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 first 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 amplifier, chopper stabilization, 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.
The omnipolar operation of the A3245 allows activation with
either a north
or
a south polarity field of sufficient strength. In
the absence of a magnetic field, the output is off. This patented
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
Continued on the next page…
Not to scale
Functional Block Diagram
VCC
Regulator
To All Subcircuits
Sample and Hold
Dynamic Offset
Cancellation
Low-Pass
Filter
VOUT
Amp
Amp
Control
Current Limit
<1Ω
GND
A3245-DS, Rev. 2
A3245
Chopper-Stabilized Omnipolar Hall Effect Switches
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-profile 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.
Description (continued)
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
Selection Guide
Part Number
A3245ELHLT-T
A3245EUA-T
A3245LLHLT-T
A3245LUA-T
1
Pb-based
Pb-Free
1
Yes
Yes
Yes
Yes
Packing
2
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
Mounting
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SIP through hole
Ambient, T
A
(°C)
–40 to 85
–40 to 150
variants are being phased out of the product line. Certain variants cited in this footnote are in production but have been determined to be NOT
FOR NEW DESIGN. This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be
purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: May 1, 2006.
These variants include: A3245ELHLT, A3245EUA, A3245LLHT, and A3245LUA.
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