The DDC118 is a 20-bit octal channel, current-input analog-to-digital (A/D) converter. It combines both current-to-voltage and A/D conversion so that eight low-level current output devices, such as photodiodes, can be directly connected to its inputs and digitized.
For each of the eight inputs, the DDC118 provides a dual-switched integrator front-end. This design allows for continuous current integration: while one integrator is being digitized by the onboard A/D converter, the other is integrating the input current. Adjustable full-scale ranges from 12pC to 350pC and adjustable integration times from 50µs to 1s allow currents from fAs to µAs to be measured with outstanding precision. Low-level linearity is ±0.5ppm of the full-scale range and noise is 5.2ppm of the full-scale range.
Two modes of operation are provided. In Low-Power mode, total power dissipation is only 13.5mW per channel with a maximum data rate of 2.5kSPS. High-Speed mode supports data rates up to 3.125kSPS with a corresponding dissipation of 18mW per channel.
The DDC118 has a serial interface designed for daisy-chaining in multi-device systems. Simply connect the output of one device to the input of the next to create the chain. Common clocking feeds all the devices in the chain so that the digital overhead in a multi-DDC118 system is minimal.
The DDC118 is a single-supply device using a +5V analog supply and supporting a +2.7V to +5.25V digital supply. Operating over the industrial temperature range of -40°C to 85°C, the DDC118 is offered in a QFN-48 package.