TI LM82 Remote diode and local digital temperature sensor with two-wire interface Datasheet

LM82
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LM82 Remote Diode and Local Digital Temperature Sensor with Two-Wire Interface
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FEATURES
DESCRIPTION
•
The LM82 is a digital temperature sensor with a 2
wire serial interface that senses the voltage and thus
the temperature of a remote diode using a DeltaSigma analog-to-digital converter with a digital overtemperature detector. The LM82 accurately senses
its own temperature as well as the temperature of
external devices, such as Pentium II Processors or
diode connected 2N3904s. The temperature of any
ASIC can be detected using the LM82 as long as a
dedicated diode (semiconductor junction) is available
on the die. Using the SMBus interface a host can
access the LM82's registers at any time. Activation of
a T_CRIT_A output occurs when any temperature is
greater than a programmable comparator limit,
T_CRIT. Activation of an INT output occurs when any
temperature is greater than its corresponding
programmable comparator HIGH limit.
1
2
•
•
•
•
•
•
Accurately Senses Die Temperature of Remote
ICs, or Diode Junctions
On-board Local Temperature Sensing
SMBus and I2C Compatible Interface, Supports
SMBus 1.1 TIMEOUT
Two Interrupt Outputs: INT and T_CRIT_A
Register Readback Capability
7 bit Plus Sign Temperature Data Format, 1°C
Resolution
2 Address Select Pins Allow Connection of 9
LM82s on a Single Bus
APPLICATIONS
•
•
•
•
•
System Thermal Management
Computers
Electronic Test Equipment
Office Electronics
HVAC
KEY SPECIFICATIONS
•
•
•
•
Supply Voltage: 3.0 to 3.6V
Supply Current: 0.8mA (max)
Local Temp Accuracy (includes quantization
error):
– 0 to +85 ±3.0°C (max)
Remote Diode Temp Accuracy (includes
quantization error):
– +25°C to +100°C ±3°C (max)
– 0°C to +125°C ±4°C (max)
The host can program as well as read back the state
of the T_CRIT register and the 2 T_HIGH registers.
Three state logic inputs allow two pins (ADD0, ADD1)
to select up to 9 SMBus address locations for the
LM82. The sensor powers up with default thresholds
of 127°C for T_CRIT and all T_HIGHs. The LM82 is
pin for pin and register compatible with the LM84,
Maxim MAX1617 and Analog Devices ADM1021.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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Simplified Block Diagram
3.0V-3.6V
D+
D-
Temp
Sensor
Circuitry
T_CRIT_A
8-bit '6 A/D
Converter
INT
Control
Logic
Temperature
Registers
T_CRIT
Limit
Register
HIGH
Limit
Registers
Configuration and
Status Registers
ADD0
Mfr ID
Register
SMBData
Two-Wire Serial Interface
ADD1
SMBCLK
Connection Diagram
Figure 1. SSOP-TOP VIEW
See DBQ Package
2
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Typical Application
PIN DESCRIPTIONS
Label
Pin #
NC
1, 5
VCC
2
D+
3
D−
4
Function
Typical Connection
floating, unconnected
Left floating. PC board traces may be routed through the pads
for these pins. No restrictions applied.
Positive Supply Voltage Input
DC Voltage from 3.0 V to 3.6 V
Diode Current Source
To Diode Anode. Connected to remote discrete diode junction
or to the diode junction on a remote IC whose die temperature
is being sensed. When not used they should be left floating.
Diode Return Current Sink
To Diode Cathode. Must float when not used.
Ground (Low, “0”), VCC (High, “1”) or open (“TRI-LEVEL”)
ADD0–ADD1
10, 6
User-Set SMBus (I2C) Address
Inputs
GND
7, 8
Power Supply Ground
Ground
Manufacturing test pins.
Left floating. PC board traces may be routed through the pads
for these pins, although the components that drive these traces
should share the same supply as the LM82 so that the
Absolute Maximum Rating, Voltage at Any Pin, is not violated.
