A3250ELT-T ALLEGRO [Allegro MicroSystems], A3250ELT-T Datasheet

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A3250ELT-T

Manufacturer Part Number
A3250ELT-T
Description
Field-Programmable, Chopper-Stabilized Unipolar Hall-Effect Switches
Manufacturer
ALLEGRO [Allegro MicroSystems]
Datasheet
Features and Benefits
▪ Chopper stabilization for stable switchpoints throughout
▪ Externally programmable operate point (through VCC
▪ On-board voltage regulator for 4.2 V to 24 V operation
▪ On-chip protection against:
Package: 3 pin SOT89 (suffix LT) and
3 pin SIP (suffix UA)
Not to scale
3250-DS Rev. 3
operating temperature range
pin)
▫ Supply transients
▫ Output short-circuits
▫ Reverse-battery condition
VCC
Amp
Field-Programmable, Chopper-Stabilized
Functional Block Diagram
Program/Lock
Programming
Logic
Low-Pass
Filter
Offset Adjust
Unipolar Hall-Effect Switches
Description
The A3250 and A3251 are field-programmable, chopper-
stabilized, unipolar Hall-effect switches designed for use in
high-temperature applications. These devices use a chop-
per-stabilization technique to eliminate offset inherent in
single-element devices.
The A3250 and A3251 are externally programmable
devices. The devices have a wide range of programmabil-
ity of the magnetic operate point (B
remains fixed. This advanced feature allows for optimiza-
tion of the sensor switchpoint and can drastically reduce
the effects of variations found in a production environment,
such as magnet and device placement tolerances.
These devices provide on-chip transient protection. A Zener
clamp on the power supply protects against overvoltage
conditions on the supply line. These devices also include
short-circuit protection on the output.
The output of the A3250 switches LOW when subjected
to a south-polarity magnetic field with a flux density that
exceeds the threshold for B
Continued on the next page…
Current Limit
Regulator
A3250 and A3251
OP
GND
, and switches HIGH when the
OP
) while the hysteresis
VOUT

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A3250ELT-T Summary of contents

Page 1

Features and Benefits ▪ Chopper stabilization for stable switchpoints throughout operating temperature range ▪ Externally programmable operate point (through VCC pin) ▪ On-board voltage regulator for 4 operation ▪ On-chip protection against: ▫ Supply transients ▫ ...

Page 2

... RP The other differences in the devices are the power-on state. The A3250 powers-on in the HIGH state, while the A3251 powers-on in the LOW state. Selection Guide 1 Part Number Pb-free A3250ELT-T Yes Bulk, 500 pieces/bag A3250ELTTR-T Yes 7-in. reel, 1000 pieces/reel A3250EUA-T Yes Bulk, 500 pieces/bag ...

Page 3

A3250 and A3251 OPERATING CHARACTERISTICS valid over operating T Characteristic Symbol ELECTRICAL CHARACTERISTICS Supply Voltage 1 Output Saturation Voltage V Output Leakage Current Supply Current Output Rise Time Output Fall Time Chopping Frequency Power-Up Time Output Current Limit 1,2 I ...

Page 4

A3250 and A3251 All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot Average B vs Program Code -50 - ...

Page 5

A3250 and A3251 All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot Average B vs. Temperature hys Program Code -50 - ...

Page 6

A3250 and A3251 All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot Average I vs. Temperature CC(on -50 - (°C) A 280 260 240 ...

Page 7

A3250 and A3251 THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Package Thermal Resistance Power Derating Curve 1-layer PCB, Package 180 ºC/W) θJA ...

Page 8

A3250 and A3251 Chopper-Stabilized Technique The Hall sensor is based on a Hall element, a small sheet of semiconductor material in which a constant bias current flows when a constant voltage source is applied. The output takes the form of ...

Page 9

A3250 and A3251 Programming Protocol The operate switchpoint can be field-programmed so, a coded series of voltage pulses through the VCC pin is used to set bitfields in onboard registers. The effect on the device ...

Page 10

A3250 and A3251 The pulse sequences consist of the following groups of pulses enable sequence bitfield address sequence. 3. When permanently setting the bitfield, a long V ing pulse. (Note: Blown bit fuses cannot be reset.) ...

Page 11

A3250 and A3251 The first segment of code is a Enabling Addressing Mode. keying sequence used to enable the bitfield addressing mode. As shown in figure 4, this segment consists of one short V seven or more V pulses, and ...

Page 12

A3250 and A3251 For additional general application information, visit the Allegro MicroSystems Web site at www. allegromicro.com. Typical Application Circuit It is strongly recommended that an external ceramic bypass capacitor the range of 0.01 μF to 0.1 ...

Page 13

A3250 and A3251 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 ...

Page 14

A3250 and A3251 4.25 3.94 2X Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches Package LT, 3-Pin SOT89 4.60 .181 4.40 .173 1.83 .072 1.62 .064 1.14 .0450 NOM 2.60 .102 2.29 .090 .167 A .155 0.48 .019 0.36 .014 ...

Page 15

A3250 and A3251 .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. ...

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