A3245
A3245-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
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.
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 com-
ponent geometries.
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 magneti-
cally 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.
AB SO LUTE MAX I MUM RAT INGS
Supply Voltage, V
CC
..........................................28 V
Reverse-Supply Voltage, V
RCC
........................–18 V
Reverse-Supply Current, I
RCC
........................–2 mA
Output Off Voltage, V
OUT
..................................28 V
Output Current, I
OUTSINK
........... Internally Limited
Magnetic Flux Density, B .........................Unlimited
Operating Temperature
Ambient, T
A
, Range E..................–40ºC to 85ºC
Ambient, T
A
, Range L................–40ºC to 150ºC
Maximum Junction, T
J(MAX)
......................165ºC
Storage Temperature, T
S
..................–65ºC to 170ºC
Chopper-Stabilized
Omnipolar Hall-Effect Switches
Package LH, 3-pin Surface Mount
Features and Benefi ts
Package UA, 3-pin SIP
Omnipolar operation
Chopper stabilization
null Superior temperature stability
null Extremely low switchpoint drift
null Insensitive to physical stress
Reverse battery protection
Output short circuit protection
Solid state reliability
Small size
Robust EMC capability
High ESD ratings (HBM)
1 32
VCC GND
VOUT
1 2
3
VCC
VOUT
GND
1
2
3
1
2
3