To help detect a possible sensor malfunction, the ADS114S0x provides selectable current sources to function as burn-out current sources (BOCS) using the SYS_MON[2:0] bits in the system control register (09h). Current sources are set to values of 0.2 µA, 1 µA, and 10 µA with SYS_MON[2:0] settings of 101, 110, and 111, respectively.
When enabled, one BOCS sources current to the selected positive analog input (AINP) and the other BOCS sinks current from the selected negative analog input (AINN). With an open-circuit in a burned out sensor, these BOCSs pull the positive input towards AVDD and the negative input towards AVSS, resulting in a full-scale reading. A full-scale reading can also indicate that the sensor is overloaded or that the reference voltage is absent. A near-zero reading can indicate a shorted sensor. Distinguishing a shorted sensor condition from a normal reading can be difficult, especially if an RC filter is used at the inputs. The voltage drop across the external filter resistance and the residual resistance of the multiplexer can cause the output to read a value higher than zero.
The ADC readings of a functional sensor can be corrupted when the burn-out current sources are enabled. The burn-out current sources are recommended to be disabled when performing the precision measurement, and only enabling them to test for sensor fault conditions. If the global chop mode is enabled, disable this mode before making a measurement with the burn-out current sources.