13

ATS643-DS, Rev. 1

Worcester, Massachusetts 01615-0036 (508) 853-5000

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

Self-Calibrating, Zero-Speed Differential GTS with Continuous Update

ATS643LSH

Undervoltage Lockout. When the supply voltage falls

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

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.

2

ATS643

1

3

4

VCC

0.01 µF

100 Ω

(Optional)

(Optional)

Figure 7. Typical basic circuit for proper device operation.

Mechanical Profile

Internal Differential

Analog Signal

Response, with AGC

Internal Differential

Analog Signal

Response, without AGC

Ferrous Target

V+

V+

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.