Self calibrating digital-to-analog converter
A self-calibrating digital-to-analog converter (DAC) is disclosed. The self-calibrating DAC includes an input port, a non-binary DAC, an ADC to receive an output of the non-binary DAC, a lookup table to store a plurality of calibration code and a calibration logic coupled with the non-binary DAC. The self-calibrating DAC has two modes of operations, a calibration mode and a normal operational mode. In the calibration mode, the self-calibrating DAC is configured to calculate weightages of the non-binary DAC and to calculate an offset coefficient and a gain coefficients using high precision on chip analog-to-digital converter (ADC).
1. A self-calibrating digital-to-analog converter (DAC), comprising:
an input port;
a non-binary DAC;
an ADC including a modulator to receive an output of the non-binary DAC;
a lookup table to store a plurality of calibration codes;
a calibration logic coupled with the non-binary DAC and in a calibration mode, configured to calculate bit weightages of the non-binary DAC using a calibration code in the plurality of calibration codes and to calculate an offset coefficient and a gain coefficients of the non-binary DAC; and
a conversion module to convert, in a normal mode, an input code received via the input port, to a calibrated code using the weight and the offset & gain coefficients.
2. The self-calibrating DAC of claim 1 , further including a memory to store the weight and the offset & gain coefficient that are calculated during the calibration mode.
3. The self-calibrating DAC of claim 1 , wherein the weight is calculated for a selected bit of the non-binary DAC by measuring an output of the non-binary DAC using the ADC after setting the selected input bit of the non-binary DAC to 1 and setting all other input bits of the non-binary DAC to 0.
4. The self-calibrating DAC of claim 3 , wherein the selected bit of the input calibration code is incremented to a next bit until all input bits of the raw DAC are processed using a loop.
5. The self-calibrating DAC of claim 4 , wherein the loop is executed for a number of times equal to a resolution of the raw non-binary DAC.
6. The self-calibrating DAC of claim 1 , wherein the offset & gain coefficients are calculated by inputting a zero scale voltage to the ADC to obtain a zero scale calibration code (C ZS _cal) from the ADC.
7. The self-calibrating DAC of claim 6 , wherein the offset & gain coefficients are calculated by inputting a full scale voltage to the ADC to obtain a full scale calibration code (C FS _cal) from the ADC.
8. The self-calibrating DAC of claim 7 , wherein the offset coefficient is calculated by subtracting a zero scale code from C ZS _cal, wherein the zero scale code is obtained at the output of the ADC by inputting a zero scale code from the lookup table into the non-binary DAC and measuring the DAC output using the ADC.
9. The self-calibrating DAC of claim 8 , wherein the gain coefficient is calculated using an equation (C FS _cal−C ZS _cal)/2{circumflex over ( )}N DAC _cal−l), wherein N DAC _cal is a resolution of the self-calibrating DAC.
10. A method for self-calibrating a digital-to-analog converter (DAC) having a resolution, comprising:
in a calibration mode,
calculating a weight of a non-binary DAC using an ADC;
calculating an offset coefficient of the non-binary DAC;
calculating a gain coefficient of the non-binary DAC; and
in a normal mode,
converting an input digital code to a calibrated non-binary input code using the weight, the offset coefficient and the gain coefficient.
11. The method of claim 10 , wherein the weight is calculated for a selected input bit of the non-binary DAC by measuring an output of the non-binary DAC using the ADC after setting the selected input bit of the non-binary DAC to 1 and setting all other input bits of the non-binary DAC to 0.
12. The method of claim 11 , wherein the selected input bit of the non-binary DAC is incremented to a next bit until all input bits of the non-binary DAC are processed using a loop.
13. The method of claim 12 , wherein the loop is executed for a number of times equal to a resolution of the non-binary DAC.
14. The method of claim 10 , wherein the offset coefficient and the gain coefficient are calculated by inputting a zero scale voltage to the ADC to obtain a zero scale calibration code (C ZS _cal) from the ADC.
15. The method of claim 14 , wherein the offset coefficient and the gain coefficient are calculated by inputting a full scale voltage to the ADC to obtain a full scale calibration code (C FS _cal) from the ADC.
16. The method of claim 15 , wherein the offset coefficient is calculated by subtracting a zero scale code from C ZS _cal, wherein the zero scale code is obtained at the output of the ADC by inputting a zero scale code into the non-binary DAC and measuring an output of the non-binary DAC using the ADC.
17. The method of claim 16 , wherein the gain coefficient is calculated using an equation (C FS _cal−C ZS _cal)/2{circumflex over ( )}N DAC _cal−1), wherein N DAC _cal is the resolution.
18. The method of claim 10 , wherein the converting includes reading a digital input code and multiplying the input code by the gain coefficient and adding the offset coefficient.
19. The method of claim 10 , wherein the converting includes reading a digital input code and applying the gain coefficient and the offset coefficient to the digital input code.