16-Bit, Isolated Sigma-Delta Modulator, LVDS Interface

The AD74051 is a high performance, second-order, Σ-Δ modulator that converts an analog input signal into a high speed, single-bit LVDS data stream, with on-chip digital isolation based on Analog Devices, Inc., iCoupler® technology. The AD7405 operates from a 4.5 V to 5.5 V (VDD1) power supply and accepts a differential input signal of ±250 mV (±320 mV full-scale). The differential input is ideally suited to shunt voltage monitoring in high voltage applications where galvanic isolation is required.

The analog input is continuously sampled by a high performance analog modulator, and converted to a ones density digital output stream with a data rate of up to 20 MHz. The original information can be reconstructed with an appropriate digital filter to achieve 88 dB SNR at 78.1 kSPS. The LVDS input/output can use a 3 V to 5.5 V supply (VDD2).

The LVDS interface is digitally isolated. The LVDS interface technology, combined with monolithic transformer technology, means the on-chip isolation provides outstanding performance characteristics, superior to alternatives such as optocoupler devices. The AD7405 device is offered in a 16-lead, wide-body SOIC package and has an operating temperature range of −40°C to +125°C.

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Applications

* Shunt current monitoring

* AC motor controls

* Power and solar inverters

* Wind turbine inverters

* Data acquisition systems

* Analog-to-digital and opto-isolator replacements

* 5 MHz to 20 MHz external clock input rate

* 16 bits, no missing codes

* Signal-to-noise ratio (SNR): 88 dB typical

* Effective number of bits (ENOB): 14.2 bits typical

* Typical offset drift vs. temperature: 1.6 μV/°C typical

* Low voltage differential signaling (LVDS) interface

* On-board digital isolator