Analog to digital conversion circuit and method
Disclosed is a circuit for converting an analog input signal into a digital code (b 1 -b N ), comprising a delay circuit adapted to generate a periodical signal having a delay as a function of the analog input signal value; and a quantization stage for converting the delayed periodical signal into the digital code. The circuit converts an analog voltage or current into the time-domain, thus facilitating the implementation of high-speed analog-to-digital converters into submicron technologies, in particular CMOS technologies. A method of converting an analog input signal into a digital code (b 1 -b N ) is also disclosed.
1. A circuit for converting an analog input signal into a digital code, comprising:
a delay circuit configured and arranged to delay an input clock signal and generate a delayed time-varying periodical signal that periodically alters its value and has a delay as a function of an analog input signal value of the analog input signal; and
a quantization stage configured and arranged to convert the delayed time-varying periodical signal into the digital code by periodically updating a value of the digital code.
2. The circuit of claim 1 , further comprising a decoding stage for decoding the digital code into a bit pattern.
3. The circuit of claim 1 , wherein the digital code is a thermometer code.
4. The circuit of claim 1 , wherein the quantization stage comprises:
a further delay circuit adapted to receive a further periodical signal having a known phase relationship with the delayed time-varying periodical signal as an input and comprising a plurality of serially connected delay stages each adapted to produce an incrementally delayed version of the further periodical signal; and
a capture circuit having a plurality of capture stages responsive to the delayed time-varying periodical signal, each capture stage being arranged to receive a respective one of said incrementally delayed versions of the further periodical signal.
5. The circuit of claim 4 , wherein the further delay circuit is a delay-locked loop further comprising a phase detector having a first input for receiving the further periodical signal and a second input for receiving the incrementally delayed version of the further periodical signal from the final stage of the plurality of serially connected delay stages, said phase detector being arranged to generate a control signal for controlling the plurality of serially connected delay stages from the phase relationship between the respective signals on its first input and second input.
6. The circuit of claim 5 , wherein the delay circuit comprises a chain of delay stages for producing the delayed time-varying periodical signal, each stage being controlled by a further control signal, said further control signal comprising the analog input signal.
7. The circuit of claim 6 , wherein the further control signal comprises the control signal modulated by the analog input signal.
8. The circuit of claim 6 , wherein the number of delay stages in the delay circuit is half the number of delay stages in the delay locked loop.
9. The circuit of claim 4 , wherein the delay locked loop is adapted to delay the further periodical signal by an integer number of periods.
10. The circuit of claim 9 , wherein the delay circuit is adapted to delay the periodical signal by the integer number of periods in response to the analog input signal having a maximum value.
11. The circuit of claim 4 , wherein each capture stage comprises a comparator for comparing the respective one of said incrementally delayed versions of the further periodical signal with the delayed time-varying periodical signal.
12. The circuit of claim 3 , wherein each capture stage comprises a data storage element responsive to the delayed time-varying periodical signal.
13. An electronic device comprising the circuit of claim 1 .
14. A method of converting an analog input signal into a digital code, comprising:
delaying an input clock signal to generate a delayed time-varying periodical signal that periodically alters its value as a function of an analog input signal value of the analog input signal;
converting the delayed time-varying periodical signal into the digital code by periodically updating a value of the digital code.
15. The method of claim 14 , wherein said converting comprises:
generating a plurality of incrementally delayed versions of a further periodical signal having a known phase relationship with the periodical signal, and
capturing the generated incrementally delayed versions in response to the delayed time-varying periodical signal.