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LM82

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LM82 Remote Diode and Local Digital Temperature Sensor with Two-Wire Interface

Check for Samples: LM82

1FEATURES DESCRIPTION

The LM82 is a digital temperature sensor with a 2

2• Accurately Senses Die Temperature of Remote wire serial interface that senses the voltage and thus

ICs, or Diode Junctions the temperature of a remote diode using a Delta-

• On-board Local Temperature Sensing Sigma analog-to-digital converter with a digital over-

• SMBus and I2C Compatible Interface, Supports temperature detector. The LM82 accurately senses

its own temperature as well as the temperature of

SMBus 1.1 TIMEOUT external devices, such as Pentium II Processors or

• Two Interrupt Outputs: INT and T_CRIT_A diode connected 2N3904s. The temperature of any

• Register Readback Capability ASIC can be detected using the LM82 as long as a

• 7 bit Plus Sign Temperature Data Format, 1°C dedicated diode (semiconductor junction) is available

on the die. Using the SMBus interface a host can

Resolution access the LM82's registers at any time. Activation of

• 2 Address Select Pins Allow Connection of 9 a T_CRIT_A output occurs when any temperature is

LM82s on a Single Bus greater than a programmable comparator limit,

T_CRIT. Activation of an INT output occurs when any

APPLICATIONS temperature is greater than its corresponding

programmable comparator HIGH limit.

• System Thermal Management

• Computers The host can program as well as read back the state

of the T_CRIT register and the 2 T_HIGH registers.

• Electronic Test Equipment Three state logic inputs allow two pins (ADD0, ADD1)

• Office Electronics to select up to 9 SMBus address locations for the

• HVAC LM82. The sensor powers up with default thresholds

of 127°C for T_CRIT and all T_HIGHs. The LM82 is

KEY SPECIFICATIONS pin for pin and register compatible with the LM84,

Maxim MAX1617 and Analog Devices ADM1021.

• 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)

1Please 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.

2All trademarks are the property of their respective owners.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Temp

Sensor

Circuitry

D+

D-

Control

Logic

Temperature

Registers

T_CRIT

Limit

HIGH

Limit

Registers

Configuration and

Status Registers

Mfr ID

Two-Wire Serial Interface

ADD0

ADD1

SMBData

SMBCLK

8-bit '6 A/D

Converter

T_CRIT_A

INT

3.0V-3.6V

LM82

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Simplified Block Diagram

Connection Diagram

Figure 1. SSOP-TOP VIEW

See DBQ Package

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Typical Application

PIN DESCRIPTIONS

Label Pin # Function Typical Connection

floating, unconnected Left floating. PC board traces may be routed through the pads

NC 1, 5 for these pins. No restrictions applied.

VCC 2 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

D+ 3 or to the diode junction on a remote IC whose die temperature

is being sensed. When not used they should be left floating.

D−4 Diode Return Current Sink To Diode Cathode. Must float when not used.

User-Set SMBus (I2C) Address Ground (Low, “0”), VCC (High, “1”) or open (“TRI-LEVEL”)

ADD0–ADD1 10, 6 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

NC 9, 13, 15 should share the same supply as the LM82 so that the

Absolute Maximum Rating, Voltage at Any Pin, is not violated.

INT 11 Interrupt Output, open-drain Pull Up Resistor, Controller Interrupt or Alert Line

SMBus (I2C) Serial Bi- From and to Controller, Pull-Up Resistor

SMBData 12 Directional Data Line, open-

drain output

SMBCLK 14 SMBus (I2C) Clock Input From Controller, Pull-Up Resistor

Critical Temperature Alarm, Pull Up Resistor, Controller Interrupt Line or System Shutdown

T_CRIT_A 16 open-drain output

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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.

Absolute Maximum Ratings (1)

Supply Voltage −0.3 V to 6.0 V

Voltage at SMBData,

SMBCLK, T_CRIT_A & INT pins −0.5V to 6V

Voltage at Other Pins −0.3 V to (VCC + 0.3 V)

D−Input Current ±1 mA

Input Current at All Other Pins (2) 5 mA

Package Input Current (2) 20 mA

SMBData, T_CRIT_A, INT Output Sink Current 10 mA

Storage Temperature −65°C to +150°C

Soldering Information, Lead Temperature

SSOP Package (3) Vapor Phase (60 seconds) 215°C

Infrared (15 seconds) 220°C

ESD Susceptibility (4) Human Body Model 2000 V

Machine Model 250 V

(1) 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.

(2) 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.

(3) See the section titled “Surface Mount” found in a current Texas Instruments Linear Data Book for other methods of soldering surface

mount devices.

