Replica compensated heterogeneous DACs and methods
AssigneeMaxim Integrated Products, Inc.
InventorsRahim Chowdhury, Bo Yang, David Castaneda
Life of this patent
Estimating the term…
Abstract
Digital to analog converters having a hybrid two-stage structure. The first stage is a differential segmented current DAC controlled by the MSBs (most significant bits) of input data. The second stage is a resistor string DAC controlled by the LSBs (least significant bits) of the input data to interpolate between the differential outputs of the first stage. The resistor string is directly connected to the current DAC without the need of buffer amplifiers. Instead, a replica circuit is used to prevent the second-stage resistor string from loading the first stage current DAC. Compensation techniques are described.
Claims39
A heterogeneous digital to analog converter (DAC) for converting a multiple bit digital input to an analog output comprising:
- a differential segmented current DAC providing a differential output;
- and,
- a resistor string DAC coupled to the differential output of the differential segmented current DAC to interpolate between the differential output of the differential segmented current DAC to provide the analog output.
A heterogeneous digital to analog converter (DAC) for converting an N bit digital input to an analog output comprising:
- a decoder;
- a differential segmented current DAC coupled to the decoder and providing a differential output corresponding to the decoding of the m most significant bits of the N bit digital input;
- and,
- a resistor string DAC coupled to the differential output of the differential segmented current DAC and to the decoder to interpolate between the differential output of the differential segmented current DAC responsive to the decoding of the N−m least significant bits of the N bit digital input to provide the analog output.
A heterogeneous digital to analog converter (DAC) for converting an N bit digital input to an analog output comprising:
- a decoder;
- a differential segmented current DAC coupled to the decoder and providing a differential output corresponding to the decoding of the m most significant bits of the N bit digital input;
- a resistor string DAC coupled to the differential output of the differential segmented current DAC without amplifiers therebetween, and to the decoder to interpolate between the differential output of the differential segmented current DAC responsive to the decoding of the N−m least significant bits of the N bit digital input to provide the analog output;
- and,
- a compensation circuit canceling the effect of the current loading of the resistor string DAC on the differential segmented current DAC.
A method of converting an N bit digital signal to an analog output comprising:
- converting the m most significant bits to a differential output using a differential segmented current DAC;
- coupling a resistor string DAC directly to the differential output without an amplifier therebetween;
- canceling the effect of the current loading of the resistor string DAC on the differential segmented current DAC;
- and,
- using the resistor string DAC, interpolating the differential output using the N−m least significant bits of the N bit digital input to provide the analog output.
Dependencies are inferred from the claim text.