Digital-to-analog converter circuit
View Patent ↗A digital to analog converter including a current source for providing a master current, a first sub digital to analog converter coupled to the current source which generates a plurality of currents, and a second sub digital to analog converter coupled to at least one of the plurality of currents from the first sub digital to analog converter which generates a second plurality of currents. The digital to analog converter also includes an overlap adjustment circuit coupled with the second sub digital to analog converter which adds current. The digital to analog converter is configured to operate in a first mode for generating a sine wave with a first bit level accuracy and, when in the first mode, the overlap adjustment circuit adds no current. to the second sub digital to analog converter The digital to analog converter is configured to operate in a second mode for generating a ramp wave with a second bit level accuracy and, when in the second mode, the overlap adjustment circuit adds current to the second sub digital to analog converter. When in the second mode, the total current of the second sub digital to analog converter and the overlap converter is greater than one of the plurality of currents generated by the first sub digital to analog converter.
1. A digital to analog converter, comprising:
a current source for providing a master current;
a first sub digital to analog converter coupled to the current source, wherein the first sub digital to analog converter generates a plurality of currents;
a second sub digital to analog converter coupled to at least one of the plurality of currents from the first sub digital to analog converter, wherein the second sub digital to analog converter generates a second plurality of currents;
an overlap adjustment circuit coupled with the second sub digital to analog converter, wherein the overlap adjustment circuit adds current, wherein
the digital to analog converter is configured to operate in a first mode for generating a sine wave wherein the sine wave has a first bit level accuracy and wherein the overlap adjustment circuit adds no current to the second sub digital to analog converter,
the digital to analog converter is configured to operate in a second mode for generating a ramp wave wherein the ramp wave has a second bit level accuracy and wherein the overlap adjustment circuit adds current to the second sub digital to analog converter, and
during the second mode, the total current of the second sub digital to analog converter and the overlap converter is greater than one of the plurality of currents generated by the first sub digital to analog converter.
2. The digital to analog converter of claim 1 , wherein the currents of the first sub-digital to analog converter comprise the most significant bits and the currents of the second sub-digital to analog converter comprise the least significant bits.
3. The digital to analog converter of claim 2 , wherein the currents from the first sub-digital to analog converter comprise a plurality of currents each equal to the master current and the currents from the second sub-digital to analog converter comprise a second plurality of currents cumulatively equal to a single current generated by the first sub digital to analog converter.
4. The digital to analog converter of claim 2 , wherein the most significant bits comprise five most significant bits and the least significant bits comprise seven least significant bits.
5. The digital to analog converter of claim 4 , wherein the currents of the least significant bits are variably weighted.
6. The digital to analog converter of claim 5 , wherein the currents of the least significant bits are binary weighted currents.
7. The digital to analog converter of claim 2 , wherein during the first mode, the current of one most significant bit is greater than or equal to the current of all of the least significant bits.
8. The digital to analog converter of claim 1 , wherein the sine wave first bit level accuracy is a ten bit level accuracy and the ramp wave second bit level accuracy is a twelve bit level accuracy.
9. A frequency modulated continuous wave transceiver with a multiple mode digital to analog converter, the transceiver comprising:
an analog to digital converter;
a digital to analog converter coupled to the analog to digital converter, the digital to analog converter further comprising:
a current source for providing a master current;
a first sub digital to analog converter coupled to the current source, wherein the first sub digital to analog converter generates a plurality of currents;
a second sub digital to analog converter coupled to at least one of the plurality of currents from the first sub digital to analog converter, wherein the second sub digital to analog converter generates a second plurality of currents;
an overlap adjustment circuit coupled with the second sub digital to analog converter, wherein the overlap adjustment circuit adds current;
a voltage controlled oscillator coupled to the digital to analog converter, wherein;
the digital to analog converter is configured to operate in a first mode for generating a sine wave wherein the sine wave has a first bit level accuracy and wherein the overlap adjustment circuit adds no current to the second sub digital to analog converter,
the digital to analog converter is configured to operate in a second mode for generating a ramp wave to the voltage controlled oscillator, wherein the ramp wave has a second bit level accuracy and wherein the overlap adjustment circuit adds current to the second sub digital to analog converter, and
during the second mode, the total current of the second sub digital to analog converter and the overlap converter is greater than the single current generated by the first sub digital to analog converter.
10. The transceiver of claim 9 , wherein the digital to analog converter generates a falling ramp signal.
11. The transceiver of claim 10 , wherein the falling ramp signal has a 12 bit level accuracy.
12. The transceiver of claim 9 , wherein the digital to analog converter generates a sine wave for transmission to the analog to digital converter.
13. The transceiver of claim 12 , wherein the analog to digital converter comprises continuous time sigma delta analog to digital converters.
14. The transceiver of claim 13 , wherein the continuous time sigma delta analog to digital converters receive the generated sine wave as an element of an internal check.
15. The transceiver of claim 12 , wherein the generated sine wave first bit level accuracy is a ten bit level accuracy.