16-Bit, Isolated Sigma-Delta Modulator

The AD74021 is a high performance, second-order, Σ-Δ modulator that converts an analog input signal into a high speed, single-bit data stream, with on-chip digital isolation based on Analog Devices, Inc., iCoupler® technology. The AD7402 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 10 MHz. The original information can be reconstructed with an appropriate digital filter to achieve 87 dB signal to noise ratio (SNR) at 39 kSPS. The serial input/output can use a 3 V to 5.5 V or a 3.3 V supply (VDD2).

The serial interface is digitally isolated. High speed complementary metal oxide semiconductor (CMOS) technology, combined with monolithic transformer technology, means the on-chip isolation provides outstanding performance characteristics, superior to alternatives such as optocoupler devices. The AD7402 device is offered in an 8-lead, wide body SOIC package and has an operating temperature range of −40°C to +105°C.

Safety and regulatory approvals

* UL 1577

* VISO = 5000 V rms for 1 minute

* IEC/CSA 62368-1

* IEC/CSA 60601-1

* DIN EN IEC 60747-17 (pending)

* VIORM = 1250 VPEAK

Applications

* Shunt current monitoring

* AC motor controls

* Power and solar inverters

* Wind turbine inverters

* Data acquisition systems

* Analog-to-digital and opto-isolator replacements

1 Protected by U.S. Patents 5,952,849; 6,873,065; and 7,075,329.

* 10 MHz internal clock rate

* 16 bits, no missing codes

* Signal-to-noise ratio (SNR): 87 dB typical

* Effective number of bits (ENOB): 13.5 bits typical

* Typical offset drift vs. temperature: 1.7 µV/°C

* On-board digital isolator