ALLEGRO A3250 User Manual

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Package UA, 3-pin SIP

A3250 and A3251

Field-Programmable, Chopper-Stabilized

Unipolar Hall-Effect Switches

The A3250 and A3251 are field-programmable, chopper-stabilized, unipolar Halleffect switches designed for use in high-temperature applications. These devices use a chopper-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 programmability of the magnetic operate point (B teresis remains fixed. This advanced feature allows for optimization 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.

) while the hys-

TL Option

231

1. VCC

2. GND

3. VOUT

AB SO LUTE MAX I MUM RAT INGS

Supply Voltage, VCC ......................................26.5 V

Reverse-Supply Voltage, V Zener Overvoltage, V Output Current, I

Magnetic Flux Density, B.........................Unlimited

Operating Temperature Ambient, T Ambient, T Maximum Junction, T Storage Temperature, T

.........................................20 mA

OUT

, Range J................. –40ºC to 115ºC

, Range L................–40ºC to 150ºC

........................–18 V

RCC

.......................................30 V

........................165ºC

J(max)

.................. –65ºC to 170ºC

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 HIGH when the field drops below the magnetic release point, B

, and switches

. The output of

the A3251 has the opposite polarity, switching HIGH in a south-polarity magnetic field that B

, and switching LOW when the field drops below B

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.

These devices are available in a TO-92 three-lead ultra-mini SIP (Single In-line Package), with either straight or formed and trimmed lead configuration.

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

Use the following complete part numbers when ordering:

Part Number Package

A3250JUA A3250JUATL

A3250LUA A3250LUATL

A3251JUA A3251JUATL

A3251LUA A3251LUATL

*In south polarity magnetic field of sufficient strength.

Straight lead Formed lead

(ºC)

–40 to 115 18

–40 to 150 13

–40 to 115 18

–40 to 150 13

On-chip protection against:

 Supply transients

 Output short-circuits

 Reverse-battery condition

hys(typ)

(G)

Power-On Running*

OUT

High Low

Low High

A3250-DS

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

A3250 and A3251

HYS

Switch to High

Switch to Low

B+

OUT(off)

OUT

OUT(on)(sat)

V+

Hysteresis of ∆V

OUT

Switching Due to ∆B

Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches

Functional Block Diagram

VCC

Program/Lock

Programming

Logic

Regulator

A3250

Hysteresis of ∆V

Switching Due to ∆B

V+

OUT

Switch to Low

Offset Adjust

Amp

Cancellation

Dynamic Offset

Low-Pass

Sample and Hold

Filter

Current Limit

GND

VOUT

Hysteresis Curves

A3251

OUT(off)

A3250-DS

OUT

Switch to High

HYS

OUT(on)(sat)

B+

Output voltage in relation to sensed magnetic flux density in a south polarity magnetic field of sufficient strength. Transition through B

must precede transition through BRP.

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

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. Typ. Max. Units

ELECTRICAL CHARACTERISTICS

Supply Voltage

Output Saturation Voltage V

Output Leakage Current I

Supply Current

Output Rise Time t

Output Fall Time t

Chopping Frequency f

Power-Up Time t

Output Current Limit

1,2

Power-On State POS

MAGNETIC CHARACTERISTICS

OUT(sat)IOUT

OFF

Running mode 4.2 – 24 V

A3250; B < BRP; V

CC(off)

A3251; B > B

A3250; B > BOP; V

CC(on)

OUT(lim)

A3251; B < B

Short-circuit protection 60 90 120 mA

A3250; B < B

A3251; B < B

= 20 mA; Switch state = ON – 175 400 mV

= 24 V; Switch state = OFF – – 10 µA

OUT

= HIGH – 4.0 7.0 mA

OUT

; V

= 820 Ω, C

LOAD

= 820 Ω, C

LOAD

= HIGH – 20 50 µs

OUT

= HIGH – 4.0 7.0 mA

OUT

= LOW – 6.0 10.0 mA

OUT

; V

= LOW – 6.0 10.0 mA

OUT

= 10 pF – – 5.0 µs

LOAD

= 10 pF – – 5.0 µs

LOAD

, t > t

– 340 – kHz

– HIGH – mV

– LOW – mV

Initial Operate Point B

Temperature Drift of B

∆B

BOP ≤ 500 gauss –35 – 35 G

–20 13 50 G

Package TA range = J 5.0 18 35 G

Hysteresis (B

– BRP)B

hys

Package T

range = L 5.0 13 35 G

PROGRAMMING CHARACTERISTICS

Programmable B

Values

OP(prog)

50 – ≥350 G

Switchpoint set – 6 – Bit

Number of Programming Bits –

Programming lock – 1 – Bit

Resolution B

RES

– 7.0 – G

TRANSIENT PROTECTION CHARACTERISTICS

Supply Zener Voltage V

Supply Zener Current I

Reverse Battery Current I

Do not exceed TJ(max): Additional information on power derating is provided in the applications section.

Short-circuit protection is not intended for continuous operation; permanent damage may result.

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.

RCC

VCC = 28 V – – 13 mA

= –18 V, TJ < T

RCC

J(max)

28 – – V

– – –5.0 mA

A3250-DS

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

A3250 and A3251

Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches

Typical Characterization Data

All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot

Average BOPvs. T

Program Code: 1, VCC=12V

(G)Average B

Average B

-5

-50 -20 10 40 70 100 130 160

(°C)

Average BOPvs. T

Program Code: 8, VCC=12V

(G)Average B

-50 -20 10 40 70 100 130 160

(°C)

Average BRPvs. T

Program Code: 1, VCC=12V

(G)Average B

-5

-10

Average B

-15

-20

-50 -20 10 40 70 100 130 160

TA(°C)

Average BRPvs. T

Program Code: 8, VCC=12V

(G)Average B

-50 -20 10 40 70 100 130 160

(°C)

130

125

(G)

120

115

110

105

100

A3250-DS

Average BOPvs. T

Program Code: 16, VCC=12V

-50 -20 10 40 70 100 130 160

(°C)

Average BRPvs. T

Program Code: 16, VCC=12V

110

105

(G)

100

-50 -20 10 40 70 100 130 160

(°C)

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

A3250 and A3251

-40°C to 25°C and 150°C to 25°C

-30

-20

-10

Code 1

Code 8

Code 16

-40°C to 25°C

150°C to 25°C

Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches

Typical Characterization Data

All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot

Average B Program Code: 1, V

vs. Temperature

hys

=12V

(G)

HYS

Average B

-50 -20 10 40 70 100 130 160

(°C)

Average B

Program Code: 8, V

vs. Temperature

hys

=12V

(G)

HYS

20 15

Average B

-50 -20 10 40 70 100 130 160

(°C)

Average B

Program Code: 16, V

vs. Temperature

hys

=12V

(G)

HYS

Average B

-50 -20 10 40 70 100 130 160

TA(°C)

Average BOPvs. Temperature

(G)

Average B

(°C)

A3250-DS

Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

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