AATS643LSH_06 Datasheet, PDF (13/16 Pages) Allegro MicroSystems – Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor with Continuous Update

ATS643LSH
Self-Calibrating, Zero-Speed Differential
Gear Tooth Sensor with Continuous Update
Undervoltage Lockout. When the supply voltage falls
below the minimum operating voltage, V_CC(UV), I_CC goes high
and remains high regardless of the state of the magnetic gradi-
ent from the target. This lockout feature prevents false signals,
caused by undervoltage conditions, from propagating to the
output of the sensor.
Power Supply Protection. The device contains an on-chip
regulator and can operate over a wide V_CC range. For devices
that need to operate from an unregulated power supply, transient
protection must be added externally. For applications using a
regulated line, EMI/RFI protection may still be required. Contact
Allegro Microsystems for information on the circuitry needed
for compliance with various EMC specifications. Refer to fig-
ure 7 for an example of a basic application circuit.
Automatic Gain Control (AGC). This feature allows the
device to operate with an optimal internal electrical signal,
regardless of the air gap (within the AG specification). At
power-on, the device determines the peak-to-peak amplitude
of the signal generated by the target. The gain of the sensor is
then automatically adjusted. Figure 8 illustrates the effect of this
feature.
Automatic Offset Adjust (AOA). The AOA is patented cir-
cuitry that automatically cancels the effects of chip, magnet, and
installation offsets. (For capability, see Dynamic Offset Cancel-
lation, in the Operating Characteristics table.) This circuitry is
continuously active, including both during power-on mode and
running mode, compensating for any offset drift. Continuous
operation also allows it to compensate for offsets induced by
temperature variations over time.
Assembly Description. The ATS643 is integrally molded
into a plastic body that has been optimized for size, ease of
assembly, and manufacturability. High operating temperature
materials are used in all aspects of construction.
(Optional)
1
2
3
ATS643
(Optional)
4
100 Ω
VCC
0.01 μF
Ferrous Target
Mechanical Profile
V+
Internal Differential
Analog Signal
Response, without AGC
V+
Internal Differential
Analog Signal
Response, with AGC
AG_Large
AG_Small
AG_Small
AG_Large
Figure 7. Typical basic circuit for proper device operation.
Figure 8. Automatic Gain Control (AGC). The AGC function corrects for
variances in the air gap. Differences in the air gap cause differences in
the magnetic field at the device, but AGC prevents that from affecting
device performance, a shown in the lowest panel.
Allegro MicroSystems, Inc.
13
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com