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Isolation amps boast high gain accuracy, low temp drift

Posted: 11 May 2010 ?? ?Print Version ?Bookmark and Share

Keywords:isolation amplifier? ADC? motor control?

ACPL-C79x isolation amps

Avago Technologies is offering three miniature precision isolation amplifiers with increased accuracy, bandwidth and high insulation made possible by proprietary optical isolation technology.

Based on sigma-delta ADCs and chopper stabilized amplifiers, the new isolation amplifiers feature high gain accuracy, low temperature drift, 3.3V/5V output supply operation and a wide -40 to +105C operating temperature range. These features are delivered in a stretched SO-8 package that has a footprint 30 percent smaller than the standard DIP-8 package. When mounted on a PCB, it occupies a space that is a fraction of that for a traditional Hall Effect or transformer based isolation amplifier.

The series is implemented with a fully differential circuit topology with a gain accuracy of 0.5 percent (ACPL-C79B), 1 percent (ACPL-C79A), and 3 percent (ACPL-C790). Normalized gain drift is -50 ppm/C. With a 200kHz bandwidth and 1.6?s response time, the ACPL-C79x captures transients during short circuit and overload conditions. Operating from a single 5V supply, the isolation amplifier series features an excellent nonlinearity of 0.05 percent and a SNR of 60dB.

The ACPL-C79x high common-mode transient immunity of 15kV/?s provides the precision and stability needed to accurately monitor current in high noise motor control environments. This ensures smoother control with less "torque ripple" in many motor control applications.

Widely used for motor phase and rail current sensing, servo motor drive, switching power supply feedback isolation, DC link voltage monitoring, inverter current sensing and switching power supply feedback isolation, the ACPL-C97x targets industrial automation and instrumentation, renewable energy, and HVAC markets.

In a typical motor drive application, currents through a small value current sense resistor cause a voltage drop that is sensed by the ACPL-C79x isolation amplifier and a differential output voltage, proportional to the current, is created on the output side of the isolation barrier.

The ACPL-C79x isolation amplifiers are available in a compact 8-pin stretched SO-8 package for automatic SMT assembly and are RoHS-compliant. All devices operate over a very wide temperature range, -40C to +105C.

In order to achieve high insulation ratings, package creepage and clearance is 8mm and distance-through-isolation, DTI, is 0.5mm.

Avago's ACPL-C79B, ACPL-C79A and ACPL-C790 are priced at $6.25, $5 and $3.75, respectively, each in 10,000-piece quantities.

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