ATS627LSG datasheet(17/22 Pages) ALLEGRO

17 / 22 page

True Zero Speed, Low Jitter, High Accuracy

Position Sensor IC

ATS627LSG

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Undervoltage Lockout

When the supply voltage falls below the undervoltage lockout

voltage, VCC(UV), the device enters Reset, where the output

state returns to the Power-On State (POS) until sufficient VCC

is supplied. This lockout feature prevents false signals, caused

by undervoltage conditions, from propagating to the output of

the IC.

Power Supply Protection

The device contains an on-chip regulator and can operate over a

wide VCC range. For devices that must operate from an unregu-

lated power supply, transient protection must be added externally.

For applications using a regulated line, EMI/RFI protection

may still be required. Contact Allegro® for information on the

circuitry needed for compliance with various EMC specifications.

Refer to figure 8 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 speci-

fication). At power-on, the device determines the peak-to-peak

amplitude of the signal generated by the target.

This feature is also active in Running mode, though very conser-

vatively invoked, to optimize the signal amplitude in the scenario

where signal amplitude during the initial calibration period is not

representative of the Running mode signal.

Automatic Offset Adjust (AOA)

The AOA circuitry automatically compensates for the effects of

chip, magnet, and installation offsets. This circuitry is continu-

ously active, including during both Power-on mode and Running

mode, compensating for any offset drift (within the Allowable

User Induced Differential Offset). Continuous operation also

allows it to compensate for offsets induced by temperature varia-

tions over time. This circuitry works with the AGC during cali-

bration to adjust VPROC in the internal range to allow the DACs

to acquire the signal peaks.

Bounded Update

The ATS627 continuously updates its switchpoints based on the

actual signal being received from the target. When the output

switches, the sensor resets the tracking DACs so that each proper

magnetic signal peak can be acquired. To prevent establishing

switchpoints on outlier signal maxima, tracking is limited, or

bounded, in magnitude. If such limiting were not applied, then

anomalous target features, such as bent, broken or misformed

teeth, could create significant output accuracy errors (see fig-

ure 7).

Running Mode Lockout

The ATS627 has a Running mode lockout feature to prevent

switching in response to small amplitude input signals that are

characteristic of vibration signals. The internal logic of the chip

interprets small signal amplitudes below a certain level to be the

result of target vibration. The output is held to the state present

prior to lockout, until the amplitude of the signal returns to nor-

mal operational levels.

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