A1174: Ultrasensitive Hall Effect Latch with Internally or Externally Controlled Sample and Sleep Periods for Track Ball and Scroll Wheel Applications


These parts are discontinued. Samples are no longer available. Date of status change: June 2, 2014.

The A1174 is a micro-power, Hall-effect latch for use in portable devices that employ rotational detection systems, and have a power supply voltage between 1.65 and 3.5 V. The device has a single push-pull output structure and requires no external pull-up resistor for reliable operation.

When a sufficient positive magnetic field is present on the device, the device output transitions to the low state and is latched in this state until a negative field of sufficient strength latches the device output into the high state. The latched output is ideal when using multiple sensor ICs in rotational speed and direction sensing systems (for example, track ball and scroll bar systems in portable devices).

The device includes an innovative clocking scheme that satisfies the micro-power needs of almost any application, including track balls for PDAs and cell phones. Using the EXTERNAL_CLK and DUAL_CLK pins as described in this datasheet, the device can be set into various working modes.

In Dual Clock mode, the device switches between predefined slow and fast sampling rates. The average current consumption of the device is extremely low when rotation is not detected. In External Clock mode, the user sets the clock rate for the device to achieve the required on and off times for controlling average power. This user-determined clocking also helps to achieve synchronous clocking of multiple devices. This allows a defined phase relationship between the output transitions of each device in direction detection systems.

Improved stability is made possible through dynamic offset cancellation using chopper stabilization, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress. Solid state reliability is provided by integrating, on a single silicon chip, a Hall-voltage generator, a small-signal amplifier, chopper stabilization, a latch, and a MOSFET output.

The device package is a 6-contact, 1.5 mm × 2 mm, 0.40 mm nominal overall height MLP/DFN, with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with NiPdAu leadframe plating.


Top Features

  • Micro-power latch operation
  • 1.65 to 3.5 V battery operation
  • Push-pull output eliminates the need for an external pullup resistor
  • User configured, internally or externally controlled sample and sleep periods
    • Floating the two clock pins results in the use of a fixed sampling clock internal to the sensor IC
    • Toggling the clock pins allows the user to control the sampling and sleep times of the sensor IC for extreme low power operation
  • External control of the clock pins allows the user to implement synchronous sampling of multiple sensor ICs in direction detection systems
  • Chopper stabilization
    • Superior temperature stability
    • Extremely low switchpoint drift
    • Insensitive to physical stress
  • Solid state reliability
  • Small size

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A1174EEWLT-P 6-lead MLP/DFN -40°C to 85°C Yes View Data Discontinued Contact your
local sales rep
Distributor Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.


The device package is a 6-contact, 1.5 mm × 2 mm, 0.40 mm nominal overall height MLP/DFN, with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with NiPdAu leadframe plating.

EW DFN/MLP 6 contact