Isolated ICs exhibit low temperature drift

Isolated analogue amplifiers, voltage sensors and delta-sigma modulator (DSM) devices introduced by Silicon Labs have been designed to provide accurate current and voltage measurement with very low drift across temperature.

The Si89xx family of devices is based on Silicon Labs’ third-generation isolation technology. The isolated ICs provide flexible voltage, current, output and package options to help reduce the bill of materials and also to reduce the board space required for a range of industrial and green-energy applications, says Silicon Labs. Target applications include electric vehicle (EV) battery management and charging systems, DC/DC converters, and motor, solar and wind turbine inverters.

To maximise efficiency and to respond quickly to faults or changes in load, system controllers require current and voltage information from high-voltage rails. Silicon Labs’ third-generation isolation technology keeps controllers safe across wide temperature variations with 1414V working voltage and 13kV bipolar surge, which exceeds industry requirements.

There are four product categories in the Si89xx family. The Si892x isolated analogue amplifiers are optimised for shunt-current sensing, the Si8931/2 isolated analogue amplifiers are for general-purpose voltage sensing, the Si8935/6/7 isolated DSM devices are claimed to be an industy first and are optimised for voltage sensing, and finally, the Si8941/6/7 isolated DSM devices are optimised for shunt-current sensing.

According to the company, its isolation products continue to replace traditional optocouplers and outperform competing digital isolators, enabling higher surge performance, reliability and safety for system designs that need to be protected from high voltages.

Automotive battery and motor/photovoltaic inverter systems require reliable current monitoring with robust noise immunity. The Si89xx devices provide up to three times higher common-mode transient immunity (CMTI) than competing products, claims Silicon Labs. They exhibit 75kV/micro seconds immunity to fast transients to ensure reliable and accurate current readings in demanding industrial applications. The Si89xx family also supports a fail-safe indication to the host controller if the high-side supply voltage is not detected.

The Si89xx devices provide typical offset error as low as ±40 microV and ±0.1 per cent gain error. Typical offset drift is as low as ±0.15 microV/ degrees C and typical gain drift as low as –6 ppm/ degrees C for accuracy across temperature. They are also claimed to offer the industry’s highest typical signal-to-noise ratio (SNR) at up to 90dB. A low-power mode automatically reduces current draw on one side of the isolation barrier to approximately 1mA whenever voltage is removed from the other side, enabling a controller to manage power with a simple FET.

Advanced samples of Si892x/3x/4x devices in wide-body SOIC-8 packages are available now, and advanced samples of the devices in narrow-body SOIC-8 packages are planned to be available in Q2. Production quantities of all Si89xx devices are planned for Q3.

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