TMP411CD datasheet(23/61 Pages) TI2

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7.3.4 THERM (Pin 4) and ALERT/THERM2 (Pin 6)

The THERM and ALERT/THERM2 pins on the TMP411/TMP411D device are dedicated to alarm functions. The

pins are open-drain outputs that each require a pullup resistor to V+. These pins can be wire-ORed together

with other alarm pins for system monitoring of multiple sensors. The THERM pin provides a thermal interrupt

that cannot be software disabled. The ALERT pin is an earlier warning interrupt, and can be software disabled

or masked. The ALERT/THERM2 pin can be configured as a THERM2 pin, which is a second THERM pin

(Configuration Register: AL or TH bit = 1). The default setting configures pin 6 to function as an ALERT pin (AL

or TH = 0).

The THERM pin asserts low when the measured local or remote temperature is outside of the temperature

range programmed in the corresponding Local and Remote THERM Limit Register. The THERM temperature

limit range can be programmed with a wider range than that of the limit registers, which allows the ALERT pin

to provide an earlier warning than the THERM pin. The THERM alarm resets automatically when the measured

temperature falls within the THERM temperature limit range minus the hysteresis value stored in the THERM

Hysteresis Register. The permitted hysteresis values are listed in Table 8-8. The default hysteresis is 10°C.

When the ALERT/THERM2 pin is configured as a second thermal alarm (Configuration Register: bit 7 = 0, bit 5

= 1), the pin functions the same as the THERM pin, but uses the temperatures stored in the Local and Remote

Temperature High and Low Limit Registers to set the comparison range.

When ALERT/THERM2 (pin 6) is configured as an ALERT pin, (Configuration Register: bit 7 = 0, bit 5 = 0), the

pin asserts low when the measured local or remote temperature violates the range limit set by the corresponding

Local and Remote Temperature High and Low Limit Registers. The alert function configures to assert only if the

range is violated a specified number of consecutive times (either one, two, three or four times). The consecutive

violation limit is set in the Consecutive Alert Register. Required consecutive faults prevent false alerts that are

caused by environmental noise. The ALERT pin asserts low if the remote temperature sensor is open-circuit.

When the MASK function is enabled (Configuration Register: bit 7 = 1), the ALERT pin is disabled (that is,

masked). The ALERT pin resets when the controller reads the device address, as long as the condition that

caused the alert no longer persists, and the Status Register is reset.

7.3.5 Sensor Fault

The TMP411/TMP411D senses a fault at the D+ input resulting from an incorrect diode connection or an open

circuit. The detection circuitry consists of a voltage comparator that trips when the voltage at D+ exceeds (V+)

− 0.6V (typical). The comparator output is checked during a conversion. If a fault is detected, the last valid

measured temperature is the temperature measurement result, the OPEN bit (Status Register, bit 2) is set high,

and the ALERT pin asserts low if the alert function is enabled.

The D+ and D− inputs must be connected together to prevent meaningless fault warnings when the TMP411/

TMP411D remote sensor is not in use.

7.3.6 Undervoltage Lockout (TMP411 Only)

Legacy Chip: The TMP411 senses when the power-supply voltage reaches a minimum voltage level for the

ADC converter to function as shown in Figure 7-2. The detection circuitry consists of a voltage comparator

that enables the ADC converter after the power supply (V+) exceeds 2.45V (typical). The comparator output is

checked during a conversion. The TMP411 does not perform a temperature conversion if the power supply is not

valid. The last valid measured temperature is remained as the temperature measurement result. Note that the

device can still communicate with the Host when the power supply value is between Power-on-reset (POR) and

Undervoltage Lockout voltages.

New Chip: This behavior is combined with Power-on-reset (POR) and the user must consider POR instead of

Undervoltage lockout. The new chip can both communicate with the Host and do temperature conversion when

the power supply value is above POR voltage as shown in Figure 7-3. In addition, when there is no remote diode

connected, the first remote conversion must be ignored with the power supply ramp rate less than 240V/s.

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TMP411, TMP411D

SBOS383E – DECEMBER 2006 – REVISED JULY 2025

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