Time-to-voltage converter using correlated double sampling

Patent metadata

Field	Value
Publication number	US-2020007136-A1
Application number	US-201816022188-A
Country	US
Kind code	A1
Filing date	Jun 28, 2018
Priority date	Jun 28, 2018
Publication date	Jan 2, 2020
Grant date	—

Abstract

A time-to-voltage converter is configured to generate an output voltage signal and a correlated reference voltage signal. The time-to-voltage converter includes a current source configured to generate a bias current through a current source output node. The time-to-voltage converter includes a first switched-capacitor circuit coupled to the current source output node and configured to generate the output voltage signal based on an input time signal and the bias current during a first interval. The time-to-voltage converter includes a second switched-capacitor circuit coupled to the current source output node and configured to generate the correlated reference voltage signal based on a reference time signal and the bias current during a second interval. The first interval and the second interval are non-overlapping intervals.

First claim

1 . An apparatus comprising:
a time-to-voltage converter configured to generate an output voltage signal and a correlated reference voltage signal, wherein the time-to-voltage converter comprises:
a current source configured to generate a bias current through a current source output node;
a first switched-capacitor circuit coupled to the current source output node and configured to generate the output voltage signal based on an input time signal and the bias current during a first interval; and
a second switched-capacitor circuit coupled to the current source output node and configured to generate the correlated reference voltage signal based on a reference time signal and the bias current during a second interval, the first interval and the second interval being non-overlapping intervals.

2 . The apparatus, as recited in claim 1 , wherein the second switched-capacitor circuit comprises:
a reference capacitor configured to sample a current source output node to develop a reference voltage during the second interval; and a hold capacitor selectively coupled in parallel with the reference capacitor and configured to hold the reference voltage outside the second interval.

3 . The apparatus, as recited in claim 1 , further comprising:
a third switched-capacitor circuit configured to generate a second correlated reference voltage signal based on a second reference time signal and the bias current during a third interval, the third interval and the second interval being non-overlapping intervals; and a differential pair of reference voltage terminals, a positive terminal of the differential pair of reference voltage terminals coupled to receive the correlated reference voltage signal and a negative terminal of the differential pair of reference voltage terminals coupled to receive the second correlated reference voltage signal to provide transient voltage neutralization in a circuit coupled to the differential pair of reference voltage terminals.

4 . The apparatus, as recited in claim 1 , wherein the output voltage signal has a selectable slew rate.

5 . The apparatus, as recited in claim 1 , wherein the current source comprises:
a switched-capacitor circuit; and a voltage-to-current converter configured to generate an output current based on a reference voltage signal and a feedback signal.

6 . The apparatus, as recited in claim 5 , wherein the current source further comprises:
a switched-capacitor resistor configured to vary the bias current as a function of an input period, the switched-capacitor resistor being coupled to a first node, the feedback signal being based on a current through the first node.

7 . The apparatus, as recited in claim 5 , wherein the feedback signal is the correlated reference voltage signal.

8 . The apparatus, as recited in claim 1 , wherein the first switched-capacitor circuit comprises:
a voltage-to-current converter configured to generate an output current based on a reference voltage signal and a feedback signal.

9 . The apparatus, as recited in claim 1 , wherein the time-to-voltage converter is configured as part of a first order sigma-delta modulator-based time-to-digital converter and the first switched-capacitor circuit includes a capacitor that stores a residue charge.

10 . The apparatus, as recited in claim 1 , further comprising:
a phase detector configured to generate the input time signal indicative of an input interval; and an analog-to-digital converter configured to generate a digital code corresponding to the output voltage signal using the correlated reference voltage signal, wherein the phase detector, the time-to-voltage converter, and the analog-to-digital converter are configured as a time-to-digital converter.

11 . The apparatus, as recited in claim 1 , further comprising:
a digital-to-analog converter configured to use the correlated reference voltage signal to generate the input time signal in response to an input digital code and a reference time signal; a comparator configured to generate an output time signal in response to a comparison of the output voltage signal and a threshold voltage level of the comparator; and wherein the time-to-voltage converter, the digital-to-analog converter, and the comparator are configured as a digital-to-time converter.

12 . A method comprising:
generating a bias current; generating an output voltage signal that is linearly related to an input time signal based on the bias current during a first interval; generating a correlated reference voltage signal, generation of the correlated reference voltage signal comprising:
sampling the bias current during a second interval to generate a bias current sample; and
updating the correlated reference voltage signal using the bias current sample to generate the correlated reference voltage signal,
wherein the first interval and the second interval are non-overlapping periodic intervals of a periodic signal.

13 . The method, as recited in claim 12 , further comprising:
converting an input interval between a time representation and a digital signal representation based on the output voltage signal and the correlated reference voltage signal.

14 . The method, as recited in claim 12 , further comprising:
generating a second correlated reference voltage signal, generation of the second correlated reference voltage signal comprising:
sampling the bias current during a third interval of the periodic signal to generate the second correlated reference voltage signal; and
holding the second correlated reference voltage signal outside the third interval.

15 . The method, as recited in claim 12 , further comprising:
generating a second correlated reference voltage signal that is linearly related to a second reference time signal based on the bias current; and neutralizing transient voltages in a circuit by providing the correlated reference voltage signal and the second correlated reference voltage signal to a differential pair of reference voltage terminals of the circuit, a positive terminal of the differential pair of reference voltage terminals coupled to receive the correlated reference voltage signal and a negative terminal of the differential pair of reference voltage terminals coupled to receive the second correlated reference voltage signal.

16 . The method, as recited in claim 12 , wherein generating the bias current comprises:
converting a reference voltage to an output current based in response to a feedback signal.

17 . The method, as recited in claim 16 , wherein generating the bias current further comprises:
varying the bias current and the feedback signal as a function of an input period.

18 . The method, as recited in claim 16 , wherein the feedback signal is the correlated reference voltage signal.

19 . The method, as recited in claim 12 , wherein generating the correlated reference voltage signal further comprises:
generating an output current based on a reference voltage signal and a feedback signal.

20 . A data converter comprising:
a time-to-voltage converter configured to generate an output voltage signal in response to an input interval and a correlated reference voltage signal in response to a reference interval, wherein the data converter is a time-to-digital converter or a digital-to-time converter, wherein if the data converter is the time-to-digital converter, the data converter further comprises:
a phase detector configured to generate the input interval in response to a first input signal and

Assignees

• Silicon Lab Inc

Inventors

• Caffee Aaron J
• Sonntag Jeffrey L
• Drost Brian G
• Kratyuk Volodymyr

Classifications

• H03K5/24

  the characteristic being amplitude · CPC title

• G04F10/005 Primary

  Time-to-digital converters [TDC] (analog-to-digital converters with intermediate conversion to time or phase H03M1/50, H03M1/60) · CPC title

• H03M1/06 Primary

  Continuously compensating for, or preventing, undesired influence of physical parameters (periodically, {e.g. by using stored correction values,} H03M1/10) · CPC title