3422 Datasheet, PDF (6/10 Pages) Unisonic Technologies – HIGH PERFORMANCE DUAL BIPOLAR OPERATINAL AMPLIFIER

3422
HALL-EFFECT,
DIRECTION-DETECTION
SENSOR
Functional Description
The integrated circuit contains an internal voltage
regulator that powers the Hall sensors and both the
analog and digital circuitry. This regulator allows
operation over a wide supply voltage range and
provides some immunity to supply noise. The device
also contains CMOS logic circuitry that decodes the
direction of rotation of the ring magnet.
Quadrature/Direction Detection. Internal logic
circuitry provides outputs representing speed and
direction of the magnetic field across the face of the
package. For the direction signal to be appropriately
updated, a quadrature relationship must be maintained
between the ring magnet pole width*, the sensor-to-
sensor spacing, and, to a lesser extent, the magnetic
switch points. For optimal design, the sensor should
be actuated with a ring magnet pole width* two times
the sensor-to-sensor spacing. This will produce a
sinusoidal magnetic field whose period (denoted as Τ)
is then four times the sensor-to-sensor spacing. A
quadrature relationship can also be maintained for a
ring magnet that has a period that satisfies the rela-
tionship nΤ/4 = 1.5 mm, where n is any odd integer.
Therefore, ring magnets with pole-pair spacing equal
to 6 mm (n = 1), 2 mm (n = 3), 1.2 mm (n = 5), etc.
are permitted.
The response of the device to the magnetic field
produced by a rotating ring magnet is shown on page
2. Note the phase shift between the two integrated
sensors.
Outputs. The device provides three saturated
outputs: DIRECTION, E1 OUTPUT, and SPEED.
DIRECTION provides the direction output of the
sensor and is defined as OFF (high) for the direction
E1 to E2 and ON (low) for the direction E2 to E1.
SPEED provides an XOR’d output of the two sensors.
Because of internal delays, DIRECTION will always
be updated before SPEED and is updated at every
transition of E1 OUTPUT and E2 OUTPUT (internal)
allowing the use of up-down counters without the loss
of pulses.
Power-On State. At power on, the logic circuitry is
reset to provide an OFF (high) at DIRECTION and an
OFF (high) for E1 and E2 (internal) for magnetic
fields less than B_OP. This eliminates ambiguity when
the device is powered up and either sensor detects a
field between B_OP and B_RP. If either sensor is sub-
jected to a field greater than B_OP, the internal logic
will set accordingly.
* “Pole” refers to a single pole (North or South)
unless stated as “pole pair” (North and South).
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Worcester, Massachusetts 01615-0036 [phone]