NC
9, 13, 15
INT
11
Interrupt Output, open-drain
Pull Up Resistor, Controller Interrupt or Alert Line
From and to Controller, Pull-Up Resistor
SMBData
12
SMBus (I2C) Serial BiDirectional Data Line, opendrain output
SMBCLK
14
SMBus (I2C) Clock Input
From Controller, Pull-Up Resistor
16
Critical Temperature Alarm,
open-drain output
Pull Up Resistor, Controller Interrupt Line or System Shutdown
T_CRIT_A
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
(1)
Absolute Maximum Ratings
−0.3 V to 6.0 V
Supply Voltage
Voltage at SMBData,
SMBCLK, T_CRIT_A & INT pins
−0.5V to 6V
−0.3 V to (VCC + 0.3 V)
Voltage at Other Pins
D− Input Current
±1 mA
Input Current at All Other Pins
Package Input Current
(2)
5 mA
(2)
20 mA
SMBData, T_CRIT_A, INT Output Sink Current
10 mA
−65°C to +150°C
Storage Temperature
Soldering Information, Lead Temperature
SSOP Package
(3)
Vapor Phase (60 seconds)
215°C
Infrared (15 seconds)
ESD Susceptibility
(4)
220°C
Human Body Model
2000 V
Machine Model
(1)
(2)
(3)
(4)
250 V
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not
apply when operating the device beyond its rated operating conditions.
When the input voltage (VI) at any pin exceeds the power supplies (VI < GND or VI > VCC), the current at that pin should be limited to 5
mA. The 20 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input
current of 5 mA to four. Parasitic components and or ESD protection circuitry are shown in the figure below for the LM82's pins. The
nominal breakdown voltage of the zener D3 is 6.5 V. Care should be taken not to forward bias the parasitic diode, D1, present on pins:
D+, D−, ADD1 and ADD0. Doing so by more than 50 mV may corrupt a temperature or voltage measurement.
See the section titled “Surface Mount” found in a current Texas Instruments Linear Data Book for other methods of soldering surface
mount devices.
Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin.
Operating Ratings
Specified Temperature Range
TMIN to TMAX
−40°C to +125°C
LM82
Supply Voltage Range (VCC)
+3.0V to +3.6V
Temperature-to-Digital Converter Characteristics
Unless otherwise noted, these specifications apply for VCC=+3.0 Vdc to 3.6 Vdc. Boldface limits apply for TA = TJ = TMIN to
TMAX; all other limits TA= TJ=+25°C, unless otherwise noted.
Parameter
Temperature Error using Local Diode
Typical (1)
Limits (2)
Units
(Limit)
±1
±3
°C (max)
TA = −40 °C to +125°C,
VCC=+3.3V
±4
°C (max)
TA = +60 °C to +100°C,
VCC=+3.3V
±3
TA = 0 °C to +100°C,
VCC=+3.3V
±3
°C (max)
TA = 0 °C to +125°C,
VCC=+3.3V
±4
°C (max)
Conditions
(3)
Temperature Error using Remote Diode
TA = 0 °C to +85°C,
VCC=+3.3V
(3)
Resolution
(1)
(2)
(3)
4
°C (max)
8
Bits
1
°C
Typicals are at TA = 25°C and represent most likely parametric norm.
Limits are ensured to AOQL (Average Outgoing Quality Level).
The Temperature Error will vary less than ±1.0°C for a variation in VCC of 3V to 3.6V from the nominal of 3.3V.
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Temperature-to-Digital Converter Characteristics (continued)
Unless otherwise noted, these specifications apply for VCC=+3.0 Vdc to 3.6 Vdc. Boldface limits apply for TA = TJ = TMIN to
TMAX; all other limits TA= TJ=+25°C, unless otherwise noted.
Parameter
Conditions
Conversion Time of All Temperatures
Quiescent Current
(5)
Typical (1)
(4)
SMBus (I2C) Inactive
Limits (2)
460
600
ms (max)
0.500
0.80
mA (max)
125
μA (max)
D− Source Voltage
0.7
V
(D+ − D−)=+ 0.65V; high level
Diode Source Current
Low level
60
μA (min)
15
μA (max)
5
μA (min)
T_CRIT_A and INT Output Saturation
Voltage
IOUT = 3.0 mA
0.4
Power-On Reset Threshold
On VCC input, falling edge
2.3
1.8
Local and Remote T_CRIT and HIGH
Default Temperature settings
(4)
Units
(Limit)
See
(6)
V (max)
V (max)
V (min)
+127
°C
This specification is provided only to indicate how often temperature data is updated. The LM82 can be read at any time without regard
to conversion state (and will yield last conversion result).
Quiescent current will not increase substantially with an active SMBus.
Default values set at power up.
