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TMP451

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SBOS686A – JUNE 2013 – REVISED DECEMBER 2014

Additionally, a digital filter is available for the remote temperature measurements to further reduce the effect of

noise. This filter is programmable and has two levels when enabled. Level 1 performs a moving average of four

consecutive samples. Level 2 performs a moving average of eight consecutive samples. The value stored in the

remote temperature result register is the output of the digital filter, and the ALERT and THERM limits are

compared to it. This provides additional immunity to noise and spikes on the ALERT and THERM outputs. The

filter responses are shown in Figure 12. The filter can be enabled or disabled by programming the desired levels

in the digital filter register. The digital filter is disabled by default and on POR.

Figure 12. Filter Response to Impulse and Step Inputs

7.3.5 Sensor Fault

The TMP451 device can sense a fault at the D+ input resulting from incorrect diode connection. The TMP451

device can also sense an open circuit. Short-circuit conditions return a value of –64°C. The detection circuitry

consists of a voltage comparator that trips when the voltage at D+ exceeds (V+) – 0.3 V (typical). The

comparator output is continuously checked during a conversion. If a fault is detected, then OPEN (bit 2) in the

status register is set to 1.

When not using the remote sensor with the TMP451 device, the D+ and D– inputs must be connected together

to prevent meaningless fault warnings.

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