(4) Human body model, 100 pF discharged through a 1.5 kΩresistor. Machine model, 200 pF discharged directly into each pin.

Operating Ratings

Specified Temperature Range TMIN to TMAX

LM82 −40°C to +125°C

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. Typical(1) Limits(2) Units

Parameter Conditions (Limit)

Temperature Error using Local Diode (3) TA= 0 °C to +85°C, ±1 ±3 °C (max)

VCC=+3.3V

TA=−40 °C to +125°C, ±4 °C (max)

VCC=+3.3V

Temperature Error using Remote Diode (3) TA= +60 °C to +100°C, ±3 °C (max)

VCC=+3.3V

TA= 0 °C to +100°C, ±3 °C (max)

VCC=+3.3V

TA= 0 °C to +125°C, ±4 °C (max)

VCC=+3.3V

Resolution 8 Bits

1 °C

(1) Typicals are at TA= 25°C and represent most likely parametric norm.

(2) Limits are ensured to AOQL (Average Outgoing Quality Level).

(3) 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. Typical(1) Limits(2) Units

Parameter Conditions (Limit)

Conversion Time of All Temperatures (4) 460 600 ms (max)

Quiescent Current (5) SMBus (I2C) Inactive 0.500 0.80 mA (max)

D−Source Voltage 0.7 V

Diode Source Current (D+ −D−)=+ 0.65V; high level 125 μA (max)

60 μA (min)

Low level 15 μA (max)

5μA (min)

T_CRIT_A and INT Output Saturation IOUT = 3.0 mA 0.4 V (max)

Voltage

Power-On Reset Threshold On VCC input, falling edge 2.3 V (max)

1.8 V (min)

Local and Remote T_CRIT and HIGH See (6) +127 °C

Default Temperature settings

(4) 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).

(5) Quiescent current will not increase substantially with an active SMBus.

(6) Default values set at power up.

Logic Electrical Characteristics-

DIGITAL 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. Typical(1) Limits(2) Units

Symbol Parameter Conditions (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 300 mV

Hysteresis

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 2μA (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 0.4 V (max)

IOL = 6 mA 0.6

(1) Typicals are at TA= 25°C and represent most likely parametric norm.

(2) Limits are ensured to AOQL (Average Outgoing Quality Level).

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Logic Electrical Characteristics-

SMBus 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. Typical(1) Limits(2) Units

Symbol Parameter Conditions (Limit)

fSMB SMBus Clock Frequency 100 kHz (max)

10 kHz (min)

tLOW SMBus Clock Low Time 10 % to 10 % 1.3 μs (min)

25 ms (max)

tLOWMEXT Cumulative Clock Low Extend Time 10 ms (max)

tHIGH SMBus Clock High Time 90 % to 90% 0.6 μs (min)

tR,SMB SMBus Rise Time 10% to 90% 1 μs (max)

tF,SMB SMBus Fall Time 90% to 10% 0.3 ns (max)

tOF Output Fall Time CL= 400 pF, 250 ns (max)

IO= 3 mA

tTIMEOUT SMBData and SMBCLK Time Low for Reset of 25 ms (min)

Serial Interface (3) 40 ms (max)

t1SMBCLK (Clock) Period 10 μs (min)

t2, tSU;DAT Data In Setup Time to SMBCLK High 100 ns (min)

t3, tHD;DAT Data Out Stable after SMBCLK Low 300 ns (min)

TBD 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 100 ns (min)

(Stop Condition Setup)

t6, tSU;STA SMBus Start-Condition Setup Time 0.6 μs (min)

tBUF SMBus Free Time 1.3 μs (min)

(1) Typicals are at TA= 25°C and represent most likely parametric norm.

(2) Limits are ensured to AOQL (Average Outgoing Quality Level).

(3) 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

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Figure 3. SMBus TIMEOUT

Pin Name D1 D2 D3 D4 Pin Name D1 D2 D3 D4

NC (pins 1 & 5) T_CRIT_A & INT x

VCC x(1) SMBData x x

D+ x x x NC (pins 9 & 15) x x x

D−x x x x SMBCLK x x

ADD0, ADD1 x x x NC (pin 13) x x

(1) 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 user-

programmable 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

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 A0

MSB LSB

and is selected as follows:

Address Select Pin State LM82 SMBus Slave Address

ADD0 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

−1°C 1111 1111 FFh

−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

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

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.

