Routing Reference Voltage to 10 bit SAR ADC




Question: How does one give the reference voltage for the SAR 10 ADC in the CY8C28xxx series? Is it possible to refer the Bandgap voltage to this ADC?


Response: SAR 10 ADC is a special hardware present in some of the PSoC family. Bit 7 of SADC_CR2 selects the reference voltage for this block. A value of 1 would indicate external VRef other than Vdd. Bit6 of the same register chooses the VRef buffer for the external voltage input. On setting the above bits, one must also set the Bit 7 of SADC_CR4 which then allows the input to be referenced from P2[5]. One limitation of SAR10 ADC  is that one cannot refer the internal Bandgap voltage to this block. If Bandgap voltage is absolutely necessary in the design then one can use ADCINC10 or other variants of ADC which allow the reference of BG.