(5)
(6)
Logic Electrical CharacteristicsDIGITAL DC CHARACTERISTICS
Unless otherwise noted, these specifications apply for VCC=+3.0 to 3.6 Vdc. Boldface limits apply for TA = TJ = TMIN to
TMAX; all other limits TA= TJ=+25°C, unless otherwise noted.
Symbol
Parameter
Conditions
Typical (1)
Limits (2)
Units
(Limit)
SMBData, SMBCLK
VIN(1)
Logical “1” Input Voltage
2.1
V (min)
VIN(0)
Logical “0”Input Voltage
0.8
V (max)
VIN(HYST)
SMBData and SMBCLK Digital Input
Hysteresis
300
mV
IIN(1)
Logical “1” Input Current
VIN = VCC
0.005
1.5
μA (max)
IIN(0)
Logical “0” Input Current
VIN = 0 V
−0.005
1.5
μA (max)
ADD0, ADD1
VIN(1)
Logical “1” Input Voltage
VCC
1.5
V (min)
VIN(0)
Logical “0”Input Voltage
GND
0.6
V (max)
IIN(1)
Logical “1” Input Current
VIN = VCC
2
μA (max)
IIN(0)
Logical “0” Input Current
VIN = 0 V
-2
μA (max)
ALL DIGITAL INPUTS
CIN
Input Capacitance
20
pF
ALL DIGITAL OUTPUTS
IOH
High Level Output Current
VOH = VCC
100
μA (max)
VOL
SMBus Low Level Output Voltage
IOL = 3 mA
IOL = 6 mA
0.4
0.6
V (max)
(1)
(2)
Typicals are at TA = 25°C and represent most likely parametric norm.
Limits are ensured to AOQL (Average Outgoing Quality Level).
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Logic Electrical CharacteristicsSMBus DIGITAL SWITCHING CHARACTERISTICS
Unless otherwise noted, these specifications apply for VCC=+3.0 Vdc to +3.6 Vdc, CL (load capacitance) on output lines =
80 pF. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25°C, unless otherwise noted.
The switching characteristics of the LM82 fully meet or exceed the published specifications of the SMBus or I2C bus. The
following parameters are the timing relationships between SMBCLK and SMBData signals related to the LM82. They are not
the I2C or SMBus bus specifications.
Symbol
Parameter
fSMB
SMBus Clock Frequency
tLOW
SMBus Clock Low Time
Typical (1)
Limits (2)
Units
(Limit)
100
10
kHz (max)
kHz (min)
10 % to 10 %
1.3
25
μs (min)
ms (max)
10
ms (max)
0.6
Conditions
tLOWMEXT Cumulative Clock Low Extend Time
tHIGH
SMBus Clock High Time
90 % to 90%
tR,SMB
SMBus Rise Time
10% to 90%
1
tF,SMB
SMBus Fall Time
90% to 10%
0.3
tOF
Output Fall Time
CL = 400 pF,
IO = 3 mA
tTIMEOUT
SMBData and SMBCLK Time Low for Reset of
Serial Interface (3)
t1
t2, tSU;DAT
μs (min)
μs (max)
ns (max)
250
ns (max)
25
40
ms (min)
ms (max)
SMBCLK (Clock) Period
10
μs (min)
Data In Setup Time to SMBCLK High
100
ns (min)
t3, tHD;DAT
Data Out Stable after SMBCLK Low
300
TBD
ns (min)
ns (max)
t4, tHD;STA
SMBData Low Setup Time to SMBCLK Low
100
ns (min)
t5, tSU;STO
SMBData High Delay Time after SMBCLK High
(Stop Condition Setup)
100
ns (min)
t6, tSU;STA
SMBus Start-Condition Setup Time
0.6
μs (min)
tBUF
SMBus Free Time
1.3
μs (min)
(1)
(2)
(3)
Typicals are at TA = 25°C and represent most likely parametric norm.
Limits are ensured to AOQL (Average Outgoing Quality Level).
Holding the SMBData and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will cause the LM82 to reset SMBData and
SMBCLK to the IDLE state of an SMBus communication (SMBCLK and SMBData set High).
Figure 2. SMBus Communication
6
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Figure 3. SMBus TIMEOUT
Pin Name
D1
D2
D3
D4
NC (pins 1 & 5)
D1
T_CRIT_A & INT
x (1)
VCC
D+
x
x
x
D−
x
x
x
ADD0, ADD1
x
x
x
(1)
Pin Name
D3
x
x
x
x
SMBCLK
x
x
NC (pin 13)
x
x
NC (pins 9 & 15)
D4
x
SMBData
x
D2
x
Note: An x indicates that the diode exists.
