High accuracy sensor IC designed with low power conductors

15th August 2017

Anna Flockett

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Datasheet

A new high accuracy Hall-effect-based current sensor IC has been introduced by Allegro MicroSystems with multiple programmable fault levels intended for industrial and consumer applications with a focus on motor control and power inverter stage applications. One of the key benefits of Allegro’s ACS720 is to provide high isolation with a reduced bill of materials made possible by the proprietary IC SOIC-16W package.

The ACS720 works off a single 5V supply while maintaining an output voltage swing from 0-3V, with a stable zero current output of 1.5V.

This allows the ACS720 to operate off a 5V supply while having an output which is compatible with typical 3.3V ADCs found on many MCUs. Furthermore, the ACS720’s high PSRR rejects the noise often found on the supplies in the power section of the PCB or system, maintaining high accuracy in noisy environments.

The device has dual fault functions that are user configurable. Fast and slow fault output allow for short-circuit and overcurrent fault detection. A user-created resistor divider from the power supply of the ACS720 is used to set the fault level. The fault outputs are open drain, allowing the user to pull them up to a compatible voltage for the MCU. The open-drain outputs also allow for implementing a simple logical OR of multiple sensor fault outputs.

The ACS720 also integrates differential current sensing, which rejects external magnetic fields, greatly simplifying board layout in three-phase motor applications. Near closed-loop accuracy is achieved in this open-loop sensor IC due to Allegro’s patented, digital temperature compensation, ultimately offering a smaller and more economical solution for many current sensing applications that traditionally rely on closed-loop core based sensors.

The ACS720 is provided in a small surface-mount SOIC16 package. The leadframe is plated with 100% matt tin, which is compatible with standard lead (Pb) free printed circuit board assembly processes. Internally, the device is Pb-free, except for flip-chip high-temperature Pb based solder balls, currently exempt from RoHS. The device is fully calibrated prior to shipment from the factory.