ALLEGRO A3245 User Manual

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Package LH, 3-pin Surface Mount

GND

3

1

2

VCC

VOUT

A3245

Chopper-Stabilized

Omnipolar Hall-Effect Switches

The A3245 integrated circuit is an omnipolar, ultrasensitive Hall-effect switch
with a digital output. This sensor has an integrated regulator permitting operation
to 24 V, making it the fi rst omnipolar switch available for operation to 24 V. This
device is especially suited for operation over extended temperature ranges, up
to +150°C. Superior high-temperature performance is made possible through an
Allegro® patented dynamic offset cancellation, which reduces the residual offset
voltage normally caused by device overmolding, temperature excursions, and
thermal stress.

3

The A3245 Hall-effect switch includes the following on a single silicon chip:
voltage regulator, Hall-voltage generator, small-signal amplifi er, chopper stabiliza-
tion, Schmitt trigger, and a short circuit protected open-drain output. Advanced
BiCMOS wafer fabrication processing is used to take advantage of low-voltage
requirements, component matching, very low input-offset errors, and small com­ponent geometries.

Package UA, 3-pin SIP

1 32

VCC

GND

VOUT

1

2

3

AB SO LUTE MAX I MUM RAT INGS

Supply Voltage, V
Reverse-Supply Voltage, V
Reverse-Supply Current, I
Output Off Voltage, V
Output Current, I

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

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

..........................................28 V

CC

OUT

OUTSINK

, Range E..................–40ºC to 85ºC

A

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

A

........................–18 V

RCC

........................–2 mA

RCC

.................................. 28 V

........... Internally Limited

......................165ºC

J(MAX)

.................. –65ºC to 170ºC

S

The omnipolar operation of the A3245 allows activation with either a north or

a south polarity fi eld of suffi cient strength. In the absence of a magnetic fi eld,
the output is off. This patented magnetic-polarity-independence feature makes
this device an excellent replacement for reed switches, with improved ease of
manufacturing, because the A3245 does not require manufacturers to orient their
magnets. These devices allow simple on/off switching in industrial, consumer, and
automotive applications.

The A3245 is rated for operation between the ambient temperatures –40°C and
85°C for the E temperature range, and –40°C to 150°C for the L temperature
range. The small geometries of the BiCMOS process allow these devices to be
provided in ultrasmall packages. The package styles available provide magneti­cally optimized solutions for most applications. Package LH is an SOT23W, a
miniature low-profi le surface-mount package, while package UA is a three-lead
ultramini SIP for through-hole mounting. Each package is available in a lead (Pb)
free version, with 100% matte tin plated leadframes.

Features and Benefi ts

Omnipolar operation

Chopper stabilization

 Superior temperature stability

 Extremely low switchpoint drift

 Insensitive to physical stress

Reverse battery protection

Output short circuit protection

Solid state reliability

Small size

Robust EMC capability

High ESD ratings (HBM)

A3245-DS, Rev. 1

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

A3245

Chopper-Stabilized Omnipolar Hall Effect Switches

Product Selection Guide

Part Number Pb-Free Packing* Mounting

A3245ELHLT –

A3245ELHLT-T Yes

A3245EUA –

A3245EUA-T Yes

A3245LLHLT –

A3245LLHLT-T Yes

A3245LUA –

A3245LUA-T Yes

7-in. reel, 3000 pieces/reel 3-pin SOT23W surface mount

Bulk, 500 pieces/bag 3-pin SIP through hole

7-in. reel, 3000 pieces/reel 3-pin SOT23W surface mount

Bulk, 500 pieces/bag 3-pin SIP through hole

*Contact Allegro for additional packing options.