Figure 4. ESD Protection Input Structure
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Figure 5. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)
Figure 6. Printed Circuit Board Used for Thermal Resistance Specifications
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FUNCTIONAL DESCRIPTION
The LM82 temperature sensor incorporates a band-gap type temperature sensor using a Local or Remote diode
and an 8-bit ADC (Delta-Sigma Analog-to-Digital Converter). The LM82 is compatible with the serial SMBus and
I2C two wire interfaces. Digital comparators compare Local (LT) and Remote (RT) temperature readings to userprogrammable setpoints (LHS, RHS, and TCS). Activation of the INT output indicates that a comparison is
greater than the limit preset in a HIGH register. The T_CRIT setpoint (TCS) interacts with all the temperature
readings. Activation of the T_CRIT_A output indicates that any or all of the temperature readings have exceed
the T_CRIT setpoint.
CONVERSION SEQUENCE
The LM82 converts its own temperature as well as a remote diode temperature in the following sequence:
1. Local Temperature (LT)
2. Remote Diode (RT)
This round robin sequence takes approximately 480 ms to complete.
INT OUTPUT and T_HIGH LIMITS
Each temperature reading (LT, and RT) is associated with a T_HIGH setpoint register (LHS, RHS). At the end of
a temperature reading a digital comparison determines whether that reading has exceeded its HIGH setpoint. If
the temperature reading is greater than the HIGH setpoint, a bit is set in one of the Status Registers, to indicate
which temperature reading, and the INT output is activated.
Local and remote temperature diodes are sampled in sequence by the A/D converter. The INT output and the
Status Register flags are updated at the completion of a conversion, which occurs approximately 60 ms after a
temperature diode is sampled. INT is deactivated when the Status Register, containing the set bit, is read and a
temperature reading is less than or equal to it's corresponding HIGH setpoint, as shown in Figure 7. Figure 8
shows a simplified logic diagram for the INT output and related circuitry.
* Note: Status Register Bits are reset by a read of Status Register where bit is located.
Figure 7. INT Temperature Response Diagram
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Figure 8. INT output related circuitry logic diagram
The INT output can be disabled by setting the INT mask bit, D7, of the configuration register. INT can be
programmed to be active high or low by the state of the INT inversion bit, D1, in the configuration register. A “0”
would program INT to be active low. INT is an open-drain output.
T_CRIT_A OUTPUT and T_CRIT LIMIT
T_CRIT_A is activated when any temperature reading is greater than the limit preset in the critical temperature
setpoint register (T_CRIT), as shown in Figure 9. The Status Registers can be read to determine which event
caused the alarm. A bit in the Status Registers is set high to indicate which temperature reading exceeded the
T_CRIT setpoint temperature and caused the alarm, see STATUS REGISTER.
Local and remote temperature diodes are sampled in sequence by the A/D converter. The T_CRIT_A output and
the Status Register flags are updated at the completion of a conversion. T_CRIT_A and the Status Register flags
are reset only after the Status Register is read and if a temperature conversion is below the T_CRIT setpoint, as
shown in Figure 9. Figure 10 shows a simplified logic diagram of the T_CRIT_A and related circuitry.
* Note: Status Register Bits are reset by a read of Status Register where bit is located.
Figure 9. T_CRIT_A Temperature Response Diagram
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Figure 10. T_CRIT_A output related circuitry logic diagram
Located in the Configuration Register are the mask bits for each temperature reading, see CONFIGURATION
REGISTER . When a mask bit is set, its corresponding status flag will not propagate to the T_CRIT_A output, but
will still be set in the Status Registers. Configuration register bits D5 and D3, labled “Remote T_CRIT_A mask”
must be set high before the T_CRIT setpoint is lowered in order for the T_CRIT_A output to function properly.
Setting all four mask bits or programming the T_CRIT setpoint to 127°C will disable the T_CRIT_A output.
