High Precision Hall Effect AC-Coupled Differential

Sensor IC with Integrated Filter Capacitor

A1421, A1422,

and

A1423

13

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

On

Off

1421 Switching State

Applied Magnetic

B

0.0

15.0

–15.0

OP(typ)1421, 1422

Off

Off

On

On

1422 Switching State

Off

On

On

1423 Switching State

t+

65.0

–65.0

Figure 2. Comparative typical output characteristics. This chart illustrates the switchpoints and the output polarities of the A1421,

A1422, and the A 1423. Characteristics shown without delay, see characteristic data charts for delay and phase shift contributions.

in the Characteristic Data section quantify the effect of the input

signal amplitude on the phase shift of the output. Positive values

of delay indicate a lagging output, while negative values indicate

a leading output.

AC-Coupled Operation

Steady-state magnet and system offsets are eliminated using an

on-chip differential bandpass filter. The upper and lower cut-off

frequencies of this patented filter are set using an internal inte-

grated capacitor. The differential structure of this filter improves

the ability of the IC to reject single-ended noise on the GND

or VCC lines and, as a result, makes the device more resistant

to EMI (electromagnetic interference) typically seen in hostile

remote-sensing environments.

Power Supply Protection

The device contains an on-chip voltage regulator and can operate

over a wide supply voltage range. In applications that operate the

device from an unregulated power supply, transient protection

must be added externally. For applications using a regulated line,

EMI/RFI protection may still be required. The circuit shown

in figure 3 is the most basic configuration required for proper

device operation.

Typical Circuit

put terminals, as shown in figure 3. Also, the auxilliary terminal,

TEST, must be connected externally to the GND terminal.

2

1

3

4

V

OUT

0.1 uF

R

PU

V

S

VCC

TEST

VOUT

GND

A1421, A1422

or A1423

Figure 3. Basic application circuit

with the output driver.