Allegro's Linear Hall-effect Current Sensor IC



The new ACS711 from Allegro MicroSystems Europe is a Hall-effect linear current sensor IC with a built-in overcurrent fault output that provides economical and precise AC or DC current sensing in audio, communications, white goods, and automotive applications operating at voltages up to 100V. The ACS711 consists of a linear Hall sensor circuit with a copper conduction path located near the surface of 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. The output of the device has a positive slope proportional to the current flow from the positive to the negative input pins. The internal resistance of this conductive path is typically 1.2 milliohms, providing a non-intrusive measurement interface that saves power in applications that require energy efficiency. The low-noise analogue signal path has a bandwidth of 100kHz. The ACS711 offers ±12.5A and ±25A full-scale sensing ranges, and is designed for 3.3 to 5.5 V single-supply operation. No external sense resistor is required, making the device a complete single-package solution. The overcurrent active-low fault output trips and latches at 100% of full-scale current. An integrated electrostatic shield is also included for output stability, and the ACS711 is immune to changes in conductor resistance over temperature. The ACS711 is optimised for low-side current sensing applications, although the terminals of the conductive path are electrically isolated from the sensor leads, providing sufficient internal creepage and clearance distance for low AC or DC working voltage applications. The thickness of the copper conductor allows survival of the device at up to five times the specified overcurrent condition. Typical applications include motor and pump control in white goods applications, short-circuit and overpower detection in audio applications, high-side sensing on the power supply in low-voltage domestic lighting systems, automotive door and window motor current sensing, and general low-voltage power-supply monitoring. The ACS711 is housed in a small, surface mount SOIC8 package. The lead frame is plated with 100% matt tin, which is compatible with standard lead (Pb) free PCB assembly processes. Internally, the device is lead-free, except for flip-chip high-temperature lead-based solder balls, currently exempt from RoHS requirements.