PSoC3's Del Sig ADC is a 20-bit ADC. But the effective number of bits (ENOB) depends on the associated analog circuitry, the analog and digital routing and the electromagnetic noise pick up and your input source noise.
The effective number of bits obtained using the DVK for a 20-bit ADC is around 14.5 bits for 950 mV input provided by Agilent E3631A, when no other block inside the chip was turned on. The DVK cannot be be used reliably for high performance analog applications.
Cypress is coming up with new low cost, best analog kits in Q1, 2011 - CY8CKIT-030 for PSoC3 and CY8CKIT-050 for PSoC5.