A1360 Datasheet, PDF (16/25 Pages) Allegro MicroSystems – Low-Noise Programmable Linear Hall Effect Sensor ICs with

A1360, A1361, Low-Noise Programmable Linear Hall Effect Sensor ICs with
and A1362
Adjustable Bandwidth (50 kHz Maximum) and Analog Output
Programming Procedures
Parameter Selection
Each of the four programmable parameters can be accessed
through its corresponding parameter register. These registers are
located in two distinct zones in the A136x devices:
Zone 1, Register 1:
• Fine sensitivity, Sens
Zone 2, Register 1:
• Fine quiescent voltage output, V_OUT(Q)
Zone 2, Register 2:
• Coarse quiescent voltage output, V_OUT(Q)
• Overall device locking, LOCK
To select the register in the first zone, a sequence of one V_PH
pulse, the key for the register, and a second V_PH pulse (with no
VCC supply interruptions) must be applied serially to the VOUT
pin. The pulse train used for selection of the first register, key 1,
is shown in figure 1.
V+
V_P(HIGH)
V_P(MID)
V_P(LOW)
0
t_LOW
t_ACTIVE
Figure 1. Voltage pulse sequence required to select the first
programmable register in the first zone.
After the falling edge of the second V_PH pulse, the bit field of the
selected register may be addressed with the appropriate code (see
Bit Field Addressing section, below).
The first zone must be traversed before the second zone can be
accessed. After completing any bit field addressing in the first
zone, to enter the second zone, apply a third V_PH pulse. As in
the first zone, this must be followed by the key for the parameter
register, then a V_PH pulse and the bit field code (with no VCC
supply interruptions).
Bit Field Addressing
After the register of a programmable parameter has been selected
as described above, the code pulses must be applied serially to
the VOUT pin with no VCC supply interruptions. As each addi-
tional pulse in the code is transmitted, the overall setting of the
bit field increments by 1, up to the maximum possible code for
that register (see the Programming Logic table). The A136x logic
interprets the overall setting (the binary sum of all of the acti-
vated or blown fuses) and applies it to the value of the parameter,
according to the step size for the parameter (shown in the Electri-
cal Characteristics table).
Addressing activates the corresponding fuse locations in the
given bit field by incrementing the binary value of an internal
DAC. Measurements can be taken after each pulse to determine
if the desired result for the programmable parameter has been
reached. Cycling the supply voltage resets all the locations in the
bit field that have unblown fuses to their initial states.
V+
V_P(MID)
V_P(LOW)
0
t_ACTIVE
t_LOW
Figure 2. Bit field addressing pulse train. Addressing the bit field by incre-
menting the code causes the programmable parameter value to change.
The number of bits available for a given programming code, n, varies
among parameters; for example, the bit field for Sensitivity has 8 bits avail-
able, which allows 255 separate codes to be used.
Fuse Blowing
After the required code is found for a given parameter, its value
can be set permanently by blowing individual fuses in the appro-
priate register bit field. Blowing is accomplished by applying a
high voltage pulse, called a blow pulse, of sufficient duration to
permanently set an addressed bit by blowing a fuse internal to the
device. Due to power requirements, the fuse for each bit in the
bit field must be blown individually. To accomplish this, the code
representing the desired parameter value must be translated to a
binary number. For example, as shown in figure 3, decimal code
5 is equivalent to the binary number 101. Therefore bit 2 (code
4) must be addressed and blown, the device power supply cycled,
and then bit 0 (code 1) addressed and blown. The order of blow-
ing bits, however, is not important. Blowing bit 0 first, and then
bit 2, is acceptable.
Allegro MicroSystems, Inc.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com