Background sensor diagnostic for multi-channel ADC

A digital sensor system, the digital sensing device comprising:

• a sensor configured to sense a physical state or condition, and output an analog signal corresponding to a sensed physical stat or condition;
• a sensor analog front end (AFE) configured to receive the analog signal from the sensor, the AFE including:
• a plurality of input channels receiving one or more analog input signals from the sensor
• an input multiplexer configured to select a pair of input channels from the plurality of input channels and to connect the selected input channels to output nodes;
• an input buffer comprising a first input terminal and a second input terminal coupled to respective output nodes of the input multiplexer, the input buffer configured to generate buffered signals from the analog input signals selected by the input multiplexer;
• an analog-to-digital converter configured to receive the buffered signals and to generate digital values indicative of the selected analog input signals;
• and
• a sensor diagnostic system configured to detect sensor fault conditions, comprising:
• a first burnout current source providing a first burnout current and a second burnout current source providing a second burnout current, the first and second burnout current sources being multiplexed by the input multiplexer to be switchably connected to a selected input channel pair of the plurality of input channels, the input multiplexer being configured to apply the first and second burnout currents to an input channel pair that is either currently selected or not currently selected by the input multiplexer independent of the selection of a pair of input channels;
• and
• a near-rail detector coupled to the first and second input terminals of the input buffer and configured to detect when a voltage on one of the first and second input terminals of the input buffer is near a positive power supply or near a negative power supply and to generate a signal indicative of a near-rail condition.

An sensor analog front end (AFE) including a plurality of input channels receiving one or more analog input signals from a sensor, the sensor AFE comprising:

• an input multiplexer configured to select a pair of input channels from the plurality of input channels and to connect the selected input channels to output nodes;
• an input buffer comprising a first input terminal and a second input terminal coupled to respective output nodes of the input multiplexer, the input buffer configured to generate buffered signals from the analog input signals selected by the input multiplexer;
• an analog-to-digital converter configured to receive the buffered signals and to generate digital values indicative of the selected analog input signals;
• and
• a sensor diagnostic system configured to detect sensor fault conditions, including a first burnout current source providing a first burnout current and a second burnout current source providing a second burnout current, the first and second burnout current sources being multiplexed by the input multiplexer to be switchably connected to a selected input channel pair of the plurality of input channels, the input multiplexer being configured to apply the first and second burnout currents to an input channel pair that is either currently selected or not currently selected by the input multiplexer independent of the selection of a pair of input channels.