A119 Datasheet, PDF (12/22 Pages) Allegro MicroSystems – Programmable, Chopper-Stabilized, Two-Wire Hall-Effect Switches

A119x and A119x-F
Programmable, Chopper-Stabilized,
Two-Wire Hall-Effect Switches
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-
ming. These levels are referred to as high (V_PH), mid (V_PM), and
low (V_PL) (see figure 1 and table 1).
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 through your local Allegro sales repre-
sentative. The manual for the kit provides additional information
on programming these devices, and is available for download on
the Allegro MicroSystems website.
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.
Key. A series of V_PM voltage pulses used to select a register or mode.
t_ACTIVE
V_PH
t_Pr
t_Pf
t_BLOW
V_PM
V_PL
(Supply
cycled)
0
t_LOW
Programming Blow
pulses
pulse
t_LOW
Figure 4. Programming pulse definition (see table 1)
Table 1. Programming Pulse Requirements, Protocol at T_A = 25°C (refer also to figure 4)
Characteristic Symbol
Notes
V_PL
Programming Voltage
V_PM
Measured at the VCC pin.
V_PH
t_Pr = 11 µs, V_CC = 5 → 26 V, C_BLOW = 0.1 µF (min). Minimum supply current
Programming Current
I_PP
required to ensure proper fuse blowing. C_BLOW must be connected between the
VCC and GND pins during programming to provide the current necessary for fuse
blowing.
Pulse Width
Pulse Rise Time
Pulse Fall Time
Blow Pulse Slew Rate
t_LOW
t_ACTIVE
t_BLOW
t_Pr
t_Pf
SR_BLOW
Duration at V_PL separating pulses at V_PM or V_PH.
Duration of pulses at V_PM or V_PH for key/code selection.
Duration of pulse at V_PH for fuse blowing.
V_PL to V_PM , or V_PL to V_PH.
V_PH to V_PL , or V_PM to V_PL.
Min. Typ. Max. Unit
4.5 5 5.5 V
12.5 – 14 V
21 – 27 V
175 –
– mA
20 –
– µs
20 –
– µs
90 100 – µs
5
– 100 µs
5
– 100 µs
375 –
– mV/ µs
Allegro MicroSystems, LLC
12
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com