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Part: A1425LK
Category:
Description: High Precision Hall Effect Ac-coupled Differential Sensor With Integrated Filter Capacitor
Company: Allegro Micro Systems, Inc.
Datasheet: Download A1425LK datasheet File size : 89 kB
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Preliminary Data Sheet Subject to Change Without Notice June 16, 2004
A1425
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
The A1425 ac-coupled Hall-effect sensor is a monolithic integrated circuit that switches in response to changing differential magnetic fields 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 field strength between the two Hall elements is zero. A unique dualcomparator scheme provides for accurate switching during zero-crossing, both when the sensed field 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 field strength at the device face caused by a moving target are sensed by the two integrated Hall transducers, generating signals that are differentially amplified 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 filter. This filter also provides relative immunity to interference from electromagnetic sources. The device utilizes advanced temperature compensation for the high-pass filter, 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 amplifier, band-pass filter, 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 suffix -K).
Package K, 4-pin SIP
1
2
3
4
1. VCC 2. VOUT 3. Test pin, tie to GND 4. GND
Features and Benefits
· · · · · · · · · Senses motion of ring magnet targets Integrated filter 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
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC ......... 28 V Reverse-Supply Voltage, VRCC ...... 18 V Output Current, IOUT ...... 25 mA Reverse-Output Current, IROUT............ 50 mA Reverse-Output Voltage, VROUT ..........50 mA Operating Temperature Ambient, TA........ 40ºC to 150ºC Maximum Junction, TJ(max)......165ºC Storage Temperature, TS ......... 65ºC to 170ºC
Use the following complete part number when ordering:
Part Number A1425LK Package 4-pin plastic SIP Ambient (ºC) 40 to 150
Engineering samples available on a limited basis. Contact your local sales or applications support office for additional information.
A1425-DS Rev. 0a
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
Preliminary - Subject to Change Without Notice June 16, 2004
A1425
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
Functional Block Diagram
V+ VCC (Pin 1) Test Pin (Pin 3)
Regulator Dual Hall Elements Dual Comparators
Diagnostic Circuitry
Bandpass Filter Integrated Tracking Capacitor Hall Amp Gain Stage
VOUT (Pin 2)
0.1 uF
Logic
GND (Pin 4)
A1425-DS Rev. 0a
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
2
Preliminary - Subject to Change Without Notice June 16, 2004
A1425
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
OPERATING CHARACTERISTICS Valid at TA = 40ºC to 150ºC, TJ 165°C; over operational air gap range and VCC within operating range, unless otherwise noted. Typical operating parameters: VCC = 12 V and TA = 25°C.
Characteristic ELECTRICAL CHARACTERISTICS Supply Voltage Supply Current Output Saturation Voltage Output Leakage Current VCC ICC VOUT(SAT) ISINK = 20 mA IOFF VOUT = 24 V, Bdiff = 0 Operating; TJ < TJ(max) 4.0 4.2 140 26.5 7.0 400 5 V mA mV µA Symbol Test Conditions Min. Typ. Max. Units
PROTECTION COMPONENT CHARACTERISTICS Reverse Supply Current Supply Zener Current Supply Zener Clamp Voltage Output Zener Current Output Zener Clamp Voltage Output Short Circuit Current Limit RESPONSE CHARACTERISTICS Power-On Time2,6 Settling Time3,6 Response Time6 Upper Corner Frequency Lower Corner Frequency OUTPUT CHARACTERISTICS Output Rise Time4 Output Fall Time MAGNETIC CHARACTERISTICS Output Off Switchpoint5,6 Output On Switchpoint5,6 Applied Magnetic Field6,7
1Equivalent to I
IRCC IZCC VZCC IZOUT VZOUT IOUT(lim)
VCC = 18 V VCC = 28 V ICC = 10 mA1, TA = 25°C VOUT = 28 V IOUT = 3 mA, TA = 25°C
28 28
33
1 10 37 3 50
mA mA V mA V mA
tPO tS tR fcu fcl tr tf BOP BRP Bdiff
VCC > VCC(min) fBdiff 100 Hz Equal to tPO + tS; fBdiff 100 Hz 3 dB, single pole 3 dB, single pole RPU = 1 k, C = 10 pF RPU = 1 k, ISINK = 20 mA, C = 10 pF Bdiff increasing, fBdiff = 200 Hz, Bdiff = 50 Gp-p; digital output signal switches low to high Bdiff decreasing, fBdiff = 200 Hz, Bdiff = 50 Gp-p; digital output signal switches high to low Differential p-p magnetic field
0 4.5 30
4.5
9 50 59 20 200 200
ms ms ms kHz Hz ns ns
11 11 50
0 0
11 11 1250
G G G
CC(max) + 3 mA. 2Time required to initialize device. 3Time required for the output switchpoints to be within specification. 4Output Rise Time will be dominated by the RC time constant. 5For other sinusoidal signal frequencies and magnetic fields, B OP = BRP = sin(Bdiff / 2) ± 25%, where is the phase shift shown in the Characteristic Data section. 6 See Definitions of Terms section. 7 Exceeding the maximum magnetic field may result in compromised absolute accuracy.
