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Hall-Effect Switches. A3251 Datasheet

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Hall-Effect Switches. A3251 Datasheet






A3251 Switches. Datasheet pdf. Equivalent




A3251 Switches. Datasheet pdf. Equivalent





Part

A3251

Description

(A3250 / A3251) Chopper-Stabilized Unipolar Hall-Effect Switches



Feature


A3250 and A3251 Field-Programmable, Chop per-Stabilized Unipolar Hall-Effect Swi tches Features and Benefits ▪ Chopper stabilization for stable switchpoints throughout operating temperature range ▪ Externally programmable operate poi nt (through VCC pin) ▪ On-board volta ge regulator for 4.2 V to 24 V operatio n ▪ On-chip protection against: ▫ S upply transients ▫ Output sh.
Manufacture

Allegro MicroSystems

Datasheet
Download A3251 Datasheet


Allegro MicroSystems A3251

A3251; ort-circuits ▫ Reverse-battery conditi on Description The A3250 and A3251 are field-programmable, chopperstabilized, unipolar Hall-effect switches designed for use in high-temperature applicatio ns. These devices use a chopper-stabili zation technique to eliminate offset in herent in single-element devices. The A 3250 and A3251 are externally programma ble devices. The dev.


Allegro MicroSystems A3251

ices have a wide range of programmabilit y of the magnetic operate point (BOP) w hile the hysteresis remains fixed. This advanced feature allows for optimizati on of the sensor switchpoint and can dr astically reduce the effects of variati ons found in a production environment, such as magnet and device placement tol erances. These devices provide on-chip transient protecti.


Allegro MicroSystems A3251

on. A Zener clamp on the power supply pr otects against overvoltage conditions o n the supply line. These devices also i nclude short-circuit protection on the output. The output of the A3250 switche s LOW when subjected to a south-polarit y magnetic field with a flux density th at exceeds the threshold for BOP , and switches HIGH when the Package: 3 pin SOT89 (suffix LT) .

Part

A3251

Description

(A3250 / A3251) Chopper-Stabilized Unipolar Hall-Effect Switches



Feature


A3250 and A3251 Field-Programmable, Chop per-Stabilized Unipolar Hall-Effect Swi tches Features and Benefits ▪ Chopper stabilization for stable switchpoints throughout operating temperature range ▪ Externally programmable operate poi nt (through VCC pin) ▪ On-board volta ge regulator for 4.2 V to 24 V operatio n ▪ On-chip protection against: ▫ S upply transients ▫ Output sh.
Manufacture

Allegro MicroSystems

Datasheet
Download A3251 Datasheet




 A3251
A3250 and A3251
Field-Programmable, Chopper-Stabilized
Unipolar Hall-Effect Switches
Features and Benefits
Chopper stabilization for stable switchpoints throughout
operating temperature range
Externally programmable operate point (through VCC pin)
On-board voltage regulator for 4.2 V to 24 V operation
On-chip protection against:
Supply transients
Output short-circuits
Reverse-battery condition
Package: 3-pin SOT89 (suffix LT) and
3-pin SIP (suffix UA)
Not to scale
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 (BOP) while the hysteresis
remains fixed. This advanced feature allows for optimiza-
tion of the device 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 BOP, and switches HIGH when the
field drops below the magnetic release point, BRP. The out-
put of the A3251 has the opposite polarity, switching HIGH
in a south-polarity magnetic field that BOP, and switching
LOW when the field drops below BRP.
Continued on the next page…
Functional Block Diagram
VCC
Program/Lock
Programming
Logic
Offset Adjust
Regulator
Amp
Low-Pass
Filter
Current Limit
VOUT
3250-DS Rev. 11
GND




