The AD7401A1 is a second-order， sigma-delta （Σ-Δ） modulator that converts an analog input signal into a high speed， 1-bit data stream with on-chip digital isolation based on Analog Devices， Inc.， iCoupler? technology. The AD7401A operates from a 5 V power supply and accepts a differential input signal of ±250 mV （±320 mV full scale）。 The analog input is continuously sampled by the analog modulator， eliminating the need for external sample-and-hold circuitry. The input information is contained in the output stream as a density of ones with a data rate up to 20 MHz. The original information can be reconstructed with an appropriate digital filter. The serial I/O can use a 5 V or a 3 V supply （VDD2）。 The serial interface is digitally isolated. High speed CMOS， combined with Analog Devices， Inc.， iCoupler? technology ， means the on-chip isolation provides outstanding performance characteristics， superior to alternatives such as optocoupler devices. The part contains an on-chip reference. The AD7401A is offered in a 16-lead SOIC and has an operating temperature range of ?40°C to +125°C.