6bits, 1Gsps Sub-Ranging Flash AD Converter

CT22502 is a configurable 3-6bits subranging ADC working at 1GSps speed.

The coarse converter that produces, at every clock cycle the Digital data used to evaluate the 3 MSB of the result and an analog residue signal to be used by the fine converters.

The C-DAC combines the input and the ADC coarse digital output to generate the residual voltage which is converted by the ADC fine to get 3 additional bits of resolution.

Both C-DAC and fine ADC work at half of the frequency and are used interleaved so that a converted value is generated at each clock cycle.

ADC Calibration can be performed in two modes:

• Auto calibration: the detected calibration code is automatically used to calibrate the ADC. This is the fastest way to calibrate the ADC but the result is affected by the noise.
• Store/retrieve mode: the calibration is performed several times and collected Data are averaged. This mode of calibration is slow but offers some noise immunity.