US 12,456,984 B2 · PVT stabilization of pipelined SAR ADC

Abstract

In a pipelined Successive Approximation Register Analog to Digital Converter, SAR ADC, a Process, Temperature, and Voltage (PVT)-dependent bias voltage is generated and used to bias the inputs of comparators in at least the first SAR stage and residual amplifier (RA). This achieves a stable biasing and an operating point of the comparators and RA input stages that is independent of PVT variations, by tracking PVT variations in such a way that variations in MOS threshold voltage and drain-source voltage are counteracted. Additionally, a threshold common mode voltage is generated from the PVT-dependent voltage, which controls the amplification duration of the RAs such that the final RA output common mode voltage is substantially equal to the PVT-dependent voltage, which is used to bias the inputs of successive SAR stages. The threshold is set to account for logic delays in terminating the amplification based on the threshold comparison, to achieve the desired common mode amplifier output. The dependency on PVT of the threshold additionally cancels temperature variation from a differential stage transconductance of the RA. Further temperature stabilization is achieved by boosting the charge output by the RA to a capacitive load during part of the amplification.

Claims34

Dependent claims

A pipeline Successive Approximation Register (SAR) Analog to Digital Converter (ADC) including at least two SAR stages and a residual amplifier (RA) between each two SAR stages, the pipeline SAR ADC comprising:

a common mode (CM) voltage generator configured to generate a CM voltage, VCM(PVT), that depends on Process, Temperature, and Voltage (PVT) characteristics of the pipeline SAR ADC;
wherein inputs of comparators in at least the first SAR stage are biased by VCM(PVT), whereby at least the first SAR stage operating point is independent of PVT variations.

Dependencies are inferred from the claim text.

PVT stabilization of pipelined SAR ADC

Life of this patent

PVT stabilization of pipelined SAR ADC

Life of this patent

Abstract

Claims34