The A3212 integrated circuit is an ultra-sensitive, pole in de pen dent Hall-
effect switch with a latched digital output. This sensor is es pe cial ly suited for
operation in battery-operated, hand-held equip ment such as cellular and cordless
tele phones, pagers, and palmtop com put ers. A 2.5 volt to 3.5 volt operation and a
unique clocking scheme reduce the average op er at ing power requirements to less
than 15 µW with a 2.75 volt supply.
Unlike other Hall-effect switches, either a north or south pole of suf fi cient
strength will turn the output on; in the absence of a magnetic fi eld, the output
is off. The polarity independence and minimal power requirement allow these
devices to easily replace reed switches for superior reliability and ease of manu-
facturing, while eliminating the requirement for signal conditioning.
Improved stability is made possible through chopper stabilization (dynamic
offset cancellation), which reduces the residual offset voltage normally caused
by device overmolding, temperature de pen den cies, and thermal stress.
This device includes on a single silicon chip a Hall-voltage generator,
small-signal amplifi er, chopper sta bi li za tion, a latch, and a MOSFET output.
Ad vanced BiCMOS processing is used to take advantage of low-voltage and
low-power requirements, component matching, very low input-offset errors, and
small component geometries.
Three package styles provide a magnetically op ti mized pack age for most ap-
pli ca tions. Package suffi xes 'EH' and ‘LH’ are for miniature low-profi le (lead-
less and leaded, respectively) surface-mount packages while suffi x ‘UA’ is for
a three-lead SIP for through-hole mount ing. Each package is available in a lead
(Pb) free version (suffi x, –T) with 100% matte tin plated leadframe.
FEATURES
■ Micropower Operation
■ Operation with North or South Pole
■ 2.5 V to 3.5 V Battery Operation
■ Chopper Stabilized
Superior Temperature Stability
Extremely Low Switch-Point Drift
Insensitive to Physical Stress
■ ESD Protected to 5 kV
■ Sol id-State Reliability
■ Small Size
■Easily Manufacturable with Magnet Pole Independence
Data Sheet
27622.61D
Package Suffi x ‘LH’ Pinning
(SOT23W)
A3212
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VDD .............................. 5 V
Magnetic Flux Density, B .......... Unlimited
Output Off Voltage, VOUT ...................... 5 V
Output Current, IOUT ........................... 1 mA
Junction Temperature, TJ ................ +170°C
Operating Temperature, TA
Range 'E-' .................... -40°C to +85°C
Range 'L-' .................. -40°C to +150°C
Storage Temperature Range,
TS .............................. -65°C to +170°C
Caution: These CMOS devices have input
static protection (Class 3) but are still sus-
ceptible to damage if exposed to extremely
high static electrical charges.
Pinning is shown viewed from branded side.
MICROPOWER, ULTRA-SENSITIVE
HALL-EF FECT SWITCH
Dwg. PH-016-1
SUPPLY
GROUND
OUTPUT
V
DD
12
3
A3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
2
Product Selection Guide
Use complete part numbers when ordering
Part Number Pb-free Packing*
(Units/Pack) Package
Ambient
Temperature
TA (°C)
A3212EEHLT – Tape and Reel (3000) Leadless Surface Mount
–40 to 85
A3212EEHLT–T Yes Tape and Reel (3000)
A3212ELHLT – Tape and Reel (3000) 3-Pin Surface Mount
A3212ELHLT–T Yes Tape and Reel (3000)
A3212EUA – Bulk Pack (500) SIP-3 Through Hole, Straight Lead
A3212EUA–T Yes Bulk Pack (500)
A3212LLHLT – Tape and Reel (3000) 3-Pin Surface Mount
–40 to 150
A3212LLHLT–T Yes Tape and Reel (3000)
A3212LUA – Bulk Pack (500) SIP-3 Through Hole, Straight Lead
A3212LUA–T Yes Bulk Pack (500)
*Contact Allegro for additional packaging and handling options.
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
www.allegromicro.com
3
FUNCTIONAL BLOCK DIAGRAM
Copyright © 2002, 2003 Allegro MicroSystems, Inc.
