Allegro's User-Programmable Linear Hall-Effect Sensor IC



Featuring built-in filtering to provide low jitter and high sensing accuracy, the new product complements Allegro's existing line of linear devices with PWM outputs by offering a device with a significantly higher carrier frequency of 2kHz, allowing it to resolve rapid changes in magnetic field. The A1356 is a high-precision user-programmable Hall-effect linear sensor with a PWM open-collector output and a PWM output duty cycle that is proportional to an applied magnetic field. It converts an analogue signal from its internal Hall sensor element to a digitally encoded PWM output signal. The coupled noise immunity of the digitally encoded PWM output is far superior to the noise immunity of an analogue output signal, particularly when the signal needs to travel over long wires within the system. The BiCMOS monolithic circuit in the A1356 integrates a Hall element, precision temperature-compensating circuitry to reduce the intrinsic sensitivity and offset drift of the Hall element, a small-signal high-gain amplifier, proprietary dynamic offset cancellation circuits, and PWM conversion circuitry. The dynamic offset cancellation circuits reduce the residual offset voltage of the Hall element, which is normally caused by device over-moulding, temperature dependencies and thermal stress. The high-frequency offset cancellation (chopping) clock allows for a greater sampling rate, which increases the accuracy of the output signal and results in faster signal processing capability. The design and manufacturing flexibility of the A1356 is realised through user-programmable gain, quiescent duty cycle, and carrier frequency. The device can be set up in a magnetic circuit and programmed with a train of serial pulses. Once the appropriate parameters have been selected, the codes can be locked for ‘one time' programming, allowing manufacturing tolerances to be reduced and the assembly process to be simplified. Power-supply operating range is from 4.5 to 18 V, and operating temperature range is from -40°C to +150°C, providing guaranteed operation in harsh automotive and industrial environments. The A1356 is targeted for automotive gear and clutch detection and position sensing, as well as key applications in the industrial market. The A1356 sensor is supplied in a lead (Pb) free, 3-pin, single in-line package (KB suffix), with 100% matt tin lead-frame plating.