A1104 Allegro MicroSystems, A1104 Datasheet - Page 7

• Manufacturer Part Number: A1104
• Description: (A1101 - A1106) Continuous-Time Switch Family
• Manufacturer: Allegro MicroSystems

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A1101, A1102, A1103,
A1104, and A1106
OPERATION
The output of these devices switches low (turns on) when a
magnetic field (south polarity) perpendicular to the Hall sen-
sor exceeds the operate point threshold, B
output is capable of sinking 25 mA and the output voltage is
V
point, B
ence in the magnetic operate and release points is the hysteresis,
B
ing of the output, even in the presence of external mechanical
vibration and electrical noise.
Powering-on the device in the hysteresis region, less than B
higher than B
state is attained after the first excursion beyond B
CONTINUOUS-TIME BENEFITS
Continuous-time devices, such as the A110x family, offer the
fastest available power-on settling time and frequency response.
Due to offsets generated during the IC packaging process,
continuous-time devices typically require programming after
Figure 1. Switching Behavior of Unipolar Switches. On the horizontal axis, the B+ direction indicates increasing south polarity magnetic field
strength, and the B– direction indicates decreasing south polarity field strength (including the case of increasing north polarity). This behavior can
be exhibited when using a circuit such as that shown in Panel B.
hys
OUT(SAT)
, of the device. This built-in hysteresis allows clean switch-
RP
. When the magnetic field is reduced below the release
, the device output goes high (turns off). The differ-
RP
, allows an indeterminate output state. The correct
V+
0
B–
0
B
(A)
HYS
OP
. After turn-on, the
B+
V
V
CC
OUT(SAT)
OP
Functional Description
or B
RP
.
OP
and
Continuous-Time Switch Family
packaging to tighten magnetic parameter distributions. In con-
trast, chopper-stabilized switches employ an offset cancellation
technique on the chip that eliminates these offsets without the
need for after-packaging programming. The tradeoff is a longer
settling time and reduced frequency response as a result of the
chopper-stabilization offset cancellation algorithm.
The choice between continuous-time and chopper-stabilized
designs is solely determined by the application. Battery manage-
ment is an example where continuous-time is often required. In
these applications, V
in order to conserve power (refer to figure 2). The duty cycle
is controlled by the power-on time, t
continuous-time devices have the shorter power-on time, they
are the clear choice for such applications.
For more information on the chopper stabilization technique,
refer to Technical Paper STP 97-10, Monolithic Magnetic Hall
Sensor Using Dynamic Quadrature Offset Cancellation and
Technical Paper STP 99-1, Chopper-Stabilized Amplifiers with a
Track-and-Hold Signal Demodulator.
V
S
CC
is chopped with a very small duty cycle
A110x
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
VCC
GND
(B)
VOUT
PO
, of the device. Because
R
L
Sensor Output
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