Two adjacent bit values switching current source between three paths
A system for processing a signal includes a detector configured to detect a two-level stream of bits; a converter configured to generate a three-level control signal based on two adjacent values within the two-level stream of bits; and a switch configured to determine which of three different paths to couple a current source to based on a value of the three-level control signal. Thus, based on adjacent values of the output stream a three-level control signal is generated which controls coupling of the current source to one of three different paths. This type of three-level digital-to-analog converter can be, for example, part of the feedback loop of an analog-to-digital converter. Similar techniques can also be utilized in a multi-segment digital-to-analog converter in which each segment of the DAC is controlled by a 3-level control signal and the DAC is implement using PMOS devices. The current source for each DAC segment is diverted to ground, the M-node, or the P-node depending on the value of the 3-level control signal.
1. A method of processing a signal, comprising:
receiving an input analog signal at a positive input and a negative input;
quantizing the analog signal to produce a two-level stream of bits;
detecting the two-level stream of bits, the two-level stream of bits having a value of 1 at a first level and a value of 0 at a second level;
generating a three-level control signal based on two adjacent values within the two-level stream of bits; and
determining to which of three different paths to couple a current source based on a value of the three-level control signal, the three different paths including a current sink, the positive input, and the negative input.
2. The method of claim 1 , in which the current source is coupled to the current sink when the two adjacent values are a 0 and a 1.
3. The method of claim 1 in which the current source is coupled to the positive input when the two adjacent values are both a 1.
4. The method of claim 1 in which the current source is coupled to the negative input when the two adjacent values are both a 0.
5. A system for processing a signal, comprising:
receiver circuitry configured to receive an input analog signal having a positive input and a negative input;
quantizer circuitry configured to quantize the input analog signal into a two-level stream of bits, the two-level stream of bits having a value of 1 at a first level and a value of 0 at a second level;
detector circuitry configured to detect the two-level stream of bits;
converter circuitry configured to generate a three-level control signal based on two adjacent values within the two-level stream of bits; and
switch circuitry configured to determine to which of three different paths to couple a current source based on a value of the three-level control signal, in which the three different paths include a current sink, the positive input, and the negative input.
6. The system of claim 5 including a delay circuit coupled between the quantizer circuitry and the detector circuitry.
7. The system of claim 5 in which the switch circuitry includes a three-way switch having the two adjacent values as input, a first output being an exclusive OR of the input, a second output being an AND of the input, and a third output being a NOR of the input.