Digital voltmeter

A digital voltmeter comprising:

• a multiplexer for selecting between an input voltage and a reference voltage;
• a down-ramp generator for generating a downward ramping voltage signal;
• an up-ramp generator for generating an upward ramping voltage signal;
• a track and hold circuit for providing a selected voltage from the multiplexer to the down-ramp generator and the up-ramp generator;
• a first comparator;
• a second comparator;
• and
• a digital core,
• wherein an output of the multiplexer is coupled to an input of the track and hold circuit,
• wherein an output of the down-ramp generator and an output of the track and hold circuit are coupled to inputs of the down-ramp comparator,
• wherein an output of the up-ramp generator and the output of the track and hold circuit are coupled to inputs of the up-ramp comparator,
• wherein an output of the first comparator indicates when the downward ramping voltages signal reaches the selected voltage,
• wherein an output of the second comparator indicates when the upward ramping voltage signal reaches the selected voltage, and
• wherein the digital core is configured to control the down-ramp generator, the up-ramp generator, the multiplexer, the track and hold circuit, and the first and second comparators.

A built-in self-test (“BIST”) device of an integrated circuit (“IC”), comprising:

• a digital voltmeter, and
• a matrix for coupling one or more nodes of the IC to be sensed by the digital voltmeter for testing,
• wherein the digital voltmeter comprises:
• a multiplexer for selecting between an input voltage and a reference voltage;
• a down-ramp generator for generating a downward ramping voltage signal;
• an up-ramp generator for generating an upward ramping voltage signal;
• a track and hold circuit for providing a selected voltage from the multiplexer to the down-ramp generator and the up-ramp generator;
• a first comparator;
• a second comparator;
• and
• a digital core,
• wherein an output of the multiplexer is coupled to an input of the track and hold circuit,
• wherein an output of the down-ramp generator and an output of the track and hold circuit are coupled to inputs of the down-ramp comparator,
• wherein an output of the up-ramp generator and the output of the track and hold circuit are coupled to inputs of the up-ramp comparator,
• wherein an output of the first comparator indicates when the downward ramping voltage signal reaches the selected voltage,
• wherein an output of the second comparator indicates when the upward ramping voltage signal reaches the selected voltage, and
• wherein the digital core is configured to control the down-ramp generator, the up-ramp generator, the multiplexer, the track and hold circuit, and the first and second comparators.