High Precision Linear Hall-Effect Sensor IC
With an Open Drain Pulse Width Modulated Output
A1356
12
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Overview
Programming is accomplished by sending a series of input volt-
age pulses serially through the VCC pin of the device. A unique
combination of different voltage level pulses controls the internal
programming logic of the device to select a desired programma-
ble parameter and change its value. There are three voltage levels
that must be taken into account when programming. These levels
are referred to as high, V
P(HIGH)
, mid, V
P(MID)
, and low, V
P(LOW)
.
The 1356 features Try mode, Blow mode and Lock mode:
" In Try mode, the value of multiple programmable parameters
may be set and measured simultaneously. The parameter values
are stored temporarily, and reset after cycling the supply volt-
age.
" In Blow mode, the value of a single programmable parameter
may be set and measured, and then permanently set by blowing
solid-state fuses internal to the device. Additional parameters
may be blown sequentially. This mode also is used for blow-
ing the device-level fuse (when Lock mode is enabled), which
permanently blocks the further programming of all parameters.
" Lock mode prevents all future programming of the device. This
is accomplished by blowing a special fuse using Blow 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
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 settings of a particular
register causes its programmable parameter to change, based on
the internal programming logic.
Key A series of mid-level voltage pulses used to select a register,
with a value expressed as the decimal equivalent of the binary
value. The LSB of a register is denoted as key 1, or bit 0.
Code The number used to identify the combination of fuses
activated in a bit field, expressed as the decimal equivalent of the
binary value. The LSB of a bit field is denoted as code 1, or bit 0.
Addressing Increasing the bit field code of a selected register
by serially applying a pulse train through the VCC pin of the
device. Each parameter can be measured during the addressing
process, but the internal fuses must be blown before the program-
ming code (and parameter value) becomes permanent.
Fuse Blowing Applying a high voltage pulse of sufficient
duration to permanently set an addressed bit by blowing a fuse
internal to the device. After a bit (fuse) has been blown, it cannot
be reset.
Blow Pulse A high voltage pulse of sufficient duration to blow
the addressed fuse.
Cycling the Supply Powering-down, and then powering-up the
supply voltage. Cycling the supply is used to clear the program-
ming settings in Try mode.
Programming Guidelines
Programming Pulse Requirements, Protocol at T
A
= 25 癈
Characteristic  Symbol
Notes
Min.  Typ.  Max.  Unit
Programming
Voltage
V
P(LOW)
Measured at the VCC pin.
   5   5.5   V
V
P(MID)
13   15   16   V
V
P(HIGH)
26   27   28   V
Programming
Current
I
P
Minimum supply current required to ensure proper fuse blowing. In addition, a
minimum capacitance, C
BLOW
= 0.1 糉, must be connected between the supply and
GND pins during programming to provide the current necessary for fuse blowing.
The blowing capacitor should be removed and the load capacitance used for properly
programming duty cycle measurements.
300         mA
Pulse Width
t
LOW
Duration of V
P(LOW)
for separating V
P(MID)
and V
P(HIGH)
pulses.
40         約
t
ACTIVE
Duration of V
P(MID)
and V
P(HIGH)
pulses for register selection or bit field addressing.    40         約
t
BLOW
Duration of V
P(HIGH)
pulses for fuse blowing.
40         約
Pulse Rise Time    t
Pr
Rise time required for transitions from V
P(LOW)
to either V
P(MID)
or V
P(HIGH)
.
5      100  約
Pulse Fall Time
t
Pf
Fall time required for transitions from V
P(HIGH)
to either V
P(MID)
or V
P(LOW)
.
5      100  約