DDC112U.

The DDC112U is a dual input wide dynamic range charge-digitizing Analog-to-digital Converter (ADC) with 20-bit resolution. Low-level current output devices such as photo sensors can be directly connected to its inputs. Charge integration is continuous as each input uses two integrators, while one is being digitized, the other is integrating. For each of its two inputs, the ADC combines current-to-voltage conversion, continuous integration, programmable full-scale range, A/D conversion and digital filtering to achieve a precision, wide dynamic range digital result. In addition to the internal programmable full-scale ranges, external integrating capacitors allow an additional user-settable full-scale range of up to 1000pC. To provide single-supply operation, the internal A/D converter utilizes a differential input with the positive input tied to VREF. This charge is removed in proportion to the input current. At the end of the integration cycle, the remaining voltage is compared to VREF.