Systems and methods for precharging driver circuitry for an analog-to-digital converter
An ADC may include an analog front end (AFE) configured to receive an analog input signal and sample the input signal to generate an analog sampled signal comprising a plurality of analog samples and conversion circuitry configured to convert each analog sample to a respective digital sample during a conversion phase. The AFE may include an amplifier configured to receive and buffer the input signal to generate an analog output signal and sampling circuitry configured to sample each of the plurality of analog output samples onto a sampling capacitor during a sampling phase. The AFE may also include precharging circuitry configured to, during the conversion phase, track the analog input signal and store a charge on a precharging capacitor, the charge based on the analog input signal, and during a precharging transfer phase, transfer at least a portion of the charge stored on the precharging capacitor to the sampling capacitor.
1 . An analog-to-digital converter comprising:
an analog front end configured to receive an analog input signal and sample the analog input signal to generate an analog sampled signal comprising a plurality of analog samples; and
conversion circuitry configured to convert each analog sample to a respective digital sample of a digital output signal during a conversion phase of the analog-to-digital converter;
wherein the analog front end comprises:
an amplifier configured to receive and buffer the analog input signal to generate an analog output signal; and
sampling circuitry configured to sample each of the plurality of analog output samples onto a sampling capacitor of the sampling circuitry during a sampling phase of the analog-to-digital converter; and
precharging circuitry configured to:
during the conversion phase, track the analog input signal and store a charge on a precharging capacitor of the precharging circuitry, the charge based on the analog input signal; and
during a precharging transfer phase of the analog-to-digital converter, transfer at least a portion of the charge stored on the precharging capacitor to the sampling capacitor.
2 . The analog-to-digital converter of claim 1 , wherein the precharging transfer phase is overlapping with the sampling phase.
3 . The analog-to-digital converter of claim 1 , wherein the precharging transfer phase is non-overlapping with the sampling phase.
4 . The analog-to-digital converter of claim 1 , wherein the analog front end further comprises an auxiliary amplifier configured to receive and buffer the analog output signal and wherein the precharging circuitry tracks the analog input signal by tracking the output of the auxiliary amplifier.
5 . The analog-to-digital converter of claim 1 , wherein the analog front end further comprises an auxiliary amplifier configured to receive and buffer the analog input signal and wherein the precharging circuitry tracks the analog input signal by tracking the outputs of one or more of the main amplifier and the auxiliary amplifier.
6 . The analog-to-digital converter of claim 1 , wherein the precharging circuitry is further configured to:
during the conversion phase, store a respective charge on each of a plurality of precharging capacitors comprising the precharging capacitor of the precharging circuitry, the charge based on the analog input signal; and
during each of a plurality of successive precharging transfer phases comprising the precharging transfer phase, transfer the at least a portion of the charge stored on one of the plurality of precharging capacitors to the sampling capacitor.
7 . The analog-to-digital converter of claim 1 , wherein the precharging circuitry is further configured to:
during the conversion phase, track the analog output signal and store the charge differentially on the precharging capacitor and a second precharging capacitor of the precharging circuitry, the charge based on the analog output signal; and
during the precharging transfer phase, place the precharging capacitor in parallel with the sampling capacitor and the second precharging capacitor in parallel with a second sampling capacitor to transfer the at least a portion of the charge stored on the precharging capacitor to the sampling capacitor and transfer the at least a portion of the charge stored on the second precharging capacitor to the second sampling capacitor.
8 . The analog-to-digital converter of claim 1 , wherein the analog front end further comprises a delay element between an input for receiving the input analog signal and input terminals of the amplifier, and wherein the precharging circuitry is further configured to during the conversion phase, track the analog input signal by sampling the input analog signal with a delay imposed by the delay element.
9 . The analog-to-digital converter of claim 1 , wherein the analog front end further comprises a predictor circuit configured to predict, based on a current sample of the analog sampled signal, a target value for a next sample of the analog sampled signal, wherein the charge is based on the target value predicted.
10 . The analog-to-digital converter of claim 9 , wherein the predictor circuit comprises a differentiator.
11 . A method comprising, in an analog-to-digital converter having an analog front end configured to receive an analog input signal and sample the analog input signal to generate an analog sampled signal comprising a plurality of analog samples and conversion circuitry configured to convert each analog sample to a respective digital sample of a digital output signal during a conversion phase of the analog-to-digital converter, further wherein the analog front end comprises an amplifier configured to receive and buffer the analog input signal to generate an analog output signal and sampling circuitry configured to sample each of the plurality of analog output samples onto a sampling capacitor of the sampling circuitry during a sampling phase of the analog-to-digital converter:
during the conversion phase, tracking the analog input signal and storing a charge on a precharging capacitor of the precharging circuitry, the charge based on the analog input signal; and
during a precharging transfer phase of the analog-to-digital converter, transferring at least a portion of the charge stored on the precharging capacitor to the sampling capacitor.
12 . The method of claim 11 , wherein the precharging transfer phase is overlapping with the sampling phase.
13 . The method of claim 11 , wherein the precharging transfer phase is non-overlapping with the sampling phase.
14 . The method of claim 11 , further comprising tracking the analog input signal by tracking the output of an auxiliary amplifier configured to receive and buffer the analog output signal.
15 . The method of claim 11 , further comprising tracking the analog input signal by tracking the outputs of one or more of the main amplifier and an auxiliary amplifier configured to receive and buffer the analog input signal.
16 . The method of claim 11 , further comprising:
during the conversion phase, storing a respective charge on each of a plurality of precharging capacitors comprising the precharging capacitor of the precharging circuitry, the charge based on the analog input signal; and
during each of a plurality of successive precharging transfer phases comprising the precharging transfer phase, transferring the at least a portion of the charge stored on one of the plurality of precharging capacitors to the sampling capacitor.
17 . The method of claim 11 , further comprising:
during the conversion phase, tracking the analog output signal and storing the charge differentially on the precharging capacitor and a second precharging capacitor of the precharging circuitry, the charge based on the analog output signal; and
during the precharging transfer phase, placing the precharging capacitor in parallel with the sampling capacitor and the second precharging capacitor in parallel with a second sampling capacitor to transfer the at least a portion of the charge stored on the precharging capacitor to the sampling capacitor and transfer the at least a portion of the charge stored on the second precharging capacitor to the second sampling capacitor.
18 . The method of claim 11 , further comprising during the conversion phase, tracking the analog input signal by sampling the input analog signal with a delay imposed by a delay element between an input for receiving the input analog signal and input terminals of the amplifier.
19 . The method of claim 11 , further comprising predicting, based on a current sample of the analog sampled signal, a target value for a next sample of the analog sampled signal, wherein the charge is based on the target value predicted.
20 . The method of claim 19 , wherein predicting the target value comprises using a differentiator.