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PDF A1425 Data sheet ( Hoja de datos )
| Número de pieza | A1425 | |
| Descripción | High Accuracy Analog Speed Sensor IC | |
| Fabricantes | Allegro MicroSystems | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de A1425 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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A1425
High Accuracy Analog Speed Sensor IC with Integrated Filter
Capacitor and Dual Zero-Crossing Output Signal
Features and Benefits
▪ Used in sensing motion of ring magnet or ferrous targets
▪ Integrated filter capacitor
▪ Wide operating temperature range
▪ Operation with magnetic input signal frequency from
20 Hz to 20 kHz
▪ Resistant to EMI
▪ Large effective air gaps
▪ 4.0 to 26.5 V supply operating range
▪ Output compatible with both TTL and CMOS logic
families
▪ Reverse battery protection
▪ Resistant to mechanical and thermal stress
▪ Accurate true zero-crossing switchpoint
Package: 4 pin SIP (suffix K)
Description
The A1425 AC-coupled Hall-effect sensor IC is a monolithic
integrated circuit that switches in response to changing
differential magnetic fields created by rotating ring magnets
and, when coupled with a magnet, by ferrous targets.The device
is a true zero-crossing detector: the output switches precisely
when the difference in magnetic field strength between the
two Hall elements is zero. A unique dual-comparator scheme
provides for accurate switching at the zero crossing on both the
positive and negative-going regions of the differential signal,
while utilizing hysteresis to prevent false switching. The zero-
crossing nature of this device provides excellent repeatability
and accuracy for crankshaft applications.
Changes in field strength at the device face, which are
induced by a moving target, are sensed by the two integrated
Hall transducers. The transducers generate signals that are
differentially amplified by on-chip electronics.This differential
design provides immunity to radial vibration within the
operating air gap range of the A1425, by rejection of the
common mode signal. Steady-state magnet and system offsets
are eliminated using an on-chip differential band-pass filter.
This filter also provides relative immunity to interference from
electromagnetic sources.
Continued on the next page…
VS+
VCC
(Pin 1)
Functional Block Diagram
Dual Hall
Transducers
Regulator
0.1 uF
Hall
Amp
Gain
Stage
Bandpass Filter Integrated
Tracking Capacitor
VREF
Diagnostic
Circuitry
Comparator
TEST
(Pin 3)
VOUT
(Pin 2)
1425-DSa, Rev.3
GND
(Pin 4)
(Required)
1 page  
A1425
High Accuracy Analog Speed Sensor IC with Integrated
Filter Capacitor and Dual Zero-Crossing Output Signal
Empirical Results
Supply Current by Ambient Temperature
7
6
5
4
3
2
1
0
–50 0
VCC (V)
4.5
1122.0
2260.0
50 100 150 200
TA (ºC)
Supply Current by Supply Voltage
7
6
TA (ºC)
150
5
25
–40
4
3
2
1
0
0 10 20 30
VCC (V)
Output Voltage by Ambient Temperature
ISINK = 20 mA
500
450 VCC (V)
400
350
4.5
12.0
20.0
300
250
200
150
100
50
0
–50 0
50 100 150 200
TA (ºC)
500
450
400
350
300
250
200
150
100
50
0
0
Output Voltage by Supply Voltage
ISINK = 20 mA
TA (ºC)
150
25
–40
5 10 15 20 25
VCC (V)
Continued on next page.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
5 Page 
A1425
High Accuracy Analog Speed Sensor IC with Integrated
Filter Capacitor and Dual Zero-Crossing Output Signal
Applications Information
Target Selection
The zero-crossing switchpoints and AC-coupled operation of this
device make target selection important. For high-density target
geometries or small target features that produce a sinusoidal
magnetic signal, the high-pass filter is capable of filtering offsets
that may be induced in the final device output. If such offset is
present, and the target has larger features, then the high-pass
filter may not be effective at higher speeds and an accuracy shift
may occur. These relationships are shown in figure 2.
Power Supply Protection
The A1425 contains an on-chip voltage regulator and can oper-
ate over a wide supply voltage range. In applications that operate
the device from an unregulated power supply, transient protec-
tion must be added externally. For applications using a regulated
line, EMI/RFI protection may still be required. The circuit
shown in figure 3 is the most basic configuration required for
proper device operation.
Large Feature (Tooth)
Valley
+B
(a)
0
–B
+V
0.1 uF
4
1
A1425
2
VCC
RPU
VOUT
3
0 (Required)
t
Output Edge
+B
Shift
(b)
0
Figure 3. Basic application circuit. A pull-up resistor, RPU, is required
with the output driver.
–B
+V
0
t
Figure 2. Large Feature Effects. (a) Large target feature but no device offset,
normal edge position. (b) Large target feature with negative device offset, shifted
(advanced) output edge position.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet A1425.PDF ] | |
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