LM82

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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

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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