Hall effect latches offer sensitivity & output options

30th September 2015
Nat Bowers

Providing various operating magnetic thresholds, the AH37xx family of high-voltage Hall effect latch ICs from Diodes Incorporated address applications such as: controlling the commutation of BLDC motors in washing machines, dishwashers, fridge-freezers, air-conditioners, food processors, power tools and cooling fans; the measurement of speed in motors, pumps and flow meters; and contactless position sensing/indexing in printers, scanners and window blinds.

Spanning industrial and consumer applications, the AH37xx family is designed for 3 to 28V operation and integrates a reverse-blocking diode, Zener clamps on input/output pins and an output current limit to help provide protections from transients and overload. An extended temperature specification, from -40 to +125°C, and a low temperature coefficient ensure reliable operation at the switching threshold points while a 6kV ESD capability improves robustness and allows easier handling during manufacturing.

System design flexibility is achieved with different magnetic operation and release thresholds (BOP and BRP) within the family: the AH3772/4 and AH3781/2 provide high sensitivity with BOP and BRP of +25G/+40G and -25G/-40G, the medium sensitivity AH3775/6 parts are rated at +70G/+110G and-70G/-110G while the AH3777 is the least sensitive with a +140G and -140G specification. The designer is also offered a choice of output configuration, between the open-drain AH377x series and the AH378x parts, which have an internal pull-up resistor to lower BOM count and save board space.

The AH37xx Hall effect latch ICs offer excellent performance with a fast 10μs power-on time and a quick 3.75μs response time that reduces delays and commutation errors. A chopper-stabilised architecture with an internal bandgap regulator ensures temperature stability, minimises switch point drift and provides enhanced immunity to stress. The devices also have good RF noise immunity, further contributing to overall operational reliability.

In 10,000 unit quantities, the AH3772, AH3774, AH3775, AH3776, AH3777, AH3781 and AH3782 are each priced from $0.162 to $0.177. All devices are available in SOT23 and SIP3 (Bulk and Ammo pack) packages with the AH3774/5 additionally available in an SC59 package.

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