Monolithic isolated current sensor lowers design complexity

December 08, 2020 //By Christoph Hammerschmidt
Monolithic isolated current sensor lowers design complexity
Microelectronics engineering company Melexis (Tessenderlo, Belgium) has introduced the second-generation of isolated integrated current sensors MLX91220 (5 V) and MLX91221 (3.3 V). The Hall-effect based current sensors are qualified for use in a range of automotive and industrial applications, such as on-board chargers (OBC), DC/DC converters, power supplies, and small electric drives.

The MLX91220/21 builds on the first generation of current sensors, which integrated sensing elements and high accuracy signal conditioning with voltage isolation. The new generation current sensors, which come in a miniature SOIC8 narrow body or in a SOIC16 wide body package, improve on this by increasing the bandwidth to 300 kHz, resulting in a response time of just 2 µs. This enables higher switching frequencies and more accurate tracking in control loops. 

The MLX91220 also improves the dual on-chip overcurrent detection (OCD) function, which enables essential monitoring mechanisms using both an internal and an external feature. The internal OCD threshold can be selected in or out-of-range, with a response time of 2 µs. The external OCD threshold can be set, through an external reference voltage, within or close to the output operating range, with a typical response time of 10 µs. Both can be used in one application, to offer redundancy or detect separate conditions of short-circuit and out-of-scope.

The two new sensors offer output mode flexibility defined at the vendor’s factory trimming. Automotive applications typically prefer ratiometric analog output voltages, whereas industrial applications often rely on fixed sensitivity built around a reference voltage. The output mode is factory trimmed and selectable with intuitive product ordering codes. 

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