Package Suffi x ‘UA’ Pinning
(SIP)
Pinning is shown viewed from branded side.
Package Suffi x ‘EH’ Pinning
(Leadless Chip Carrier)
TIMING
LOGIC
Dwg. FH-020-5
LATCH
GROUND
OUTPUT
SUPPLY
X
DYNAMIC
OFFSET CANCELLATION
SWITCH
SAMPLE
& HOLD
X
Dwg. PH-016-2
SUPPLY
GROUND
OUTPUT
V
DD
GROUND
NO
CONNECTION
NO
CONNECTION
54
6
13
2
Dwg. PH-016
1
SUPPLY
VDD
GROUND
32
OUTPUT
X
A3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
4
ELECTRICAL CHARACTERISTICS over operating voltage and temperature range (unless
otherwise specified).
Limits
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Operate Points BOPS South pole to branded side – 37 55 G
BOPN North pole to branded side -55 -40 – G
Release Points BRPS South pole to branded side 10 31 – G
BRPN North pole to branded side – -34 -10 G
Hysteresis Bhys |BOPx - BRPx|–5.9–G
NOTES: 1. Negative flux densities are defined as less than zero (algebraic convention), i.e., -50 G is less than +10 G.
2. BOPx = operate point (output turns on); BRPx = release point (output turns off).
3. Typical Data is at TA = +25°C and VDD = 2.75 V and is for design information only.
4. 1 gauss (G) is exactly equal to 0.1 millitesla (mT).
MAGNETIC CHARACTERISTICS over operating voltage and temperature range (unless
otherwise specified).
Limits
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Supply Voltage Range VDD Operating12.5 2.75 3.5 V
Output Leakage Current IOFF VOUT = 3.5 V, BRPN < B < BRPS –<1.01.0µA
Output On Voltage VOUT IOUT = 1 mA, VDD = 2.75 V – 100 300 mV
Awake Time tawake –4590µs
Period tperiod –4590ms
Duty Cycle d.c. – 0.1 – %
Chopping Frequency fC– 340 – kHz
Supply Current IDD(EN) Chip awake (enabled) – – 2.0 mA
IDD(DIS) Chip asleep (disabled) – – 8.0 µA
IDD(AVG) VDD = 2.75 V – 5.1 10 µA
VDD = 3.5 V – 6.7 10 µA
NOTES: 1. Operate and release points will vary with supply voltage.
2. BOPx = operate point (output turns on); BRPx = release point (output turns off).
3. Typical Data is at TA = +25°C and VDD = 2.75 V and is for design information only.
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
www.allegromicro.com
5
TYPICAL OPERATING CHARACTERISTICS
SUPPLY CURRENT
SWITCH POINTS
0 50 100
AMBIENT TEMPERATURE IN °°
°°C
-50
Dwg. GH-027-3
SWITCH POINTS IN GAUSS
0
20
40
-20
-40
V
DD
= 2.75 V
150
60
-60 -25 25 75 125
B
OPS
B
RPS
B
RPN
B
OPN
0255075
100
AMBIENT TEMPERATURE IN °°
°°C
-50
Dwg. GH-028-1
1
125
-25
AVERAGE SUPPLY CURRENT IN µµ
µµA
7.0
6.0
5.0
3.0
V
DD
=3.5 V
15
0
V
DD
=2.75 V
V
DD
=2.5 V
4.0
7.0
AVERAGE SUPPLY CURRENT IN µµ
µµA
6.0
5.0
4.0
3.0 2.8 3.0 3.2 3.4 3.6
SUPPLY VOLTAGE IN VOLTS
2.4
Dwg. GH-058-7
2.6
T
A
= 25°C
A3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
6
FUNCTIONAL DESCRIPTION
Low Average Power. Internal timing circuitry activates the
sensor for 45 µs and deactivates it for the remainder of the pe-
riod (45 ms). A short "awake" time allows for stabilization prior
to the sensor sam pling and data latching on the falling edge of
the timing pulse. The output during the "sleep" time is latched in
the last sampled state. The supply current is not affected by the
output state.
