A1425 Allegro MicroSystems, A1425 Datasheet

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A1425

Manufacturer Part Number
A1425
Description
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
Manufacturer
Allegro MicroSystems
Datasheet

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High Accuracy Analog Speed Sensor with Integrated Filter Capacitor
A1425-DS Rev. 0b
Supply Voltage, V
Reverse-Supply Voltage, V
Output Current, I
Reverse-Output Current, I
Reverse-Output Voltage, V
Operating Temperature
Storage Temperature, T
Preliminary Data Sheet
Subject to Change Without Notice
November 10, 2004
Ambient, T
Maximum Junction, T
AB SO LUTE MAX I MUM RAT INGS
1. VCC
2. VOUT
3. Test pin, tie to GND
4. GND
Package K, 4-pin SIP
A
................................ –40ºC to 150ºC
1
OUT
CC
.......................................... 28 V
.......................................25 mA
2
S
.................. –65ºC to 170ºC
3
J(max)
ROUT
ROUT
RCC
4
........................ –18 V
.....................–50 mA
........................165ºC
...................–50 mA
The A1425 ac-coupled Hall-effect sensor is a monolithic integrated circuit that
switches in response to changing differential magnetic fi elds created by rotating
ring magnets or, 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 fi eld strength between the two Hall elements is zero. A unique dual-
comparator scheme provides for accurate switching during zero-crossing, both
when the sensed fi eld is increasing in strength and when it is decreasing, while
utilizing hysteresis to prevent false switching. The zero-crossing nature of this
device provides excellent repeatability for crankshaft applications.
Changes in fi eld strength at the device face caused by a moving target are sensed
by the two integrated Hall transducers, generating signals that are differen-
tially amplifi ed by on-chip electronics. This differential sensing 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 fi lter. This fi lter also provides
relative immunity to interference from electromagnetic sources.
The device utilizes advanced temperature compensation for the high-pass fi lter,
sensitivity, and the Schmitt trigger switchpoints, guaranteeing optimal operation to
low frequencies over a wide range of air gaps and temperatures.
Each Hall effect digital integrated circuit includes a voltage regulator, two Hall
effect sensing elements, temperature compensating circuitry, a low-level ampli-
fi er, band-pass fi lter, Schmitt trigger, and an output driver. The on-board regulator
permits operation with supply voltages from 4.0 to 26.5 V. The output stage can
easily switch 20 mA over the full frequency response range of the sensor, and is
compatible with both TTL and CMOS logic circuits.
The device is packaged in a 4-pin plastic SIP (part number suffi x -K).
Features and Benefi ts
Use the following complete part number when ordering:
• Senses motion of ring magnet targets
• Integrated fi lter capacitor
• Wide operating temperature range
• Operation with frequency of sensed transitions from 20 Hz to 30 kHz
• EMI-resistant
• Large working air gaps
• 4.0 to 26.5 V operating range
• Output compatible with both TTL and CMOS logic families
• Reverse battery protection
Engineering samples available on a limited basis. Contact your local
A1425
and Dual Zero-Crossing Output Signal
Part Number
sales or applications support offi ce for additional information.
A1425LK
4-pin plastic SIP
Package
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Ambient (ºC)
–40 to 150

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A1425 Summary of contents

Page 1

... Hall transducers, generating signals that are differen- tially amplifi on-chip electronics. This differential sensing 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 fi ...

Page 2

... Without Notice November 10, 2004 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal V+ VCC (Pin 1) Dual Hall Elements Hall 0.1 uF Amp A1425-DS Rev. 0b A1425 Functional Block Diagram Regulator Bandpass Filter Integrated Tracking Capacitor Gain Stage Test Pin (Pin 3) ...

Page 3

... Output Rise Time will be dominated by the RC time constant. 5 For other sinusoidal signal frequencies and magnetic fi elds, –B Data section. 6 See Defi nitions of Terms section. 7 Exceeding the maximum magnetic fi eld may result in compromised absolute accuracy. A1425-DS Rev. 0b A1425 Valid – 40 º 150 º ≤ ...

Page 4

... This value may be greater than or less than 0 G. Output On Switchpoint (Release Point), B decreasing differential magnetic fl ux density at which the device A1425-DS Rev. 0b A1425 may require derating at maximum conditions, see application information Symbol Test Conditions ...

Page 5

... Ambient Temperature OUT(SAT) Over V Range 500 450 400 350 300 250 200 150 100 50 0 – Ambient Temperature, T Continued on next page. A1425-DS Rev. 0b A1425 Empirical Results Range V (V) CC 4.5 12.0 20.0 100 150 200 (º Range V (V) CC 4.5 12 ...

Page 6

... Preliminary - Subject to Change Without Notice November 10, 2004 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal A1425-DS Rev. 0b A1425 Empirical Results, continued Air Gap (mm) Air Gap (mm) 6 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 ...

Page 7

... Continued on next page. A1425-DS Rev. 0b A1425 Simulation Results by Frequency of Sensed Transitions diff Over the Range of Ambient Operating Temperatures, T 0.1 1 Frequency, f (kHz) Bdiff Typical Phase Shifts, by Frequency of Sensed Transitions Over the Range of Applied Magnetic Fields, B ...

Page 8

... Typical Output Signal Delay by Frequency of Sensed Transitions 100 Hz 1000 0 –1000 –2000 –3000 –4000 –5000 –6000 0 A1425-DS Rev. 0b A1425 Simulation Results, continued Typical Output Signal Delay by Frequency of Sensed Transitions, >100 Hz Over the Range of Applied Magnetic Fields Frequency, f (kHz) Bdiff Over the Range of Applied Magnetic Fields, B ...

Page 9

... Bulk Current Injection TEM Cell * ESD test is done with no external components. Recommended EMC test circuit. Test circuit recommended confi guration may change after evaluation of fi rst silicon. A1425-DS Rev. 0b A1425 Sensor Evaluation: EMC Characterization Test Name Reference Specifi cation * ...

Page 10

... B HYS2 Off On , the output signal OUT diff will be valid for B > 50 Gp-p, OUT diff , has also elapsed circuit in the A1425 is briefl y enabled that PO . Simulation diff OP(max) RP(max OP(min) RP(min) Off Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www ...

Page 11

... 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 fi ...

Page 12

... Preliminary - Subject to Change Without Notice November 10, 2004 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal A1425-DS Rev. 0b A1425 Package K, 4-pin SIP The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283; ...

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