Allegro MicroSystems Europe has introduced a new high-speed, low-noise Hall-effect current sensor which offers 3kV RMS voltage isolation and a low-resistance current conductor for 50-100 A current measurements. The ACS756 is an open-loop current sensor with a 125 kHz bandwidth capability, and takes advantage of Allegro's low-loss leadframe technology and the fast response capability of the monolithic Hall-effect sensor IC.
The device consists of a precision, low-offset linear Hall sensor circuit with a copper conduction path located near the die. Applied current flowing through this copper conduction path generates a magnetic field which is sensed by the integrated Hall IC and converted into a proportional voltage. Device accuracy is optimised through the close proximity of the magnetic signal to the Hall transducer. A precise, proportional voltage is provided by the low-offset, chopper-stabilised BiCMOS Hall IC, which is programmed for accuracy at the factory.
The new device offers faster response times, with a 3 microsecond rise time in response to a step input current and a propagation delay of 1.6 microseconds. Output sensitivity is 20 or 40 mV/A, and noise levels of less than 9mV peak-to-peak. The ACS756 offers higher accuracy and lower drift over temperature than earlier devices, with a total output error of 0.8% at a temperature of 25°C. The 130microhm internal conductor resistance leads to low power losses, while an internal electrostatic shield effectively shunts the effects of voltage transient spikes around the sensor IC and minimises the voltage ripple on the output of the device. The result is a high performance current sensing solution suitable for motor and inverter control, power-supply control and protection, and other applications requiring high-side current sensing.
