LEM Introduces Minisens ASIC Transducer in SO-8 Package for Isolated Current Measurement
LEM introduced its Minisens – a miniature, integrated circuit transducer for ac and dc isolated current measurement up to 100 KHz. The new component offers full isolation (no optocouplers required) and high sensitivity (from 20 to 200mV per Amp of primary current) with no insertion losses. To reduce manufacturing cost, it is mounted directly onto a printed cicuit board as an SMD device.
Minisens integrates, in one mixed-signal ASIC, Hall-effect sensors with a magnetic concentrator to allow direct current measurement without the need for an additional magnetic core. The non-contact measurement is claimed to enable an almost unlimited current level, eliminating the need for current flow through the device. The only limiting factor is the thermal capacities of the primary conductor. The current can be carried either by a track (or tracks) located on a PCB underneath the Minisens or by a cable or bus bar under or above the IC. The unlimited design possibilities for the primary conductor allow current measurement of 70A or higher.
Many parameters of the ASIC can be configured by on-chip non-volatile memory: adjustment of the transducer’s gain, offset, polarity, temperature drift and gain algorithm (proportional to, or independent of VDD). Two outputs are available: one filtered, to limit the noise bandwidth; and one unfiltered, to ensure a response time of less than three microseconds. The degree of electrical isolation and output sensitivity can be increased by the PCB design. For example, a primary track on the opposite side of the IC gives best isolation; a track on the same side gives the highest sensitivity. Mounted as part of a standard PCB assembly process, manufacturing costs are minimized.
The Minisens operates from a single 5V supply. To minimize power consumption, an optional input pin can be used to switch the Minisens into standby mode. The transducer is manufactured with a CMOS process and assembled in a SO8-IC package. The combination of different IC configurations and flexible PCB designs results in very versatile and attractively-priced current transducer solutions. Flexible configurations allow for previously unfeasible applications – white goods or air conditioning – that benefit from isolated current measurement. Minisens will also enable enhanced motor control to produce energy savings where other methods, such as the shunt, have traditionally been used.
