Method and circuit for testing high frequency mixed signal circuits with frequency signals
AssigneeLogicVision, Inc.
InventorStephen K. Sunter
Life of this patent
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Abstract
A method of testing an analog, or mixed analog and digital, circuit designed for operation at a clock frequency comprises multiplexing a plurality of low frequency stimulus signals using a high frequency clock to produce a circuit input signal, applying the input signal to the circuit to obtain a circuit output signal; sampling the circuit output signal synchronously with the high frequency clock at a frequency equal to the clock frequency divided by the number of the low frequency signals; storing the samples and measuring properties of the signal samples to determine properties of the output signal of the circuit.
Claims40
A method for testing an analog, or mixed analog and digital, circuit that operates at a clock frequency, the method comprising:
- multiplexing a plurality of low frequency stimulus signals using a high frequency clock to produce a high frequency input stimulus signal;
- applying said input stimulus signal to a circuit under test so as to obtain a circuit output signal;
- sampling said circuit output signal synchronously with said high frequency clock at a frequency equal to the clock frequency divided by the number of said plurality of said low frequency stimulus signals to produce a sequence of samples;
- storing said samples;
- and
- measuring properties of said samples to determine properties of said circuit.
A method for testing an analog, or mixed analog and digital, circuit that operates at a clock frequency, the method comprising:
- multiplexing a plurality of low frequency stimulus signals under control of a high frequency clock to produce a high frequency input stimulus signal, at least one of said low frequency stimulus signals having an unchanging value and one of said low frequency stimulus signals having an amplitude substantially equal to the maximum amplitude that the circuit can accommodate;
- applying to said circuit a clock signal having a frequency that is the maximum frequency that the circuit can accommodate;
- applying said input stimulus signal to a circuit under test so as to obtain a circuit output signal;
- sampling said circuit output signal synchronously with said high frequency clock at a sampling frequency equal to said clock frequency divided by the number of said plurality of low frequency stimulus signals to produce a sequence of samples, said sampling including producing a sampling pulse having a duration which is significantly less than one half of the period of said clock frequency;
- storing said samples;
- and
- measuring properties of the signal samples to determine properties of said circuit under test.
A circuit for sampling an analog waveform, the circuit comprising:
- a sampling switch for sampling said analog waveform;
- a sample storage capacitance including a single capacitance and a plurality of capacitances selectably connected in parallel;
- a sampling pulse generating circuit for generating pulses having a duration significantly less than one half of the period of a sampling frequency.
A circuit for testing an analog, or mixed analog and digital, circuit that operates at a clock frequency, the circuit comprising:
- a multiplexer for multiplexing a plurality of low frequency stimulus signals;
- multiplexer control means for producing a multiplexer select signal under control of a high frequency clock to cause said multiplexer to sequentially select each said plurality of low frequency stimulus signals and produce a high frequency stimulus signal for application to a circuit under test;
- an analog sampling switch for sampling an output signal of said circuit under test in synchronism with said high frequency clock and at a frequency equal to the clock frequency divided by the number of said plurality of low frequency stimulus signals;
- a capacitance for storing samples produced by said sampling switch, said switch being connected between said output signal of said circuit under test and said capacitance;
- and
- means for measuring properties of said samples to determine properties of said circuit under test.
Dependencies are inferred from the claim text.