ATS616LSG Allegro MicroSystems, ATS616LSG Datasheet - Page 11

• Manufacturer Part Number: ATS616LSG
• Description: Dynamic Self-Calibrating Peak-Detecting Differential Hall Effect Gear Tooth Sensor
• Manufacturer: Allegro MicroSystems

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Peak Detecting vs. AC-Coupled Filters.
(normal ac coupling) is a commonly used technique for eliminat-
ing circuit offsets. However, ac coupling has errors at power-on
because the filter circuit needs to hold the circuit zero value
even though the circuit may power-on over a large signal. Such
filtering techniques can only perform properly after the filter
has been allowed to settle, which typically takes longer than 1s.
Also, high-pass filter solutions cannot easily track rapidly chang-
ing baselines, such as those caused by eccentricities. (The term
baseline refers to a 0 G differential field, where each Hall-effect
element is subject to the same magnetic field strength; see figure
3.) In contrast, peak detecting designs switch at the change in
slope of the differential signal, and so are baseline-independent
both at power-on and while running.
Peak Detecting vs. Zero-Crossing Reference.
ferential zero-crossing sensors are susceptible to false switching
due to off-center and tilted installations that result in a shift of
the baseline that changes with air gap. The track-and-hold peak
detection technique ignores baseline shifts versus air gaps and
provides increased immunity to false switching. In addition,
using track-and-hold peak detection techniques, increased air
gap capabilities can be expected because peak detection utilizes
the entire peak-to-peak signal range, as compared to zero-cross-
ing detectors, which switch at half the peak-to-peak signal.
Power-On Operation.
(output voltage high), irrespective of the magnetic field condi-
tion. The power-up time of the circuit is no greater than 500 μs.
The circuit is then ready to accurately detect the first target edge
that results in a high-to-low transition of the device output.
Undervoltage Lockout (UVLO).
ATS616LSG-DS, Rev. 1
Dynamic Self-Calibrating Peak-Detecting Differential Hall Effect Gear Tooth Sensor
Figure 7. The magnetic profile reflects the geometry of the target, allowing the device to present an accurate digital output response.
Target
Mechanical Profile
Target
Magnetic Profile
Sensor Output
Switch State
Sensor Output
Electrical Profile
Target Motion from
Pin 1 to Pin 4
Sensor Output
Electrical Profile
Target Motion from
Pin 4 to Pin 1
The device powers-on in the Off state
V
V
B
OUT
OUT
B+
IN
V+
V+
When the supply voltage, V
On Off On Off On Off On Off
High-pass filtering
The usual dif-
ATS616LSG
CC
,
is below the minimum operating voltage, V
off and stays off, irrespective of the state of the magnetic field.
This prevents false signals, which may be caused by undervolt-
age conditions (especially during power-up), from appearing at
the output.
Output.
sinking up to 20 mA. An external pull-up (resistor) must be sup-
plied to a supply voltage of not more than 24 V.
Output Polarity.
high as the leading edge of a tooth passes the branded face of the
sensor in the direction indicated in figure 6. This means that in
such a configuration, the output voltage will be high when the
sensor is facing a tooth. If the target rotation is in the oppo-
site direction relative to the sensor, the output polarity will be
opposite as well, with the unit switching from low to high as the
leading edge passes the unit.
Figure 6. This left-to-right (pin 1 to pin 4) direction of target rotation
results in a high output signal when a tooth of the target gear is nearest
the branded face of the sensor. A right-to-left (pin 4 to pin 1) rotation
inverts the output signal polarity.
On
The device output is an open-collector stage capable of
Rotating Target
Signature Tooth
The output of the unit will switch from low to
Off
On Off
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
On Off
1
4
CC(UV)
On Off
, the device is
Branded Face
of Sensor
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