Programmable Hall sensor with redundancy for safety-critical applications

January 04, 2017 // By Graham Prophet
With a dual-die construction and full die redundancy, advanced diagnostics and SENT output, the A1346 from Allegro MicroSystems Europe is a highly programmable linear Hall sensor IC that is suitable for safety-critical applications.

Full die redundancy with full diagnostics allows for a higher level of diagnostics without interruption to the application (where diagnostics would otherwise render a die temporarily unresponsive), and also allows the controller to know which die to trust when the two outputs do not agree.

 

The device incorporates dual high-precision, programmable Hall-effect linear sensor integrated circuits with open-drain outputs, for both automotive and non-automotive applications. The signal paths in the A1346 provide flexibility through external programming that allows the generation of accurate and customised outputs from an input magnetic signal.

 

The A1346 is an configurable and robust solution for the most demanding linear field sensor applications, with extensive user-reprogrammable options. Each BiCMOS monolithic integrated circuit incorporates a system-on-chip configuration that includes a Hall sensing 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, advanced output linearisation circuitry, and advanced diagnostic detection.

 

A feature of the A1346 is its ability to produce a highly linear device output for nonlinear input magnetic fields. To achieve this, it features 16-segment customer programmable linearisation, where a unique linearisation coefficient factor is applied to each segment. Linearisation coefficients are stored in a lookup table in EEPROM.

 

The A1346 contains two proprietary SENT protocols in addition to SAEJ2716: SSENT and ASENT. Both protocols enable the user to attach up to four devices on one SENT line to reduce system costs. SSENT provides sequential access to the sensors connected to the same line. SSENT provides a very low overhead method to maximise the sensor bandwidth on this single SENT line, minimising impact on system performance, while ASENT provides random access to all the sensors on the common SENT line. Both protocols allow individual sensors on the same line to enter diagnostic mode while the other sensors continue to respond to queries, allowing for the highest diagnostic