Programming Guidelines

Overview

Programming is accomplished by sending a series of input volt-

age pulses serially through the VCC (supply) pin of the device.

A unique combination of different voltage level pulses controls

the internal programming logic of the device to select a desired

programmable parameter and change its value. There are three

voltage levels that must be taken into account when program-

The A119x family features two programmable modes, Try mode

and Blow mode.

• In Try mode, programmable parameter values are set and mea-

sured. A parameter value is stored temporarily, and reset after

cycling the supply voltage.

• In Blow mode, the value of a programmable parameter may

be permanently set by blowing solid-state fuses internal to the

device. Device locking is also accomplished in this mode.

The programming sequence is designed to help prevent the

device from being programmed accidentally; for example, as a

result of noise on the supply line. Although any programmable

variable power supply can be used to generate the pulse wave-

forms, Allegro highly recommends using the Allegro Sensor IC

Evaluation Kit, available on the Allegro website On-line Store.

The manual for that kit is available for download free of charge,

and provides additional information on programming these

devices.

Definition of Terms

Register. The section of the programming logic that controls the

choice of programmable modes and parameters.

Bit Field. The internal fuses unique to each register, represented

as a binary number. Changing the bit field selection in a particu-

lar register causes its programmable parameter to change, based

on the internal programming logic.

Characteristic

Symbol

Notes

Min. Typ. Max. Unit

Programming Voltage

Measured at the VCC pin.

4.5

5

5.5

V

12.5

–

14

V

21

–

27

V

Programming Current

VCC and GND pins during programming to provide the current necessary for fuse

blowing.

175

–

–

mA

Pulse Width

–

–

μs

20

–

–

μs

90

100

–

μs

Pulse Rise Time

5

–

100

μs

Pulse Fall Time

5

–

100

μs

Blow Pulse Slew Rate

375

–

–

mV/ μs

0

(Supply

cycled)

Programming

pulses

Blow

pulse

Figure 4. Programming pulse definition (see table 1)

Programmable, Chopper-Stabilized,

Two Wire Hall-Effect Switches

A1190, A1192,

and A1193

9

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com