3213 Просмотр технического описания (PDF) - Allegro MicroSystems
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3213 Datasheet PDF : 11 Pages
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3213 AND 3214
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCHES
FUNCTIONAL DESCRIPTION
Low Average Power. Internal timing circuitry activates the
sensor for 60 µs and deactivates it for the remainder of the
period (240 µs for the A3213xx and 60 ms for the A3214xx).
A short "awake" time allows for stabilization prior to the
sensor sampling and data latching on the falling edge of the
timing pulse. The output during the "sleep" time is latched in
the last sampled state. The supply current is not affected by
the output state.
IDD(EN)
IDD(DIS)
0
PERIOD
60 µs - "AWAKE"
"SLEEP"
SAMPLE &
OUTPUT LATCHED
Dwg. WH-017-1
Chopper-Stabilized Technique. The Hall element can be
considered as a resistor array similar to a Wheatstone bridge.
A large portion of the offset is a result of the mismatching of
these resistors. These devices use a proprietary dynamic offset
cancellation technique, with an internal high-frequency clock
to reduce the residual offset voltage of the Hall element that is
normally caused by device overmolding, temperature depen-
dencies, and thermal stress. The chopper-stabilizing technique
cancels the mismatching of the resistor circuit by changing the
direction of the current flowing through the Hall plate using
CMOS switches and Hall voltage measurement taps, while
maintaing the Hall-voltage signal that is induced by the
external magnetic flux. The signal is then captured by a
sample-and-hold circuit and further processed using low-offset
bipolar circuitry. This technique produces devices that have an
extremely stable quiescent Hall output voltage, are immune to
thermal stress, and have precise recoverability after tempera-
ture cycling. This technique will also slightly degrade the
device output repeatability. A relatively high sampling
frequency is used in order that faster signals can be processed.
More detailed descriptions of the circuit operation can be
found in Technical Paper STP 97-10, Monolithic Magnetic
Hall Sensor Using Dynamic Quadrature Offset Cancellation
and Technical Paper STP 99-1, Chopper-Stabilized Amplifiers
With A Track-and-Hold Signal Demodulator.
+V
X
Dwg. EH-012-1
B
+V
—
HALL
VOLTAGE
+
Dwg. AH-011-2
Operation. The output of this device switches low (turns on)
when a magnetic field perpendicular to the Hall sensor exceeds
the operate point BOPS (or is less than BOPN). After turn-on,
the output is capable of sinking up to 1 mA and the output
voltage is VOUT(ON). When the magnetic field is reduced below
the release point BRPS (or increased above BRPN), the device
output switches high (turns off). The difference in the mag-
netic operate and release points is the hysteresis (Bhys) of the
device. This built-in hysteresis allows clean switching of the
output even in the presence of external mechanical vibration
and electrical noise.
As used here, negative flux densities are defined as less
than zero (algebraic convention) and -50 G is less than +10 G.
115 Northeast Cutoff, Box 15036
7
Worcester, Massachusetts 01615-0036 (508) 853-5000
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