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A1381 Datasheet(PDF) 12 Page - Allegro MicroSystems

Part No. A1381
Description  Programmable Linear Hall Effect Sensor ICs with Analog Output
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Maker  ALLEGRO [Allegro MicroSystems]
Homepage  http://www.allegromicro.com
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A1381 Datasheet(HTML) 12 Page - Allegro MicroSystems

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Programmable Linear Hall Effect Sensor ICs with Analog Output
Available in a Miniature Thin Profile Surface Mount Package
A1381, A1382,
A1383, and A1384
12
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Figure 1. Parameter selection pulse train. This shows the sequence for
selecting the register corresponding to key 1, indicated by a single VPM
pulse.
Parameter Selection
Each programmable parameter can be accessed through a specific
register. To select a register, a sequence of voltage pulses con-
sisting of a VPH pulse, a series of VPM pulses, and a VPH pulse
(with no VCC supply interruptions) must be applied serially to
the VOUT pin. The number of VPM pulses is called the key, and
uniquely identifies each register. The pulse train used for selec-
tion of the first register, key 1, is shown in figure 1.
The A138x has three registers that select among the five pro-
grammable parameters:
Register 1:
Quiescent voltage output, VOUT(Q)
Register 2:
Sensitivity, Sens
Register 3:
Sensitivity temperature coefficient, TCSens
Polarity, POL
Overall device locking, LOCK
Bit Field Addressing
After a programmable parameter has been selected, a VPH pulse
transitions the programming logic into the bit field address-
ing state. Applying a series of VPM pulses to the VOUT pin of
the device, as shown in figure 2, increments the bit field of the
selected parameter.
When addressing the bit field, the number of VPM pulses is rep-
resented by a decimal number called a code. Addressing activates
the corresponding fuse locations in the given bit field by incre-
menting the binary value of an internal DAC. The value of the bit
field (and code) increments by one with the falling edge of each
VPM pulse, up to the maximum possible code (see the Program-
ming Logic table). As the value of the bit field code increases, the
value of the programmable parameter changes.
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.
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 VPH pulse, called a blow pulse, of sufficient duration at the
VP(HIGH) level 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 accom-
plish this, the code representing the desired parameter value must
be translated to a binary number. For example, as shown
V+
0
VP(HIGH)
VP(MID)
VP(LOW)
V+
0
tLOW
tACTIVE
VP(HIGH)
VP(MID)
VP(LOW)
Figure 2. Bit field addressing pulse train. Addressing the bit field by
incrementing 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 VOUT(Q) has 6 bits
available, which allows 63 separate codes to be used.
Programming Procedures


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