ZHCSDF1 February 2015 UCD90240
PRODUCTION DATA.
UCD90240 should be powered by a 3.3-V power supply.
If internal reference is used, V33A is used as ADC reference and is assumed to be exactly 3.3 V. Any input voltage deviation from 3.3 V will introduce an error to ADC reference and thus ADC results. Therefore, the 3.3-V power supply must be tightly regulated and with very small voltage fluctuation (including voltage ripple and voltage deviation caused by load transients).
If external reference is used, the 3.3-V power supply only needs to meet the requirements specified in the Recommended Operating Conditions section and the Electrical Characteristics section.