AWrite 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

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 P3 P2 P1 P0

0 Command Select

P0-P7: Command Select

Command Select Power On Default State Register Name Register Function

Address

<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 Reserved

05h 0111 1111 127 RLHS Read Local HIGH Setpoint

06h Reserved

07h 0111 1111 127 RRHS Read Remote HIGH Setpoint

08h Reserved

09h 0000 0000 WC Write Configuration

0Ah Reserved

0Bh 0111 1111 127 WLHS Write Local HIGH Setpoint

0Ch Reserved

0Dh 0111 1111 127 WRHS Write Remote HIGH Setpoint

0Eh-2Fh Reserved for Future Use

30h-31h 0000 0000 0 Reserved

32h-34h Reserved for Future Use

35h 0000 0000 0 Reserved

36h-37h Reserved for Future Use

38h 0111 1111 127 Reserved

39h Reserved for Future Use

3Ah 0111 1111 127 Reserved

3Bh-41h Reserved for Future Use

42h 0111 1111 127 RTCS Read T_CRIT Setpoint

43h-4Fh Reserved for Future Use

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Command Select Power On Default State Register Name Register Function

Address

<P7:P0> hex <D7:D0> binary <D7:D0> decimal

50h 0111 1111 127 Reserved

51h Reserved for Future Use

52h 0111 1111 127 Reserved

53h-59h Reserved for Future Use

5Ah 0111 1111 127 WTCS Write T_CRIT Setpoint

5Ch-6Fh and F0h- Reserved for Future Use

FDh

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 Remote Remote Local INT Inversion 0

T_CRIT_A T_CRIT_A T_CRIT_A T_CRIT_A

mask mask mask mask

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.

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SNIS113D –JANUARY 2000–REVISED MARCH 2013

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

•ηis the non-ideality factor of the process the diode is manufactured on,

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SNIS113D –JANUARY 2000–REVISED MARCH 2013

• 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 ηcannot 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 ηfrom 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 1Ωcan 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.

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SNIS113D –JANUARY 2000–REVISED MARCH 2013

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

www.ti.com 15-Dec-2014

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

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.

PACKAGE OPTION ADDENDUM

www.ti.com 15-Dec-2014

Addendum-Page 2

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.

www.ti.com

PACKAGE OUTLINE

TYP-.244.228

-6.195.80[ ]

.069 MAX

[1.75]

14X .0250

[0.635]

16X -.012.008

-0.300.21[ ]

.175

[4.45]

TYP-.010.005

-0.250.13[ ]

0- 8 -.010.004

-0.250.11[ ]

(.041 )

[1.04]

.010

[0.25]

GAGE PLANE

-.035.016

-0.880.41[ ]

NOTE 3

-.197.189

-5.004.81[ ]

NOTE 4

-.157.150

-3.983.81[ ]

SSOP - 1.75 mm max heightDBQ0016A

SHRINK SMALL-OUTLINE PACKAGE

4214846/A 03/2014

NOTES:

1. Linear dimensions are in inches [millimeters]. Dimensions in parenthesis are for reference only. Controlling dimensions are in inches.

Dimensioning and tolerancing per ASME Y14.5M.

2. This drawing is subject to change without notice.

3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not

exceed .006 inch, per side.

4. This dimension does not include interlead flash.

5. Reference JEDEC registration MO-137, variation AB.

116

.007 [0.17] C A B

PIN 1 ID AREA

SEATING PLANE

.004 [0.1] C

SEE DETAIL A

DETAIL A

TYPICAL

SCALE 2.800

www.ti.com

EXAMPLE BOARD LAYOUT

.002 MAX

[0.05]

ALL AROUND

.002 MIN

[0.05]

ALL AROUND

(.213)

[5.4]

14X (.0250 )

[0.635]

16X (.063)

[1.6]

16X (.016 )

[0.41]

SSOP - 1.75 mm max heightDBQ0016A

SHRINK SMALL-OUTLINE PACKAGE

4214846/A 03/2014

NOTES: (continued)

6. Publication IPC-7351 may have alternate designs.

7. Solder mask tolerances between and around signal pads can vary based on board fabrication site.

METAL SOLDER MASK

OPENING

NON SOLDER MASK

DEFINED

SOLDER MASK DETAILS

OPENING

SOLDER MASK METAL

SOLDER MASK

DEFINED

LAND PATTERN EXAMPLE

SCALE:8X

SYMM

SEE

DETAILS

www.ti.com

EXAMPLE STENCIL DESIGN

16X (.063)

[1.6]

16X (.016 )

[0.41]

14X (.0250 )

[0.635]

(.213)

[5.4]

SSOP - 1.75 mm max heightDBQ0016A

SHRINK SMALL-OUTLINE PACKAGE

4214846/A 03/2014

NOTES: (continued)

8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate

design recommendations.

9. Board assembly site may have different recommendations for stencil design.

SOLDER PASTE EXAMPLE

BASED ON .005 INCH [0.127 MM] THICK STENCIL

SCALE:8X

SYMM

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