Method and apparatus for testing digital to analog and analog to digital converters

A test structure for a mixed signal system having an interconnected digital to analog converter, an analog circuit, and an analog to digital converter (ADC), the test structure comprising:

• a demultiplexer selectively connecting an output terminal of the DAC to an input terminal of the analog circuit;
• a multiplexer selectively connecting an output terminal of the analog circuit to an input terminal of the ADC;
• a test pattern generator connected to an input terminal of the DAC and generating a test pattern having a plurality of sequential values;
• and
• a test controller having an input terminal connected to an output terminal of the ADC, thereby receiving an output signal from the ADC resulting from application of the test pattern to the DAC, wherein the test controller determines a sum of the output signal over at least two sets of unique input values.

A method for testing a mixed signal system having an interconnected digital to analog converter (DAC), and an analog circuit, the method comprising the steps of:

• connecting an output terminal of the DAC to an input terminal of the analog circuit;
• applying a test pattern having a plurality of sequential values to the DAC;
• obtaining an output signal from the analog circuit, at each of a plurality of times, resulting from the application of the test pattern;
• integrating the output signals for each of at least two sets of unique test pattern input values;
• and
• calculating from the integrated output signals at least one of a gain and a non-linearity of the mixed signal system.

A method for testing a mixed signal system having an interconnected ramp generator, an analog circuit, and an analog to digital converter (ADC), the method comprising the steps of:

• connecting an output terminal of the ramp generator to an input terminal of the analog circuit, and an output terminal of the analog circuit to an input terminal of the ADC;
• applying a test pattern having a plurality of sequential values generated by the ramp generator to the analog circuit;
• obtaining an output signal from the ADC, at each of a plurality of times, resulting from the application of the test pattern;
• determining a sum of the output signals for at least two sets of unique test pattern input values;
• and
• calculating from the sums at least one of a gain and a non-linearity of the mixed signal system.

A method for testing a mixed signal system having an interconnected analog to digital converter (ADC), a digital circuit, and a digital to analog converter (DAC), the method comprising the steps of:

• connecting an output terminal of the ADC to an input terminal of the digital circuit, and an output terminal of the digital circuit to an input terminal of the DAC;
• applying a test pattern having a plurality of sequential values to the ADC;
• obtaining an output signal from the DAC, at each of a plurality of time intervals, resulting from the application of the test pattern;
• integrating the output signals for each of at least two sets of unique test pattern input values;
• and
• calculating from the integrated output signals at least one of a gain and a non-linearity of the mixed signal system.