Reference voltage diagnostic suitable for use in an automobile controller and method therefor

A diagnostic apparatus suitable for use in an automobile controller comprising:

• first and second power supply terminals respectively conducting first and second reference voltages;
• a digital sampling circuit coupled to said first and second power supply terminals and having an output terminal for providing sampled digital values of said first and second reference voltages;
• and
• a reference voltage diagnostic circuit having an input terminal coupled to said output terminal of said sampling circuit, wherein said reference voltage diagnostic circuit compares a sampled value of said first reference voltage to a sampled value of said second reference voltage, and indicates a fault in at least one of said first and second reference voltages in response to a difference between said sampled value of said first reference voltage and said sampled value of said second reference voltage being greater than a predetermined threshold.

A method of diagnosing a fault of a reference voltage in a vehicle controller, comprising the steps of:

• determining a current value of said reference voltage;
• comparing said current value of said reference voltage to a historical value of said reference voltage;
• and
• indicating a fault in said reference voltage if said current value is not within a predetermined threshold of the historical value;
• wherein said step of determining said current value of said reference voltage comprises the steps of:
• scaling said reference voltage to provide a scaled reference voltage;
• and
• converting said scaled reference voltage to a digital signal in an analog-to-digital converter.

A method of diagnosing a fault of a reference voltage in a vehicle controller, comprising the steps of:

• determining a current value of said reference voltage;
• calculating a historical value using said current value;
• comparing said current value of said reference voltage to said historical value of said reference voltage;
• and
• indicating a fault in said reference voltage if said current value is not within a predetermined threshold of the historical value;
• wherein said step of calculating said historical value based on said current value comprises the step of calculating said historical value based on said current value using a first order lag filter.

A method of diagnosing a fault of a reference voltage in a vehicle controller, comprising the steps of:

• determining said current value of said reference voltage;
• calculating a historical value using said current value;
• comparing said current value of said reference voltage to said historical value of said reference voltage;
• and
• indicating a fault in said reference voltage if said current value is not within a predetermined threshold of the historical value;
• wherein said step of calculating said historical value based on said current value comprises the step of averaging all current values over a predetermined time period.

A method of diagnosing a fault in one of multiple reference voltages in a vehicle controller, comprising the steps of:

• determining values of first and second reference voltages;
• calculating a difference between said first reference voltage and said second reference voltage;
• comparing said difference to a predetermined threshold;
• and
• indicating a fault in one of said first and second reference voltages if said difference is greater than said predetermined threshold;
• wherein said step of determining said values of said first and second reference voltages comprises the steps of:
• scaling said first reference voltage to provide a scaled first reference voltage;
• scaling said second reference voltage to provide a scaled second reference voltage;
• and
• converting said scaled first reference voltage and said scaled second reference voltage to corresponding digital signals in an analog-to-digital converter.