A1174 Datasheet, PDF (1/13 Pages) Allegro MicroSystems – Ultrasensitive Hall Effect Latch with Internally or Externally Controlled Sample and Sleep Periods for Track Ball and Scroll Wheel Applications

A1174
Ultrasensitive Hall Effect Latch
with Internally or Externally Controlled Sample and Sleep Periods
for Track Ball and Scroll Wheel Applications
Features and Benefits
▪ Micro-power latch operation
▪ 1.65 to 3.5 V battery operation
▪ Push-pull output eliminates the need for an external pull-
up 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
▫ Toggling the clock pins allows the user to control the
sampling and sleep times of the sensor for extreme low
power operation
▪ External control of the clock pins allows the user to
implement synchronous sampling of multiple sensors in
direction detection systems
▪ Chopper stabilization
▫ Superior temperature stability
▫ Extremely low switchpoint drift
▫ Insensitive to physical stress
▪ Solid state reliability
▪ Small size
Package: 6-contact MLP/DFN (suffix EW)
1.5 mm × 2 mm × 0.40 mm
Description
TheA1174 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 sensors 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
Not to scale
Continued on the next page…
A1174-DS
+B
Magnetic Flux
Density ⁰
–B
+V
A1174 Output
B_OP
B_RP
B_OP
B_RP
B_OP
B_RP
On Off On Off On
Figure 1. Timing diagram for output switching