Circuit and method for calibrating a digital-to-analog converter
AssigneeMotorola, Inc.
InventorJohn Edward Hanna
Life of this patent
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Abstract
A high precision DAC (10) incorporates a low precision DAC (18) and current sources (15(A)-15(O)) whose full-scale currents are adjusted to match a reference current generated by an analog calibration circuit (28). An additional low precision DAC (20) and another current source (16) are spares that allow periodic calibration of the high precision DAC (10) to occur in the background without taking the high precision DAC (10) off-line or out of service. A thermometer code generated by a thermometer code circuit (12) is used by a thermometer mapper circuit (13) to enable the most recently calibrated current sources to generate currents having the highest probability for use by the high precision DAC (10).
Claims17
A method of operating a segmented digital-to-analog converter (DAC) having a plurality of segments, comprising the steps of:
- receiving a data signal at an input of the segmented DAC that is encoded for providing a plurality of encoded signals;
- and
- mapping the plurality of encoded signals in response to a first state of a state signal to a plurality of select signals that select a first segment for calibration and a second segment for providing a current to a summing node.
A method of calibrating a segmented digital-to-analog converter (DAC) having a plurality of segments, comprising the steps of:
- calibrating a first segment of the plurality of segments for providing a first calibrated current;
- mapping a plurality of encoded signals to a plurality of select signals that transfer the first calibrated current to a summing node and select a second segment for calibration;
- calibrating the second segment to provide a second calibrated current;
- and
- changing a state signal after calibrating the second segment that remaps the plurality of encoded signals to the plurality of select signals and transfers the second calibrated current to the summing node.
A segmented digital-to-analog converter (DAC), comprising:
- a mapper circuit having a first input coupled for receiving encoded signals, a second input coupled for receiving state selector signals that transfer one of the encoded signals to an output signal of the mapper circuit;
- a current source having an input coupled for receiving the state selector signals and an output for providing a current;
- and
- a switch having a first input coupled for receiving the output signal from the mapper circuit, a second input coupled to the output of the current source, and a first output for providing a current to an output of the segmented DAC.
Dependencies are inferred from the claim text.