A code-error calibrated two-step A/D converter

A direct code-error calibration technique improving the linearity of two-step or multistep ADCs (analog-to-digital converters) is implemented in the digital domain. While conventional techniques calibrate code errors in the analog domain before conversion, the proposed technique calibrates digital outputs obtained by uncalibrated ADCs after conversion. This technique reduces feedthrough, offset, and interstage gain errors simultaneously. A block diagram of a digitally calibrated two-step flash ADC is shown. The experimental ADC uses a 2- mu m n-well CMOS technology.<>