A1425-DS Rev. 0a
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
3
Preliminary - Subject to Change Without Notice June 16, 2004
A1425
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Package Thermal Resistance Symbol RJA Test Conditions Minimum-K PCB (single-sided with copper limited to solder pads) Min. 177 Typ. Max Units ºC/W
30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 20 40
Power Derating Curve T J(max) = 1 6 5 º C ; I CC = ICC(max)
VCC(max)
900 850 800 750 700 650 600 550 500 450 400 350 300 250 200 150 100 50 0 20
M a x i m u m P o w e r D i s s i p a t i o n , PD(max) TJ(max) = 165ºC; VCC = VCC(max); ICC = ICC(max)
Maximum Allowable V CC (V)
Power Dis s ipation, PD (m W)
M (R inim
J A
Minimum-K PCB ( R JA = 1 7 7 º C / W )
u = m-K 17 P 7C ºC B /W )
VCC(min)
60
80
100
120
140
160
180
40
60
80 100 120 Temperature (°C)
140
160
180
Definitions of Terms The following provide additional information about some of the parameters cited in the Operating Characteristics table. For additional information, visit the Allegro Web site at www.allegromicro.com. Applied Magnetic Field, Bdiff The differential magnetic flux density which is calculated as the arithmetic difference of the flux densities observed by each of the two Hall elements. Output Off Switchpoint (Operate Point), BOP The value of increasing differential magnetic flux density at which the device output switches from low to high. This value may be greater than or less than 0 G. Output On Switchpoint (Release Point), BRP The value of decreasing differential magnetic flux density at which the device output switches from high to low. This value may be greater than or less than 0 G. Power-On Time, tPO The time needed by the device, after power is applied, to initialize all circuitry necessary for proper operation. Settling Time, tS The time required by the device, after tPO, and after a valid magnetic signal has been applied, to provide proper output transitions. Settling time is a function of magnetic offset, offset polarity, signal phase, signal frequency, and signal amplitude. Response Time The total time required for generating zerocrossing output transitions after power-up (the sum of power-on time and settling time).
A1425-DS Rev. 0a
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
4
Preliminary - Subject to Change Without Notice June 16, 2004
A1425
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
Empirical Results
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 50
Over VCC Range
VCC (V)
4.5 12.0 20.0
ICC(OFF) by TA
ICC(OFF) by VCC
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 Over TA Range
TA (ºC)
150 25 40
Current (mA)
0
50
100
150
200
Current (mA)
0
5
10
15
20
25
Ambient Temperature, TA (ºC)
Supply Voltage, VCC (V)
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 50
Over VCC Range
VCC (V)
4.5 12.0 20.0
ICC(ON) by TA
ICC(ON) by VCC
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 Over TA Range
TA (ºC)
150 25 40
Current (mA)
Current (mA)
0
50
100
150
200
0
5
10
15
20
25
Ambient Temperature, TA (ºC)
Supply Voltage, VCC (V)
500 450 400 350 300 250 200 150 100 50 0 50
Over VCC Range; ISINK = 20 mA
VCC (V)
4.5 12.0 20.0
VOUT(SAT) by TA
0
50
100
150
200
500 450 400 350 300 250 200 150 100 50 0 0
Over TA Range; ISINK = 20 mA
TA (ºC)
150 25 40
VOUT(SAT) by VCC
Voltage (mV)
Voltage (mV)
5
10
15
20
25
Ambient Temperature, TA (ºC)
Supply Voltage, VCC (V)
Continued on next page.
A1425-DS Rev. 0a
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
5
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