a1181 Allegro MicroSystems, Inc., a1181 Datasheet - Page 8

• Manufacturer Part Number: a1181
• Description: Two-wire, Programmable, Chopper-stabilized, Unipolar Hall-effect Switch Microsystems
• Manufacturer: Allegro MicroSystems, Inc.

Applications. It is necessary that an external bypass capacitor be connected between the supply and ground of the
device to reduce both external noise and noise generated by the chopper-stabilization technique and ensure sufficient
energy to guarantee proper programming. (A 0.1uF cap is recommended for proper fuse blowing and may reside on the
programming board) The bypass capacitor in the application should be no further than 5 mm away from the Hall sensor.
The bypass capacitor is to protect the Hall IC only. All high frequency interferences conducted along the supply lines will
be passed directly to the load through the bypass capacitor. Therefore, the ECU must have sufficient protection other
than the bypass capacitor placed in parallel with the Hall IC.
A series resistor on the supply side, Rs (not shown), in combination with the bypass capacitor will create a filter for EMC
pulses. The series resistor (Rs) and/or sense resistor (Rsense) will have voltage drops across them that must be
considered for the minimum Vcc requirement of the device. The preferred sense resistor value is approximately 100
ohms. All programming, code and lock-bit programming, should be done directly across the part, between V
Output with the use of a 0.1uF bypass capacitor. Programming across the series resistor or sense resistor may not allow
enough energy to properly blow the fuses. The result would be incorrect switch points.
Typical Application (UA Pkg):
Extensive applications information on magnets and Hall-effect sensors including Chopper-Stabilization is available in the
Allegro Electronic Data Book CD, or at the website:
TWO-WIRE, PROGRAMMABLE, UNIPOLAR HALL-EFFECT SWITCH FAMILY
Rev. 1.8 25 April 2003
V
Supply
Page 8
(PRELIMINARY INFORMATION – SUBJECT TO CHANGE)
TYPICAL APPLICATION CIRCUIT
http://www.allegromicro.com
Optional OUTPUT
A118X
UA ONLY
3
Vcc
1
OUTPUT
2
0.01uF
.
115 Northeast Cutoff, Box 15036
Worcester, Massachus etts 01615-0036 [phone]
Copyright © 1993, 1995 Allegro MicroSystems, Inc.
R
SENSE
ECU
CC
and