Isolation ICs deliver precise current, voltage measurement with low temperature drift

By Majeed Ahmad, contributing writer

The new isolated analog amplifiers, voltage sensors, and delta-sigma modulator (DSM) devices from Silicon Labs aim to provide accurate current and voltage measurement with very low drift across temperature variations. Precise current and voltage measurements are crucial in ensuring a robust operation of power control systems and protect system designs against high voltages.

The Si89xx family of isolation devices is targeted at a wide range of industrial and green-energy applications such as electric vehicle (EV) battery management and charging systems, DC/DC converters, and motor, solar, and wind turbine inverters. Silicon Labs claims that its third-generation isolation technology will keep power controllers safe across wide temperature variations with a 1,414-V working voltage and 13-kV bipolar surge.

The Si89xx portfolio of isolation ICs comprises four types of devices:

• Si892x isolated analog amplifiers are optimized for shunt-current sensing.
• Si8931/2 isolated analog amplifiers are optimized for general-purpose voltage sensing.
• Si8935/6/7 are the first isolated DSM devices that are optimized for voltage sensing.
• Si8941/6/7 isolated DSM devices are optimized for shunt-current sensing.

Take the example of automotive battery and motor/photovoltaic inverter systems that demand reliable current monitoring with robust noise immunity. Here, Si89xx isolation ICs provide up to 3× higher common-mode transient immunity (CMTI) than competing devices. The mixed-signal isolation chips also offer 75 kV/µs of immunity to fast transients and thus ensure reliable and accurate current readings in demanding industrial applications.

The current- or voltage-optimized devices with single-ended, differential, or DSM output also feature a unique low-power mode that enables a controller to manage power with a simple field-effect transistor (FET).

Key specs include:

• Typical offset error as low as ±40 µV and ±0.1% gain error
• Typical offset drift as low as ±0.15 µV/˚C and typical gain drift as low as –6 ppm/˚C
• ±62.5-mV, ±250-mV, or 2.5-V input ranges
• A stretched wide-body SOIC-8 package to support 5-kVrms isolation and 9-mm creepage/clearance and a compact narrow-body SOIC-8 to support 2.5-kVrms isolation

Samples of Si892x/3x/4x devices will be available in Q2 2019, and production quantities of all Si89xx devices are planned for Q3 2019. Evaluation kits are available.