Traveling pulse wave quantizer
A Traveling Pulse Wave Quantization method is provided for converting a time sensitive signal to a digital value. A first stop signal is delayed by a first time delay, a first plurality of times, to create a delayed first stop signal. A clock signal is delayed by a second time delay, a first plurality of times, to create a delayed clock signal first period. Each second time delay is associated with a corresponding first time delay, and the second time delay is greater than the first time delay. When the delayed first stop signal occurs before the delayed clock signal first period, a count of the delays is stopped and converted into a digital or thermometer value. An accurate resampled value is provided regardless of the duration in delay between the first stop signal and a second stop signal that is accepted after the first stop signal.
1. A Traveling Pulse Wave Quantizer (TPWQ) comprising:
a fast delay line having an input to accept a first stop signal followed by a second stop signal, the fast delay line comprising a first plurality of first delay elements connected in series with an output between each first delay element, where each first delay element has a first time delay;
a slow delay line having an input to accept a clock signal and comprising a first plurality of second delay elements connected in series with an output between each second delay element, where each second delay element has a second time delay greater than the first time delay;
a sampler comprising a first plurality of clocked buffers connected in series with a sample output between each clocked buffer, each clocked buffer having a signal input connected to the output of a corresponding first delay element, and a clock input connected to the output of a corresponding second delay element; and,
a resampler having an input to accept the first plurality of clocked buffer outputs, and an output to supply a first plurality of time-to-digital converter (TDC) output bits representing a time delay between the first stop signal and a first period of the first clock signal, regardless of a duration in delay between the first stop signal and the second stop signal.
2. The TPWQ of claim 1 wherein the resampler comprises a first plurality of cells ordered in an array, each cell having a signal input connected to a corresponding sample output, and a TDC output hit delayed with respect to the order of the cell in the array.
3. The TPWQ of claim 2 wherein each resampler cell comprises:
a clocked buffer having an input connected to a corresponding sample output, an input to accept a clock signal, and an output to supply a resampled signal;
a delay circuit having an input to accept the resampled signal, and an output to supply a delayed resampled signal as a TDC output bit.
4. The TPWQ of claim 3 wherein the clocked buffer supplies a resampled signal responsive to an edge of the clock signal selected from a group consisting of a positive edge and a negative edge.
5. The TPWQ of claim 3 wherein the delay circuit is a programmable delay circuit having an input to accept a delay control signal, and an output to supply the TDC output bit with a delay duration responsive to the delay control signal.
6. The TPWQ of claim 2 wherein each resampler cell comprises:
a first clocked buffer having an input connected to a corresponding sample output, an input to accept a clock signal, and an output to supply a first resampled signal responsive to a positive edge of the clock signal;
a second clocked buffer having an input connected to the corresponding sample output, an input to accept the clock signal, and an output to supply a second resampled signal responsive to a negative edge of the clock signal;
a multiplexer (MUX) having inputs accepting the first and second resampled signals, a MUX control input, and an output to supply a resampled signal selected in response to the MUX control signal; and,
a delay circuit having an input to accept the selected resampled signal, and an output to supply a delayed resampled signal as a TDC output bit.
7. The TPWQ of claim 6 wherein the delay circuit is a programmable delay circuit having an input to accept a delay control signal, and an output to supply the TDC output bit with a delay duration responsive to the delay control signal.
8. The TPWQ of claim 7 further comprising:
an incrementing device with a first plurality of control word outputs, each control word output corresponding to a resampler cell, the incrementing device supplying a MUX control signal that periodically changes in response to the order of the cell in the array, and a delay control signal that changes the delay duration in responsive to the order of the cell in the array.
9. The TPWQ of claim 8 wherein the incrementing device comprises a first plurality of summers connected in series, each summer having an output connected to supply a control word to corresponding resampler cell and a first input to accept a control word from an adjacent summer, and each summer having a second input to accept an augmentation term modifying the control word accepted at the first input.
10. The TPWQ of claim 1 wherein the fast delay line comprises:
a first fast delay line having an input to accept the first stop signal, with a first plurality of first delay elements connected in series;
a second fast delay line having an input to accept a parallel first stop signal, nominally accepted at the same time as the first stop signal, the second fast delay line having a first plurality of first delay elements connected in series;
wherein the sampler comprises:
a first sampler with a first plurality of clocked buffers, where each clocked buffer has an input connected to the output of a corresponding first delay element in the first fast delay line, and a clock input connected to the output of a corresponding second delay element of the slow delay line;
a second sampler with a first plurality of clocked buffers, where each clocked buffer has an input corrected to the output of a corresponding first delay element in the second fast delay line, and a clock input connected to the output of a corresponding second delay element of the slow delay line;
wherein the resampler comprises:
a first resampler having an input to accept the first plurality of clocked buffer outputs from the first sampler, and an output to supply a first plurality of TDC output hits representing a time delay between the first stop signal and a first period of the clock signal,
a second resampler having an input to accept the first plurality of clocked buffer outputs from the second sampler, and an output to supply a first plurality of differential TDC output hits representing a time delay between the parallel first stop signal and the first period of the clock signal; and,
a subtractor having an input to accept the TDC output hits and the differential TDC output hits, and an output to supply a difference between the TDC output hits and the differential TDC output hits.