POWER ON RESET DEFAULT STATES
LM82 always powers up to these known default states:
1. Command Register set to 00h
2. Local Temperature set to 0°C
3. Remote Temperature set to 0°C until the LM82 senses a diode present between the D+ and D− input pins.
4. Status Register set to 00h.
5. Configuration Register set to 00h; INT enabled and all T_CRIT setpoints enabled to activate T_CRIT_A.
6. Local and Remote T_CRIT set to 127°C
SMBus INTERFACE
The LM82 operates as a slave on the SMBus, so the SMBCLK line is an input (no clock is generated by the
LM82) and the SMBData line is bi-directional. According to SMBus specifications, the LM82 has a 7-bit slave
address. Bit 4 (A3) of the slave address is hard wired inside the LM82 to a 1. The remainder of the address bits
are controlled by the state of the address select pins ADD1 and ADD0, and are set by connecting these pins to
ground for a low, (0), to VCC for a high, (1), or left floating (TRI-LEVEL).
Therefore, the complete slave address is:
A6
A5
A4
1
A2
A1
MSB
A0
LSB
and is selected as follows:
Address Select Pin State
ADD0
LM82 SMBus Slave Address
ADD1
A6:A0 binary
0
0
001 1000
0
TRI-LEVEL
001 1001
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Address Select Pin State
LM82 SMBus Slave Address
ADD0
ADD1
A6:A0 binary
0
1
001 1010
TRI-LEVEL
0
010 1001
TRI-LEVEL
TRI-LEVEL
010 1010
TRI-LEVEL
1
010 1011
1
0
100 1100
1
TRI-LEVEL
100 1101
1
1
100 1110
The LM82 latches the state of the address select pins during the first read or write on the SMBus. Changing the
state of the address select pins after the first read or write to any device on the SMBus will not change the slave
address of the LM82.
TEMPERATURE DATA FORMAT
Temperature data can be read from the Local and Remote Temperature, T_CRIT, and HIGH setpoint registers;
and written to the T_CRIT and HIGH setpoint registers. Temperature data is represented by an 8-bit, two's
complement byte with an LSB (Least Significant Bit) equal to 1°C:
Temperature
Digital Output
Binary
Hex
+125°C
0111 1101
7Dh
+25°C
0001 1001
19h
+1°C
0000 0001
01h
0°C
0000 0000
00h
FFh
−1°C
1111 1111
−25°C
1110 0111
E7h
−55°C
1100 1001
C9h
OPEN-DRAIN OUTPUTS
The SMBData, INT and T_CRIT_A outputs are open-drain outputs and do not have internal pull-ups. A “high”
level will not be observed on these pins until pull-up current is provided from some external source, typically a
pull-up resistor. Choice of resistor value depends on many system factors but, in general, the pull-up resistor
should be as large as possible. This will minimize any internal temperature reading errors due to internal heating
of the LM82. The maximum resistance of the pull up, based on LM82 specification for High Level Output Current,
to provide a 2.1V high level, is 30kΩ. Care should be taken in a noisy system because a high impedance pull-up
will be more likely to couple noise into the signal line.
DIODE FAULT DETECTION
Before each external conversion the LM82 goes through an external diode fault detection sequence. If D+ input
is shorted to VCC or floating then the temperature reading will be +127 °C, and the OPEN bit in the Status
Register will be set. If the T_CRIT setpoint is set to less than +127 °C then the D+ input RTCRIT bit in the Status
Register will be set which will activate the T_CRIT_A output, if enabled. If a D+ is shorted to GND or D−, its
temperature reading will be 0 °C and its OPEN bit in the Status Register will not be set.
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COMMUNICATING with the LM82
There are 13 data registers in the LM82, selected by the Command Register. At power-up the Command
Register is set to “00”, the location for the Read Local Temperature Register. The Command Register latches the
last location it was set to. Reading the Status Register resets T_CRIT_A and INT, so long as a temperature
comparison does not signal a fault (see INT OUTPUT and T_HIGH LIMITS and T_CRIT_A OUTPUT and
T_CRIT LIMIT). All other registers are predefined as read only or write only. Read and write registers with the
same function contain mirrored data.
A Write to the LM82 will always include the address byte and the command byte. A write to any register requires
one data byte.
Reading the LM82 can take place either of two ways:
1. If the location latched in the Command Register is correct (most of the time it is expected that the Command
Register will point to one of the Read Temperature Registers because that will be the data most frequently
read from the LM82), then the read can simply consist of an address byte, followed by retrieving the data
byte.
2. If the Command Register needs to be set, then an address byte, command byte, repeat start, and another
address byte will accomplish a read.
