True Zero-Speed, High Accuracy Gear Tooth Sensor IC

ATS667LSG

11

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

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

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 6 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. The gain of the IC

is then automatically adjusted. Figure 7 illustrates the effect of

this feature.

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.

Running Mode Lockout

The ATS667 has a running mode lockout feature to prevent

switching in response to small signals that are characteristic of

vibration signals. The internal logic of the chip considers small

signal amplitudes below a certain level to be vibration. The out-

put is held to the state prior to lockout until the amplitude of the

signal returns to normal operational levels.

Assembly Description

The ATS667 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.

Figure 6. Typical circuit for proper device operation.

Figure 7. 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, as shown in the lowest panel.

Mechanical Profile

Internal Differential

Analog Signal

Response, with AGC

Internal Differential

Analog Signal

Response, without AGC

Ferrous Target

V+

V+

43

VCC

GND TEST

VOUT

0.1 μF

(Required)

ATS667

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