there many kinds of calibration schemes for 1.5b/stage pipelined ADC!
if you want schematics, I am afraid there are not much on web!
some IEEE papers may be helpful:
"Digital_Domain Calibration of Multistep Analog-to-Digital Converters"
"Background Digital Calibration Techniques for Pipelined ADC's"
and so force
also u can start with allen holberg book and attached thesis