High Precision, Output Pin Programmable
Linear Hall Effect Sensor ICs
A1373 and
A1374
15
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Several parameters can be field-programmed. To do so, a coded
series of voltage pulses through the VOUT pin is used to set
bitfields in onboard registers. The effect on the device output can
be monitored, and the registers can be cleared and set repeatedly
until the required output results are achieved. To make the setting
permanent, bitfield-level solid state fuses are blown, and finally,
a device-level fuse is blown, blocking any further coding.
Although any programmable variable power supply can be
used to generate the pulsed waveforms, Allegro highly recom-
mends using the Allegro Sensor IC Evaluation Kit, available on
the Allegro Web site On-line Store. The manual for that kit is
available for download free of charge, and provides additional
information on programming these devices.
There are three voltage levels that must be taken into account
when programming. For purposes of explanation in this docu-
ment, the signal levels are referred to simply as high program-
ming voltage, V
PH
, mid, V
PM
, and low, V
PL
.
The rising edge of the high level, V
PH
, pulse generates a state
change. The falling edge of the high level, V
PH
, pulse increments
the mode, register, or bitfield selection by one, when allowed to
drop below the low level, V
PL
, threshold. A delay on the fall-
ing edge, at the mid level, V
PM
, range is required to guarantee
proper programming level recognition. When it is not desirable to
increment these fields further, it is acceptable to hold the signal
at the mid level, V
PM
, range and then transition to another high
level, V
PH
, pulse. Referring to the Programming State Machine
diagram, when using Blow Fuse mode the fourth high level, V
PH
,
pulse (including the key sequence to enable Blow Fuse mode),
will blow the selected key-code combination. If fuse blowing is
not desired, it is recommended to reset the A137x by toggling the
supply pin. If the high level, V
PH
, pulse is not generated, and the
A137x is not reset, then the next key sequence to change states
will blow the unwanted key-code combination. For multiple
register addressing without fuse blowing, Try Value mode must
be used.
Pulse Generation
PROGRAMMING PROTOCOL CHARACTERISTICS, over operating temperature range, unless otherwise noted
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Programming Voltage
1
V
PL
Low voltage range, for addressing registers and
bitfields
0–5V
V
PM
Mid voltage range, for addressing bitfields and for
separating programming signals
14 – 16 V
V
PH
High voltage range, for enabling state changes
and for fuse blowing
25 26 27 V
Programming Current
2
I
PP
t
r
= 11 s; 5 V 28 V; C
PROG
= 0.1 F – 209 – mA
Pulse Width
t
PHE
High pulse duration for enabling state change 20 – – s
t
PHP
High pulse duration for blowing fuses 100 – – s
t
PLA
Low pulse duration for bitfield addressing 6 – – s
t
PME
Mid pulse delay on falling edge of high pulse, V
PH
15 – – s
t
PMA
Mid pulse duration for bitfield addressing 6 – – s
Pulse Rise Time t
r
V
PL
to V
PH
or V
PM
; maximum may be application
dependent
5 – 100 s
Pulse Fall Time t
f
V
PH
or V
PM
to V
PL
; maximum may be application
dependent
5 – 100 s
1
Programming voltages are measured at pin #3, VOUT, of the A137x.
2
A minimum capacitance of 0.1 F must be connected from VOUT to the GND pin of the A137x in order to provide the current
necessary to blow the fuse.