 A3251
A3250 and
A3251
Field-Programmable, Chopper-Stabilized,
Unipolar Hall-Effect Switches
Description (continued)
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.
Three package styles provide a magnetically optimized package
for most applications. Type LT is a miniature SOT89/TO-243AA
surface mount package that is thermally enhanced with an
exposed ground tab, and type UA is a three-lead ultramini SIP
for through-hole mounting. The packages are lead (Pb) free, with
100% matte tin plated leadframes (suffix, –T).
Selection Guide
Part Number
Packing1
A3250LLTTR-T
7-in. reel, 1000 pieces/reel
1Contact Allegro for additional packing options.
2In south polarity magnetic field of sufficient strength.
Package
Surface mount
TA
(ºC)
–40 to 150
VOUT
Power-On Running2
High
Low
Absolute Maximum Ratings
Characteristic
Supply Voltage
Reverse Supply Voltage
Zener Overvoltage
Output Current
Magnetic Flux Density
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
VCC
VRCC
VZ
IOUT
B
TA
TJ(max)
Tstg
Range E
Range L
Notes
Rating
26.5
–18
30
20
Unlimited
–40 to 85
–40 to 150
165
–65 to 170
Units
V
V
V
mA
G
ºC
ºC
ºC
ºC
Pin-out Diagrams
12 3
123
LT
Terminal List
Number
1
Name
VCC
2 GND
3 VOUT
Function
Connects power supply to chip
Ground
Device output
UA
Allegro MicroSystems, Inc.
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com




 A3251
A3250 and
A3251
Field-Programmable, Chopper-Stabilized,
Unipolar Hall-Effect Switches
OPERATING CHARACTERISTICS valid over operating TA and VCC, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
ELECTRICAL CHARACTERISTICS
Supply Voltage1
VCC
Output Saturation Voltage
VOUT(sat)
Output Leakage Current
IOFF
Supply Current
Output Rise Time
Output Fall Time
Chopping Frequency
Power-Up Time
Output Current Limit1,2
ICC(off)
ICC(on)
tr
tf
fC
ton
IOUT(lim)
Power-On State
POS
MAGNETIC CHARACTERISTICS
Running mode
IOUT = 20 mA; Switch state = ON
VOUT = 24 V; Switch state = OFF
A3250; B < BRP; VOUT = HIGH
A3251; B > BOP; VOUT = HIGH
A3250; B > BOP; VOUT = LOW
A3251; B < BRP; VOUT = LOW
RLOAD = 820 Ω, CLOAD = 10 pF
RLOAD = 820 Ω, CLOAD = 10 pF
VOUT = HIGH
Short-circuit protection
A3250; B < BRP, t > ton
A3251; B < BRP, t > ton
4.2
60
Initial Operate Point
Temperature Drift of BOP
Hysteresis (BOP – BRP)
BOP
ΔBOP
Bhys
PROGRAMMING CHARACTERISTICS
Programmable BOP Values3
BOP(prog)
Number of Programming Bits
BOP 500 gauss
Package TA range = J
Package TA range = L
Switchpoint set
Programming lock
–20
–35
5.0
5.0
50
Resolution
BRES
TRANSIENT PROTECTION CHARACTERISTICS
Supply Zener Voltage
Supply Zener Current
Reverse Battery Current
VZ
IZ
IRCC
VCC = 28 V
VRCC = –18 V, TJ < TJ(max)
28
Typ.
175
4.0
4.0
6.0
6.0
340
20
90
HIGH
LOW
13
18
13
6
1
7.0
Max.
24
400
10
7.0
7.0
10.0
10.0
5.0
5.0
50
120
50
35
35
35
350
13
–5.0
Units
V
mV
μA
mA
mA
mA
mA
μs
μs
kHz
μs
mA
mV
mV
G
G
G
G
G
Bit
Bit
G
V
mA
mA
1 Do not exceed TJ(max): Additional information on power derating is provided in the applications section.
2 Short-circuit protection is not intended for continuous operation; permanent damage may result.
3 Device can be used below 50 G but is not guaranteed to be a unipolar switch. It is the responsibility of the programmer to verify that the desired
switchpoint has been achieved.
Allegro MicroSystems, Inc.
3
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com






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