DC calibration system for a digital-to-analog converter

A digital-to-analog converter with an integrated calibration system, comprising:

• a digital-to-analog converter for receiving a digital input signal on a digital input and outputting an analog output signal having an analog output level corresponding to the digital value of said digital input signal, said digital-to-analog converter including:
• an interpolation filter for increasing the sampling frequency of each digital input signal,
• a sample and hold circuit for receiving the output of said interpolation filter,
• a n-bit quantizer for converting the output of said sample and hold circuit to a n-bit digital stream,
• a n-bit digital-to-analog converter for converting the output of said n-bit quantizer to a converted analog signal, and
• a low pass analog filter for filtering the output of said n-bit digital-to-analog converter to substantially remove high frequency information therefrom that is outside of the bandwidth of said low pass analog filter;
• an offset circuit for offsetting said analog output level by an offset value;
• and
• a calibration circuit for determining said offset value in response to the generation of a calibration signal, said offset value set by said calibration circuit such that a predetermined digital input value on said digital input will result in the output of a predetermined analog output value.

A digital-to-analog converter with an integrated calibration system, comprising:

• a digital input for receiving a digital input signal;
• an interpolation section for receiving said digital input signal and increasing the sampling frequency thereof, and
• a quantizer for receiving the output of said interpolation section and converting it to a digital stream;
• a digital-to-analog convertor for converting the digital stream into a converted analog signal;
• an analog section including an analog low pass filter for filtering the converted analog signal output by said digital-to-analog converter and outputting an analog output signal to an analog output node;
• an offset register for storing a digital offset value;
• a summing junction for summing said offset value stored in said offset register with said digital input signal prior to input of said digital signal to said quantizer;
• a calibration circuit for determining said offset value in response to generation of a calibration signal, said offset value set by said calibration circuit such that a predetermined digital input value on said digital input will result in the output of a predetermined analog output value when said predetermined digital input value is summed with said offset value by said summing junction.

A method for calibrating a digital-to-analog converter, comprising the steps of:

• providing a digital input terminal;
• providing an analog output terminal;
• converting a digital input signal received on the digital input terminal to an analog output signal on the analog output terminal, the analog output level of the analog output signal corresponding to the digital value of the digital input signal;
• offsetting the analog output level by an offset value, the step of offsetting including the steps of:
• sampling the analog output level of the analog output signal when the digital input signal is disposed at a predetermined calibrating input signal;
• and
• varying the offset value until the analog output level of the output signal is substantially equal to a predetermined calibrating analog output signal when the digital input signal is forced to the predetermined calibrating input signal;
• determining the offset value in response to generation of a calibration signal such that a predetermined digital input value on the digital input terminal will result in the output of a predetermined analog output value on the analog output terminal.

A method for calibrating a digital-to-analog converter, comprising the steps of:

• providing a digital input terminal;
• providing an analog output terminal;
• converting a digital input signal received on the digital input terminal to an analog output signal on the analog output terminal, the analog output level of the analog output signal corresponding to the digital value of the digital input signal;, the step of converting including the steps of:
• filtering the digital input signal through an interpolation filter to increase the sampling frequency thereof;
• processing the output of the interpolation filter through a sample and hold circuit;
• converting the output of a sample and hold circuit to a n-bit digital stream;
• converting the n-bit digital stream to a converted analog signal;
• and
• filtering the converted analog signal with a low pass analog filter to substantially remove high frequency information therefrom that is outside the bandwidth of the low pass analog filtering step;
• offsetting the analog output level by an offset value;
• and
• determining the offset value in response to generation of a calibration signal such that a predetermined digital input value on the digital input terminal will result in the output of a predetermined analog output value on the analog output terminal.

A method for calibrating a digital-to-analog converter, comprising the steps of:

• receiving a digital input signal on a digital input;
• increasing the sampling frequency of the digital input signal;
• converting the digital signal with the increased sampling frequency to a n-bit digital stream;
• converting the n-bit digital stream to a converted analog signal;
• providing an analog low pass filter;
• filtering the converted analog signal through the analog low pass filter;
• providing an offset register;
• storing in the offset register a digital offset value;
• summing the digital offset value stored in the offset register with the digital input signal prior to conversion of the digital input signal to the n-bit digital stream;
• and
• determining the offset value in response to generation of a calibration signal, the offset value set such that a predetermined digital input value on the digital input will result in the output of a predetermined analog output value.