Functional Block Diagram

VCC

Regulator

To All Subcircuits

Ambient, T

(°C)

–40 to 85

–40 to 150

VOUT

A

A3245-DS, Rev. 1

Amp

Cancellation

Dynamic Offset

Amp

Sample and Hold

Filter

Low-Pass

Control

Current Limit

Terminal List

Name Description

VCC Connects power supply to chip 1 1

VOUT Output from circuit 2 3

GND Ground 3 2

Package LH Package UA

<1Ω

GND

Number

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

2

A3245

Chopper-Stabilized Omnipolar Hall Effect Switches

OPERATING CHARACTERISTICS valid over full operating voltage and ambient temperature ranges, unless otherwise noted

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Electrical Characteristics

Supply Voltage

Output Leakage Current I

Output On Voltage V

Output Current Limit I

Power-On Time t

Chopping Frequency f

Output Rise Time

Output Fall Time

Supply Current

Reverse Battery Current I

Supply Zener Clamp Voltage V

Supply Zener Current

Magnetic Characteristics

Operate Point

Release Point

Hysteresis

1

Maximum voltage must be adjusted for power dissipation and junction temperature, see Power Derating section.

2

CS = oscilloscope probe capacitance.

3

Maximum current limit is equal to the maximum I

4

Magnetic fl ux density, B, is indicated as a negative value for north-polarity magnetic fi elds, and as a positive value for south-polarity magnetic fi elds.
This so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the relative strength of the fi eld is indicated
by the absolute value of B, and the sign indicates the polarity of the fi eld (for example, a –100 G fi eld and a 100 G fi eld have equivalent strength, but
opposite polarity).

1

2

2

3

4

V

CC

OUTOFF

OUT(SAT)IOUT

OM

PO

c

t

r

t

f

I

CCON

I

CCOFF

RCC

ZSupply

I

ZSupply

B

OPS

B

OPN

B

RPS

B

RPN

B

HYS

Operating, TJ < 165°C 3.6 – 24 V

V

OUT

B > B

VCC > V

R

LOAD

R

LOAD

B > B

B < B

V

RCC

ICC = 6.5 mA; TA = 25°C 28 – – V

VS = 28 V – – 6.5 mA

South pole adjacent to branded face of device 15 38 55 G

North pole adjacent to branded face of device –55 –38 –15 G

South pole adjacent to branded face of device 5 20 50 G

North pole adjacent to branded face of device –50 –20 –5 G

|B

CC(MAX)

= 24 V, B < B

= 20 mA, B > B

OP

CC(MIN)

RP

OP

––10μA

– – 500 mV

30 – 60 mA

––50μs

– 200 – kHz

= 820 Ω, CS = 20 pF – – 1 μs

= 820 Ω, CS = 20 pF – – 1 μs

OP

RP

– 1.5 3.5 mA

– 1.5 3.5 mA

= –18 V – – –2 mA

– B

OPX

+ 3 mA.

RPX

|

51830G

A3245-DS, Rev. 1

DEVICE QUALIFICATION PROGRAM

Contact Allegro for information.

EMC (Electromagnetic Compatibility) REQUIREMENTS

Contact Allegro for information.

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

3

A3245

Chopper-Stabilized Omnipolar Hall Effect Switches

Electrical Characteristic Data

Supply Current (On) versus Ambient Temperature

5.0

4.0

3.0

(mA)

2.0

CCON

I

1.0

0

–50 0 50 100 150

TA (°C)

Supply Current (Off) versus Ambient Temperature

5.0

4.0

3.0

(mA)

2.0

CCOFF

I

VCC (V)

VCC (V)

Supply Current (On) versus Supply Voltage

5.0

4.0

24

3.6

3.0

(mA)

2.0

CCON

I

1.0

0

0 5 10 15 20 25

VCC (V)

Supply Current (Off) versus Supply Voltage

5.0

4.0

3.0

24

3.6

(mA)

2.0

CCOFF

I

TA (°C)

–40

25

150

TA (°C)

–40

25

150

1.0

0

–50 0 50 100 150

TA (°C)

Output Voltage (On) versus Ambient Temperature

500

450

400

350

300

(mV)

250

200

OUT(SAT)

150

V

100

50

0

–50 0 50 100 150

TA (°C)

VCC (V)

24

3.6

1.0

0

0 5 10 15 20 25

VCC (V)

Output Voltage (On) versus Supply Voltage

500

450

400

350

300

(mV)

250

200

OUT(SAT)

150

V

100

50

0

0 5 10 15 20 25

VCC (V)

TA (°C)

–40

25

150

A3245-DS, Rev. 1

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

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