11. A Traveling Pulse Wave Quantizer (TPWQ) analog-to-digital converter (ADC) comprising:
a voltage-to-time circuit having an input to accept an analog voltage and an output to supply a stop signal having a time delay corresponding to a sampled analog voltage level;
a fast delay line having an input to accept the stop signal and comprising a first plurality of first delay elements connected in series with an output between each first delay element, where each first delay element has a first time delay;
a slow delay line having an input to accept a clock signal and comprising a first plurality of second delay elements connected in series with an output between each second delay element, where each second delay element has a second time delay, greater than the first time delay;
a sampler comprising a first plurality of clocked buffers connected in series with a sample output between each clocked buffer, each clocked buffer having a signal input connected to the output of a corresponding first delay element, and a clock input connected to the output of a corresponding second delay element; and,
a resampler having an input to accept the first plurality of clocked buffer outputs, and an output to supply a first plurality of time-to-digital converter (TDC) output bits representing a time delay between the stop signal and a first period of the clock signal, which corresponds to the analog input signal voltage, regardless of a rate at which the analog input signal voltage is sampled.
12. The ADC of claim 11 wherein the resampler comprises a first plurality of cells ordered in an array, each cell having a signal input connected to a corresponding sample output, and a TDC output hit delayed with respect to the order of the cell in the array.
13. The ADC of claim 12 wherein each resampler cell comprises:
a clocked buffer having an input connected to a corresponding sample output, an input to accept a clock signal, and an output to supply a resampled signal;
a delay circuit having an input to accept the resampled signal, and an output to supply a delayed resampled signal as a TDC output bit.
14. The ADC of claim 13 wherein the clocked buffer supplies a resampled signal responsive to an edge of the clock signal selected from a group consisting of a positive edge and a negative edge.
15. The ADC of claim 13 wherein the delay circuit is a programmable delay circuit having an input to accept a delay control signal, and an output to supply the TDC output bit with a delay duration responsive to the delay control signal.
16. The ADC of claim 12 wherein each resampler cell comprises:
a first clocked buffer having an input connected to a corresponding sample output, an input to accept a clock signal, and an output to supply a first resampled signal responsive to a positive edge of the clock signal;
a second clocked buffer having an input connected to the corresponding sample output, an input to accept the clock signal, and an output to supply a second resampled signal responsive to a negative edge of the clock signal;
a multiplexer (MUX) having inputs accepting the first and second resampled signals, a MUX control input, and an output to supply a resampled signal selected in response to the MUX control signal; and,
a delay circuit having an input to accept the selected resampled signal, and an output to supply a delayed resampled signal as a TDC output bit.
17. A method for converting a time sensitive signal to a digital value, the method comprising:
accepting a clock signal;
accepting a first stop signal at a non-predetermined time after the acceptance of a first period of the clock signal;
delaying the first stop signal by a first time delay, a first plurality of times, to create a delayed first stop signal;
delaying the clock signal by a second time delay, a first plurality of times, to create a delayed clock signal first period, where each second time delay is associated with a corresponding first time delay, and the second time delay is greater than the first time delay;
counting the number of first time delays;
when the delayed first stop signal occurs before the delayed clock signal first period, stopping the count; and,
converting the count into a digital value, regardless of a duration in delay between the first stop signal and a second stop signal accepted after the first stop signal.
18. The method of claim 17 wherein counting the number of first time delays includes counting the number of first time delays associated with the first stop signal while simultaneously counting the number of first time delays associated with the second stop signal.
19. The method of claim 17 wherein counting the number of first time delays includes:
creating a tally of first time delays; and,
delaying the recordation of each tally in response to the order in which the tally occurs, where an initial tally is assigned a longer delay than a subsequent tally.
20. The method of claim 17 further comprising:
accepting an analog signal having a voltage;
converting the analog signal into the first stop signal; and,
wherein converting the count into the digital value includes converting the count into a digital value representing the analog signal voltage.