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The data byte has the most significant bit first. At the end of a read, the LM82 can accept either Acknowledge or
No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master has
read its last byte).
SERIAL INTERFACE ERROR RECOVERY
The LM82 SMBus lines will be reset to the SMBus idle state if the SMBData or SMBCLK lines are held low for 40
ms or more (tTIMEOUT). The LM82 may or may not reset the state of the serial interface logic if either of the
SMBData or SMBCLK lines are held low between 25 ms and 40 ms. TIMEOUT allows a clean recovery in cases
where the master may be reset while the LM82 is transmitting a low bit thus preventing possible bus lock up.
Whenever the LM82 sees the start condition its serial interface will reset to the beginning of the communication,
thus the LM82 will expect to see an address byte next. This simplifies recovery when the master is reset while
the LM82 is transmitting a high.
LM82 Registers
COMMAND REGISTER
Selects which registers will be read from or written to. Data for this register should be transmitted during the
Command Byte of the SMBus write communication.
P7
P6
P5
P4
0
P3
P2
P1
P0
Command Select
P0-P7: Command Select
Command Select
Address
Power On Default State
Register Name
<P7:P0> hex
<D7:D0> binary
<D7:D0> decimal
00h
0000 0000
0
RLT
Read Local Temperature
01h
0000 0000
0
RRT
Read Remote Temperature
02h
0000 0000
0
RSR
Read Status Register
03h
0000 0000
0
RC
Read Configuration
04h
0000 0000
0
05h
0111 1111
127
RLHS
0111 1111
127
RRHS
Reserved
06h
Read Local HIGH Setpoint
Reserved
07h
08h
Read Remote HIGH Setpoint
Reserved
09h
0000 0000
WC
0Ah
Write Configuration
Reserved
0Bh
0111 1111
127
WLHS
0111 1111
127
WRHS
0Ch
Write Local HIGH Setpoint
Reserved
0Dh
0Eh-2Fh
30h-31h
35h
0000 0000
0
0000 0000
0
0111 1111
127
0111 1111
127
0111 1111
127
Reserved
Reserved for Future Use
Reserved
36h-37h
38h
Write Remote HIGH Setpoint
Reserved for Future Use
32h-34h
Reserved for Future Use
Reserved
39h
Reserved for Future Use
3Ah
Reserved
3Bh-41h
42h
Reserved for Future Use
RTCS
43h-4Fh
14
Register Function
Read T_CRIT Setpoint
Reserved for Future Use
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Command Select
Address
Power On Default State
Register Name
<P7:P0> hex
<D7:D0> binary
<D7:D0> decimal
50h
0111 1111
127
0111 1111
127
0111 1111
127
Register Function
Reserved
51h
Reserved for Future Use
52h
Reserved
53h-59h
Reserved for Future Use
5Ah
WTCS
Write T_CRIT Setpoint
5Ch-6Fh and F0hFDh
Reserved for Future Use
FEh
0000 0001
1
RMID
Read Manufacturers ID
FFh
0000 0011
3
RSR
Read Stepping or Die Revision Code
LOCAL and REMOTE TEMPERATURE REGISTERS (LT, and RT)
Table 1. LOCAL and REMOTE TEMPERATURE REGISTERS (LT, and RT) (Read Only Address 00h, and
01h):
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
D7–D0: Temperature Data. One LSB = 1°C. Two's complement format.
STATUS REGISTER
Table 2. STATUS REGISTER (Read Only Address 02h):
D7
D6
D5
D4
D3
D2
D1
D0
0
LHIGH
0
RHIGH
0
OPEN
RCRIT
LCRIT
Power up default is with all bits “0” (zero).
D0: LCRIT: When set to a 1 indicates an Local Critical Temperature alarm.
D1: RCRIT: When set to a 1 indicates a Remote Diode Critical Temperature alarm.
D2: D2OPEN: When set to 1 indicates a Remote Diode disconnect.
D4: D2RHIGH: When set to 1 indicates a Remote Diode HIGH Temperature alarm.
D6: LHIGH: When set to 1 indicates a Local HIGH Temperature alarm.
D7, D5, and D3: These bits are always set to 0 and reserved for future use.
MANUFACTURERS ID AND DIE REVISION (Stepping) REGISTERS
MANUFACTURERS ID AND DIE REVISION (Stepping) REGISTERS (Read Address FEh and FFh) Default
value 01h for Manufacturers ID(FEh ).
