Description

The A1642 is an optimized Hall effect sensing integrated

circuit that provides a user-friendly solution for true zero-speed

digital ring-magnet sensing in two-wire applications.This small

package can be easily assembled and used in conjunction with

a wide variety of target shapes and sizes.

The integrated circuit incorporates dual Hall effect elements

and signal processing that switches in response to differential

magnetic signals created by ring magnet poles. The circuitry

contains a sophisticated digital circuit to reduce system offsets,

to calibrate the gain for air-gap–independent switchpoints,

and to achieve true zero-speed operation. Signal optimization

occurs at power-on through the combination of offset and

gain adjust and is maintained throughout the operating time

with the use of a running-mode calibration. The running-mode

calibration allows immunity to environmental effects such as

micro-oscillations of the target or sudden air gap changes.

The regulated current output is configured for two-wire

applications and the A1642 is ideally suited for obtaining

speed and duty cycle information in ABS (antilock braking

systems). The 1.5 mm spacing between the dual Hall elements

is optimized for fine pitch ring-magnet–based configurations.

For applications requiring sensing of rotating ferrous gears and

targets, refer to theAllegroATS series of products.The package

is lead (Pb) free, with 100% matte tin leadframe plating.

A1642LKN-DS, Rev. 4

Features and Benefits

▪ Running mode calibration for continuous optimization

▪ Single chip IC for high reliability

▪ Internal current regulator for 2-wire operation

▪ Precise duty cycle signal over operating temperature range

▪ Large operating air gaps

▪ Automatic Gain Control (AGC) for air gap independent

switchpoints

▪ Automatic Offset Adjustment (AOA) for signal processing

optimization

▪ True zero-speed operation

▪ Undervoltage lockout

▪ Wide operating voltage range

▪ Wide-lead package suitable for welding external

components directly to the package leads or for welding

the device to a leadframe.

Two-Wire True Zero-Speed Miniature Differential

Peak-Detecting Sensor IC with Continuous Calibration

Package: 4-pin SIP (Suffix KN)

Functional Block Diagram

Not to scale

A1642

VCC

Automatic Offset

Control

AOA DAC

Hall

Amplifier

AGC DAC

Gain

Tracking

DAC

Peak Hold

Gain Control

Internal Regulator

Test Signals

GND

Test