Optically-Isolated Sigma-Delta Modulators Improve Efficiency

Broadcom Limited today announced a new optically-isolated sigma-delta modulator device, the Avago ACPL-C799, designed for a wide range of industrial applications including servo drives and motors. The new device features a low differential input range of +/-50 mV allowing designers to reduce power dissipation across a current-sensing shunt resistor in servo drive and motor applications.

Compared to previous generation products with an input range of +/-200 mV, the ACPL-C799 enables the use of a smaller shunt resistor with one-quarter the value, thereby eliminating 75 percent (75%) of shunt resistor’s power losses. Despite the reduced input voltage range, the device delivers superb SNR, ENOB and offset drift performance, enabling a high precision motor control in space constrained, high temperature environments.

Product highlights include: +/-50mV linear input range for low power dissipation across shunt resistor and extended range of current measurements; High performance 1-bit, 2nd order sigma-delta modulator with 77dB SNR typical, 16-bit resolution with no missing codes (12-bit ENOB), 1.3µV/ degree C maximum offset drift over temperature, and 10MHz internal clock; Robust optical isolation and insulation that supports 25kV/µs minimum common mode transient immunity (CMTI), wide creepage and clearance of 8.3 mm meeting stringent system level safety regulation, high reinforced insulation voltage of VIORM = 1414 VPEAK for reliable fail-safe protection in high voltage applications, and safety approvals from CSA, UL and IEC enabling fast system level safety clearance and time to market.

“Driven by strong growth in industrial automation, more and more servo designers are looking for a highly efficient, robust current sensing solution that will serve many servo drive models and motors at different current levels,” said Tze Siong Chong, vice president and general manager of the Isolation Products Division at Broadcom. “Expanding upon Broadcom’s market-leading optically isolated current sensing portfolio, the ACPL-C799 is the latest addition that enables higher efficiency through shunt resistor size reduction while delivering improved performance with unparalleled robustness.”

The Avago ACPL-C799 is delivered in a compact stretched SO-8 package and has an operating temperature range of -40 to +105 degrees C. Samples and production quantities of the ACPL-C799 are now available.