CONFIGURATION REGISTER
Table 3. CONFIGURATION REGISTER (Read Address 03h/Write Address 09h):
D7
D6
D5
D4
D3
D2
D1
D0
INT mask
0
Remote
T_CRIT_A
mask
Remote
T_CRIT_A
mask
Remote
T_CRIT_A
mask
Local
T_CRIT_A
mask
INT Inversion
0
Power up default is with all bits “0” (zero).
D7: INT mask: When set to 1 INT interrupts are masked.
D5: T_CRIT mask, this bit must be set to a 1 before the T_CRIT setpoint is lowered below 127 in order for
T_CRIT_A pin to function properly.
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D4: T_CRIT mask for Remote temperature, when set to 1 a remote temperature reading that exceeds T_CRIT
setpoint will not activate the T_CRIT_A pin.
D3: T_CRIT mask, this bit must be set to a 1 before the T_CRIT setpoint is lowered below 127 in order for
T_CRIT_A pin to function properly.
D2: T_CRIT mask for Local reading, when set to 1 a Local temperature reading that exceeds T_CRIT setpoint
will not activate the T_CRIT_A pin.
D1: INT active state inversion. When INT Inversion is set to a 1 the active state of the INT output will be a logical
high. A low would then select an active state of a logical low.
D6 and D0: These bits are always set to 0 and reserved for future use. A write of 1 will return a 0 when read.
LOCAL AND REMOTE HIGH SETPOINT REGISTERS (LHS, RHS)
Table 4. LOCAL AND REMOTE HIGH SETPOINT REGISTERS (LHS, RHS) (Read Address 05h, 07h/Write
Address 0Bh, 0Dh):
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
D7–D0: HIGH setpoint temperature data. Power up default is LHIGH = RHIGH=127°C.
T_CRIT REGISTER (TCS)
Table 5. T_CRIT REGISTER (TCS) (Read Address 42h/Write Address 5Ah):
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
D7–D0: T_CRIT setpoint temperature data. Power up default is T_CRIT = 127°C.
16
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SMBus Timing Diagrams
Figure 11. (a) Serial Bus Write to the internal Command Register followed by a the Data Byte
Figure 12. (b) Serial Bus Write to the internal Command Register
Figure 13. (c) Serial Bus Read from a Register with the internal Command Register preset to desired
value
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Application Hints
The LM82 can be applied easily in the same way as other integrated-circuit temperature sensors and its remote
diode sensing capability allows it to be used in new ways as well. It can be soldered to a printed circuit board,
and because the path of best thermal conductivity is between the die and the pins, its temperature will effectively
be that of the printed circuit board lands and traces soldered to the LM82's pins. This presumes that the ambient
air temperature is almost the same as the surface temperature of the printed circuit board; if the air temperature
is much higher or lower than the surface temperature, the actual temperature of the of the LM82 die will be at an
intermediate temperature between the surface and air temperatures. Again, the primary thermal conduction path
is through the leads, so the circuit board temperature will contribute to the die temperature much more strongly
than will the air temperature.
To measure temperature external to the LM82's die, use a remote diode. This diode can be located on the die of
a target IC, allowing measurement of the IC's temperature, independent of the LM82's temperature. The LM82
has been optimized to measure the remote diode of a Pentium II processor as shown in Figure 14. A discrete
diode can also be used to sense the temperature of external objects or ambient air. Remember that a discrete
diode's temperature will be affected, and often dominated, by the temperature of its leads.
Figure 14. Pentium or 3904 Temperature vs LM82 Temperature Reading
Most silicon diodes do not lend themselves well to this application. It is recommended that a 2N3904 transistor
base emitter junction be used with the collector tied to the base.
A diode connected 2N3904 approximates the junction available on a Pentium microprocessor for temperature
measurement. Therefore, the LM82 can sense the temperature of this diode effectively.
ACCURACY EFFECTS OF DIODE NON-IDEALITY FACTOR
The technique used in today's remote temperature sensors is to measure the change in VBE at two different
operating points of a diode. For a bias current ratio of N:1, this difference is given as:
where
•
18
η is the non-ideality factor of the process the diode is manufactured on,
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•
•
•
•
q is the electron charge,
k is the Boltzmann's constant,
N is the current ratio,
T is the absolute temperature in °K.
