A1146 Allegro MicroSystems, A1146 Datasheet

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A1146

Manufacturer Part Number
A1146
Description
(A1145 / A1146) Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Manufacturer
Allegro MicroSystems
Datasheet
Features and Benefits
▪ Chopper stabilization
▪ Factory programmed at end-of-line for optimized
▪ On-chip protection
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
Not to scale
A1145-DS, Rev. 8
switchpoints
▫ Low switchpoint drift over operating
▫ Low sensitivity to stress
▫ Supply transient protection
▫ Reverse-battery protection
▫ On-board voltage regulator
▫ 3.5 to 24 V operation
temperature range
V+
0.01 uF
VCC
Ultrasensitive Two-Wire Chopper-Stabilized
Functional Block Diagram
Clock/Logic
Amp
www.DataSheet4U.com
Low-Pass
Filter
Unipolar Hall Effect Switches
Description
The A1145 and A1146 devices are two-wire, unipolar, Hall
effect switches that are factory-programmed at end-of-line to
optimize ultrasensitive magnetic switchpoint accuracy. These
devices use a patented high frequency chopper-stabilization
technique, produced using the Allegro advanced BiCMOS
wafer fabrication process, to achieve magnetic stability and
to eliminate offset inherent in single-element devices exposed
to harsh application environments.
Commonly found in a number of automotive applications,
these switches are utilized to sense seat track position, seat
belt buckle presence, hood/trunk latching, and shift selector
position. Two-wire unipolar switches, such as the A1145
and A1146, are particularly advantageous in price-sensitive
applications because they require one less wire for operation
than do switches with the more traditional open-collector output.
Additionally, the system designer inherently gains diagnostics
because there is always output current flowing, which should
be in either of two narrow ranges. Any current level not within
these ranges indicates a fault condition. These devices also
Continued on the next page…
Regulator
To All Subcircuits
Package UA Only
GND
A1145 and A1146
GND

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A1146 Summary of contents

Page 1

... A1145-DS, Rev. 8 Unipolar Hall Effect Switches Description The A1145 and A1146 devices are two-wire, unipolar, Hall effect switches that are factory-programmed at end-of-line to optimize ultrasensitive magnetic switchpoint accuracy. These devices use a patented high frequency chopper-stabilization technique, produced using the Allegro advanced BiCMOS ...

Page 2

... Description (continued) feature on-chip transient protection and a Zener clamp to protect against overvoltage conditions on the supply line. The output currents of the A1146 switches HIGH in the presence of a south (+) polarity magnetic field of sufficient strength, and switches LOW otherwise the presence of a weak field or a north (– ...

Page 3

... Unipolar Hall Effect Switches over the operating voltage and temperature ranges, unless otherwise specified Test Conditions > B for A1145; B < B for A1146 CCL > B for A1146; B < B for A1145 CCH –18 V RCC RCC mA 25°C ...

Page 4

... Various Levels (A1145 and A1146) – 100 150 Ambient Temperature, T (° Various Levels (A1145 and A1146 – 100 150 Ambient Temperature, T (°C) A Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www ...

Page 5

... A1145 and A1146 THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Package Thermal Resistance *Additional thermal information available on Allegro Web site. Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches Symbol Test Conditions* Package LH, 1-layer PCB with copper limited to solder pads Package LH, 2-layer PCB with 0 ...

Page 6

... Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches Functional Description clean switching of the output even in the presence of external mechanical vibration and electrical noise. The A1146 device switches with opposite polarity for similar B in comparison to the A1145 (see figure 1). I CC(H) ...

Page 7

... A1145 and A1146 Chopper Stabilization Technique When using Hall-effect technology, a limiting factor for switchpoint accuracy is the small signal voltage developed across the Hall element. This voltage is disproportionally small relative to the offset that can be produced at the output of the Hall sensor. This makes it difficult to process the signal while maintaining an accurate, reliable output over the specified oper- ating temperature and voltage ranges ...

Page 8

... A1145 and A1146 Typical Application Circuit The A114x family of devices must be protected by an external bypass capacitor connected between the supply, VCC, BYP and the ground, GND, of the device. C noise and the noise generated by the chopper-stabilization func- tion. As shown in figure 3, a 0.01 μF capacitor is typical. ...

Page 9

... A1145 and A1146 Power Derating The device must be operated below the maximum junction temperature of the device Under certain combinations of J(max) peak conditions, reliable operation may require derating sup- plied power or improving the heat dissipation properties of the application. This section presents a procedure for correlating factors affecting operating T ...

Page 10

... A1145 and A1146 EMC (Electromagnetic Compatibility) Requirements Package LH, 3-pin SOT VCC connection 3. GND Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches Device Qualification Program Contact Allegro for information. Contact your local representative for EMC results. Test Name Reference Specification ESD – ...

Page 11

... A1145 and A1146 Preliminary dimensions, for reference only Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only (reference JEDEC TO-236 AB, except case width and terminal tip-to-tip) Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown ...

Page 12

... A1145 and A1146 .122 .117 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; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec tions as may be required to permit improvements in the per for mance, reliability, or manufacturability of its products ...

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