127.00
+126.50
+126.00
+25.25
+0.50
+0.25
+0.00
-0.25
-0.50
+127
+127
+127
+126
+25
+1
+0
+0
+0
+0
0
0
0
0
0
0
0
0
0
0
111
111
111
111
001
000
000
000
000
000
1111
1111
1111
1110
1001
0001
0000
0000
0000
0000
-0.75
-1.00
-25.00
-25.50
-54.75
-55.00
-65.00
-70.00
-1
-1
-25
-25
-55
-55
-65
-65
1
1
1
1
1
1
1
1
111
111
110
110
100
100
011
011
1111
1111
0111
0110
1001
1001
1111
1111
The power-on-reset (POR) state of both THIGH registers
is full scale (0111 1111, or +127°C). The POR state of
both TLOW registers is 1100 1001 or -55°C.
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 VCC – 1V (typical) due to the diode current
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.
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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 THIGH or TLOW alarms at their POR settings.
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
VCC, the ADC reads +127°C for both remote and local
channels, and the device alarms.
and TLOW comparisons and when the remote diode is
disconnected (for continuity fault detection). The interrupt does not halt automatic conversions; new temperature data continues to be available over the
SMBus interface after ALERT is asserted. The interrupt 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.
Table 3. Read Format for Alert Response Address
(0001 100)
BIT
NAME
FUNCTION
7(MSB)
6
5
4
3
2
1
0(LSB)
ADD7
ADD6
ADD5
ADD4
ADD3
ADD2
ADD1
1
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 ALERT interrupt signal,
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).
Provide the current G767
slave address that was
latched at POR (Table 8)
Logic 1
ALERT Interrupts
The ALERT interrupt output signal is latched and
can only be cleared by reading the Alert Response
address. Interrupts are generated in response to THIGH
Table 4. Command-Byte Bit Assignments
REGISTER
COMMAND
POR STATE
RLTS
RRTE
RSL
RCL
RCRA
RLHN
RLLI
RRHI
RRLS
WCA
WCRW
WLHO
WLLM
WRHA
WRLN
OSHT
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
0000 0000*
0000 0000*
N/A
0000 0000
0000 0010
0111 1111
1100 1001
0111 1111
1100 1001
N/A
N/A
N/A
N/A
N/A
N/A
N/A
FUNCTINON
Read local temperature: returns latest temperature
Read remote temperature: returns latest temperature
Read status byte (flags, busy signal)
Read configuration byte
Read conversion rate byte
Read local THIGH limit
Read local TLOW limit
Read remote THIGH limit
Read remote TLOW limit
Write configuration byte
Write conversion rate byte
Write local THIGH limit
Write local TLOW limit
Write remote THIGH limit
Write remote TLOW limit
One-shot command (use send-byte format)
*If the device is in hardware standby mode at POR, both temperature registers read 0°C.
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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.
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.
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 ALERT interrupt
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.
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.
Table 5. Configuration-Byte Bit Assignments
BIT
NAME
POR STATE
7 (MSB)
MASK
0
6
5-0
RUN /
STOP
RFU
0
0
FUNCTION
Masks all ALERT interrupts when high.
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.
Reserved for future use
Table 6. Status-Byte Bit Assignments
BIT
NAME
7 (MSB)
BUSY
FUNCTION
6
5
LHIGH*
LLOW*
A high indicates that the local high-temperature alarm has activated.
A high indicates that the local low-temperature alarm has activated.
4
3
2
1
0 (LSB)
RHIGH*
RLOW*
OPEN*
RFU
RFU
A high indicates that the remote high-temperature alarm has activated.
A high indicates that the remote low-temperature alarm has activated.
A high indicates a remote-diode continuity (open-circuit) fault.
Reserved for future use (returns 0)
Reserved for future use (returns 0)
A high indicates that the ADC is busy converting.
*These flags stay high until cleared by POR, or until the status byte register is read.
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Table 7. Conversion-Rate Control Byte
DATA
CONVERSION RATE (Hz)
AVERAGE SUPPLY CURRENT (µA TYP, at Vcc = 3.3V)
00h
01h
0.0625
0.125
30
33
02h
03h
0.25
0.5
35
48
04h
05h
06h
07h
08h to FFh
1
2
4
8
RFU
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 between automatic conversions
N/A
156ms max
Auto-Convert
1-shot command that occurs durN/A
ing a conversion
When current conversion is
complete (1-shot is ignored)
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
STBY pin
N/A
156ms
Software Standby
RUN/STOP bit
N/A
156ms
Software Standby
1-shot command
N/A
156ms
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.
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 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.
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-
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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, hardware STBY pin, one-shot command, or initial power-up.
Changing the conversion rate can also affect the delay
until new results are available. See Table 8.
Table 9.Slave Address Decoding (ADD0 and ADD1)
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).
ADD0
ADD1
ADDRESS
GND
GND
GND
High-Z
0011 000
0011 001
GND
High-Z
Vcc
GND
0011 010
0101 001
High-Z
High-Z
Vcc
Vcc
Vcc
High-Z
Vcc
GND
High-Z
Vcc
0101 010
0101 011
1001 100
1001 101
1001 110
Note: High-Z means that the pin is left unconnected
and floating.
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.
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 remote Receive Byte queries.
„ THIGH and TLOW registers are set to max and min
limits, respectively.
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 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).
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A
B
tLOW tHIGH
C
D
G
E F
H
I
J
K
M
L
SMBCLK
SMBDATA
tSU:STA tHD:STA
tHD:DAT
tSU:DAT
tSU:STO
tBUF
Figure 4. SMBus Write 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
F = acknowledge bit clocked into master
G = MSB of data clocked into slave
A
B
tLOW tHIGH
C
H = LSB of data clocked into slave
I = slave pulls SMBDATA line low
J = acknowledge clocked into master
K = acknowledge clocked pulse
L = stop condition data executed by slave
M = new start condition
D
E F
G
H
J
I
K
SMBCLK
SMBDATA
tSU:STA tHD:STA
tSU:STO
tSU:DAT
tBUF
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
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
K= new start condition
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Package Information
C
E1
E
L
D
θ
7°
(4X)
A2
e
y
A
A1
b
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.
MIN.
DIMENSION IN MM
NOM.
MAX.
MIN.
DIMENSION IN INCH
NOM.
MAX.
A
A1
1.35
0.10
1.60
-----
1.75
0.25
0.053
0.004
0.064
-----
0.069
0.010
A2
b
----0.20
1.45
0.25
----0.30
----0.008
0.057
0.010
----0.012
C
D
0.19
4.80
---------
0.25
5.00
0.007
0.189
---------
0.010
0.197
E
E1
5.80
3.80
---------
6.20
4.00
0.228
0.150
---------
0.244
0.157
e
L
y
θ
----0.40
----0º
0.64
-------------
----1.27
0.10
8º
----0.016
----0º
0.025
-------------
----0.050
0.004
8º
SYMBOL
Taping Specification
PACKAGE
Q’TY/REEL
SSOP-16
2,500 ea
F e e d D ir e c tio n
T y p ic a l S S O P P a c k a g e O r ie n ta tio n
GMT Inc. does 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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