(1)
The temperature sensor then measures ΔVBE and converts to digital data. In this equation, k and q are well
defined universal constants, and N is a parameter controlled by the temperature sensor. The only other
parameter is η, which depends on the diode that is used for measurement. Since ΔVBE is proportional to both η
and T, the variations in η cannot be distinguished from variations in temperature. Since the non-ideality factor is
not controlled by the temperature sensor, it will directly add to the inaccuracy of the sensor. For the Pentium II
Intel specifies a ±1% variation in η from part to part. As an example, assume a temperature sensor has an
accuracy specification of ±3 °C at room temperature of 25 °C and the process used to manufacture the diode
has a non-ideality variation of ±1%. The resulting accuracy of the temperature sensor at room temperature will
be:
TACC = ± 3°C + (±1% of 298 °K) = ±6 °C
(2)
The additional inaccuracy in the temperature measurement caused by η, can be eliminated if each temperature
sensor is calibrated with the remote diode that it will be paired with.
PCB LAYOUT FOR MINIMIZING NOISE
In a noisy environment, such as a processor mother board, layout considerations are very critical. Noise induced
on traces running between the remote temperature diode sensor and the LM82 can cause temperature
conversion errors. The following guidelines should be followed:
1. Place a 0.1 μF power supply bypass capacitor as close as possible to the VCCpin and the recommended 2.2
nF capacitor as close as possible to the D+ and D− pins. Make sure the traces to the 2.2nF capacitor are
matched.
2. The recommended 2.2nF diode bypass capacitor actually has a range of 200pF to 3.3nF. The average
temperature accuracy will not degrade. Increasing the capacitance will lower the corner frequency where
differential noise error affects the temperature reading thus producing a reading that is more stable.
Conversely, lowering the capacitance will increase the corner frequency where differential noise error affects
the temperature reading thus producing a reading that is less stable.
3. Ideally, the LM82 should be placed within 10cm of the Processor diode pins with the traces being as straight,
short and identical as possible. Trace resistance of 1Ω can cause as much as 1°C of error.
4. Diode traces should be surrounded by a GND guard ring to either side, above and below if possible. This
GND guard should not be between the D+ and D− lines. In the event that noise does couple to the diode
lines it would be ideal if it is coupled common mode. That is equally to the D+ and D− lines.(See Figure 15)
5. Avoid routing diode traces in close proximity to power supply switching signals or filtering inductors.
6. Avoid running diode traces close to or parallel to high speed digital and bus lines. Diode traces should be
kept at least 2cm. apart from the high speed digital traces.
7. If it is necessary to cross high speed digital traces, the diode traces and the high speed digital traces should
cross at a 90 degree angle.
8. The ideal place to connect the LM82's GND pin is as close as possible to the Processors GND associated
with the sense diode.
9. Leakage current between D+ and GND should be kept to a minimum. One nano-ampere of leakage can
cause as much as 1°C of error in the diode temperature reading. Keeping the printed circuit board as clean
as possible will minimize leakage current.
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Figure 15. Ideal Diode Trace Layout
Noise coupling into the digital lines greater than 300mVp-p (typical hysteresis), overshoot greater than 500mV
above VCC, and undershoot less than 500mV below GND, may prevent successful SMBus communication with
the LM82. SMBus no acknowledge is the most common symptom, causing unnecessary traffic on the bus.
Although, the SMBus maximum frequency of communication is rather low (100kHz max) care still needs to be
taken to ensure proper termination within a system with multiple parts on the bus and long printed circuit board
traces. An R/C lowpass filter with a 3db corner frequency of about 40MHz has been included on the LM82's
SMBCLK input. Additional resistance can be added in series with the SMBData and SMBCLK lines to further
help filter noise and ringing. Minimize noise coupling by keeping digital traces out of switching power supply
areas as well as ensuring that digital lines containing high speed data communications cross at right angles to
the SMBData and SMBCLK lines.
20
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REVISION HISTORY
Changes from Revision C (March 2013) to Revision D
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 20
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PACKAGE OPTION ADDENDUM
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15-Dec-2014
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM82CIMQA/NOPB
ACTIVE
SSOP
DBQ
16
95
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
82CI
MQA
LM82CIMQAX/NOPB
ACTIVE
SSOP
DBQ
16
2500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
82CI
MQA
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
Addendum-Page 1
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PACKAGE OPTION ADDENDUM
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In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
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