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Hall-effect latch eases sensing process for portables

Posted: 12 Aug 2008 ?? ?Print Version ?Bookmark and Share

Keywords:sensor? clock? output? devices?

Allegro has released a new ultrasensitive, Hall-effect latch for portable equipment that use rotational detection systems having power supply voltage between 1.65V and 3.5V.

This new device carries a single push-pull output structure and does not need an external pull-up resistor in its operation. With enough positive magnetic field on the device, its output shifts to the low state and is latched in this location until a negative field with the proper strength transforms the device output into the high state. The latched output is suitable when employing multiple sensors in rotational speed and direction sensing systems in portable devices.

The A1174 device has a better clocking scheme that reduces power use in portable devices. It can be used in different working modes by using the external clock and dual clock pins. In dual clock mode, the equipment switches between predefined slow and fast sampling rates. When rotation is noticed, the device will sample in fast mode. It will change to slow sampling mode if the rotation halts.

In external clocking mode, the user clocks the device to reach the appropriate on and off time to manage average power. The manual clocking seeks to get synchronous clocking of different devices permitting a defined phase relationship between the output transitions of each device in direction detection systems. Having dual clocking or external clocking mode, the average current can be minimized by 10x over a standard micropower latch, gearing up the Allegro A1174 as major provider for power use.

New magnetic switchpoint stability is possible through dynamic offset cancellation by having chopper stabilization that reduces the residual-offset voltage normally produced by device over molding, temperature dependencies and thermal stress.

Looking closely at the communications and consumer electronics market, the new A1174 Hall-effect latch is available in a Pb-free (leadframe plating nickel palladium) 6-pin MLP microleadframe package for surface mount, with exposed pad for improved thermal dissipation.

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