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LM82

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SNIS113D –JANUARY 2000–REVISED MARCH 2013

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

Check for Samples: LM82

FEATURES

DESCRIPTION

The LM82 is a digital temperature sensor with a 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 I

C 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)

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.

2All 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.

Summary of content (25 pages)

PAGE 1
LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 LM82 Remote Diode and Local Digital Temperature Sensor with Two-Wire Interface Check for Samples: LM82 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com Figure 5. Temperature-to-Digital Transfer Function (Non-linear scale for clarity) Figure 6.
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LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 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).
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com SNIS113D – JANUARY 2000 – REVISED MARCH 2013 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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).
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LM82 www.ti.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com 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.
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LM82 SNIS113D – JANUARY 2000 – REVISED MARCH 2013 www.ti.com 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.
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LM82 www.ti.com 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 ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 24-Oct-2013 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.
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