Description

The A1421, A1422, and A1423 are AC-coupled Hall-effect

sensor ICs which include monolithic integrated circuits that

switch in response to changing differential magnetic fields

created by rotating ring magnets or, when coupled with a

magnet, by ferrous targets. This family of devices also includes

an integrated capacitor that provides the high accuracy of analog

sensing without an external filter capacitor. This reduces cost

and components, while improving the reliability of the final

sensor solution.

Magnetic field changes affect the two integrated Hall

transducers and then are differentially amplified on the chip.

Differential design provides immunity to radial vibration,

within the device operating air gap range, by rejection of this

common-mode signal change. Steady-state system offsets

are eliminated using an on-chip differential bandpass filter

with integrated capacitor. This filter also provides relative

immunity to interference from electromagnetic sources. The

device utilizes advanced temperature compensation for the

high-pass filter, sensitivity, and Schmitt trigger switchpoints

to guarantee optimal operation to low frequencies over a wide

range of air gaps and temperatures.

A1421a-DS, Rev. 4

Features and Benefits

• Integrated tracking capacitor

• Used for sensing motion of ring magnet or ferrous targets

• Wide operating temperature range

• Operation with magnetic input signal frequency from

20 Hz to 30 kHz

• EMI/ESD-resistant

• Large effective air gaps

• 4.0 to 26.5 V supply operating range

• Output compatible with CMOS logic families

• Reverse battery protection

• Resistant to mechanical and thermal stress

• Accurate true zero crossing switchpoint (A1421 only)

• High vibration immunity, in running mode (A1423 only)

High Precision Hall Effect AC-Coupled Differential Sensor IC

with Integrated Filter Capacitor

Continued on the next page…

Package: 4 pin SIP (suffix K)

Functional Block Diagram

Not to scale

Hall

Amp

Regulator

Bandpass Filter Integrated

Tracking Capacitor

VOUT

(Pin 2)

VCC

(Pin 1)

GND

(Pin 4)

0.1 uF

V

Diagnostic

Circuitry

Gain

Stage

Dual Hall

Transducers

Comparator

TEST

(Pin 3)

(Required)

V

REF