Magnetic speed sensor with ASIL B certificate for automotive

Called A19520, A19530, and A19570, they come with ASIL B certification and measure speed and direction information.

“Until now, there have been no transmission speed sensors available designed to a certified ISO 26262 design process,” said Allegro product director Peter Wells.

Based around mixed-signal technology that the firm brands ‘SolidSpeed Digital Architecture’, they get “the widest dynamic range of air gap, distinction of vibration versus rotation, stray field immunity, and highly adaptive performance”, according to Allegro. .

• A19520 is Hall effect with a two-wire interface, has selectable output protocols, and is intended to be compatible with existing transmission designs. An EEPROM is integrated that enables factory traceability.
• A19530 is Hall effect with a three-wire interface, has signal processing, open detection, short detection capability, and selectable speed or speed-and-direction output protocols.
• A19570 is GMR detection based with a two-wire interface, “brings the same algorithmic performance as its Hall effect counterparts”, said Allegro “but at significantly larger air gaps and with flexible device orientations”. An EEPROM is integrated that enables factory traceability.

EMC protection capacitors are integrated within the package.

In some variants, a vibration detection algorithm – using analysis of the two magnetic input channels – will disable the output when vibration is detected, or indicate by output state that output data could be unreliable due to mechanical vibration.

Each part number covers a host of variants.

For example, with the A19530, speed pulses are emitted synchronised the magnetic pole transitions, with pulse width indicating which direction rotation is in. There is a third pulse width that indicates a pole transition with no direction information yet available – as might occur just as the direction of rotation changes.

• -xxxxLxx and -xxxxCxx variants, following a direction change in running mode, direction changes are immediately transmitted to the output
  In the -xxxxCxx variants, the vibration detection algorithm is only activated during calibration.
• -xxxxHxx variant, following a direction change in running mode, output pulses indicate no direction information available until direction information is validated
• -xOOOOxx option, output transitions are emitted directly after direction change event.