Chopper-Stabilized Technique. The Hall element can be
considered as a resistor array similar to a Wheatstone bridge. A
large portion of the offset is a result of the mismatching of these
resistors. These devices use a proprietary dynamic offset cancel-
lation technique, with an internal high-frequency clock to reduce
the residual offset voltage of the Hall element that is normally
caused by device overmolding, temperature de pen den cies, and
thermal stress. The chopper-stabilizing technique cancels the
mismatching of the resistor circuit by changing the direction of
the current fl owing through the Hall plate using CMOS switches
and Hall voltage measurement taps, while maintaing the Hall-
voltage signal that is induced by the external magnetic fl ux. The
signal is then captured by a sample-and-hold circuit and further
processed using low-offset bipolar circuitry. This technique
produces devices that have an extremely stable quiescent Hall
output voltage, are immune to thermal stress, and have precise
recoverability after temperature cycling. A relatively high sam-
pling frequency is used for faster signal processing capability
can be processed.
More detailed descriptions of the circuit operation can be
found in: Technical Paper STP 97-10, Monolithic Magnetic Hall
Sensor Using Dynamic Quadrature Offset Cancellation and
Technical Paper STP 99-1, Chopper-Stabilized Amplifi ers With A
Track-and-Hold Signal Demodulator.
Dwg. WH-017-2
0
PERIOD
"AWAKE"
"SLEEP"
IDD(EN)
IDD(DIS)
SAMPLE &
OUTPUT LATCHED
+V
HALL
VOLTAGE
B
+
—
Dwg. AH-011-2
Dwg. EH-012-1
SAMPLE
& HOLD
X
+V
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
www.allegromicro.com
7
Operation. The output of this device switches low (turns on)
when a magnetic fi eld perpendicular to the Hall sensor exceeds
the operate point BOPS (or is less than BOPN). After turn-on, the
output is capable of sinking up to 1 mA and the output voltage is
VOUT(ON). When the magnetic fi eld is reduced below the release
point BRPS (or increased above BRPN), the device output switch-
es high (turns off). The dif fer ence in the magnetic operate and
release points is the hysteresis (Bhys) of the device. This built-in
hysteresis allows clean switching of the output even in the pres-
ence of external mechanical vibration and electrical noise.
As used here, negative fl ux densities are defi ned as less than
zero (algebraic convention), i.e., -50 G is less than +10 G.
Applications. Allegro's pole-independent sensing technique
allows for operation with either a north pole or south pole mag-
net orientation, enhancing the manufacturability of the device.
The state-of-the-art technology provides the same output polarity
for either pole face.
It is strongly recommended that an external bypass ca pac i tor
be con nect ed (in close proximity to the Hall sensor) between the
supply and ground of the device to reduce both external noise
and noise generated by the chopper-sta bi li za tion tech nique. This
is especially true due to the relatively high im ped ance of battery
supplies.
The sim plest form of magnet that will op er ate these devices
is a bar magnet with either pole near the branded surface of the
device. Many oth er meth ods of operation are possible. Ex ten -
sive applications information for Hall-effect sensors is available
in:
• Hall-Effect IC Applications Guide, Application Note 27701;
• Hall-Effect Devices: Soldering, Gluing, Potting, En cap su -
lat ing, and Lead Forming, Application Note 27703.1;
• Soldering of Through-Hole Hall-Sensor Dervices, Application
Note 27703; and
• Soldering of Surface-Mount Hall-Sensor Devices, Application
Note 27703.2.
All are provided at
www.allegromicro.com
FUNCTIONAL DESCRIPTION (cont'd)
0+B
0
Dwg. GH-043-1
-B
OUTPUT ON
5 V
MAX BOPS
BRPS
BOPN
BRPN
OUTPUT VOLTAGE
MAGNETIC FLUX
OUTPUT OFF
OUTPUT
Dwg. EH-013-2
0.1 µF
SUPPLY
(3 V BATTERY)
10 pF
50 kΩ
X
V
DD
12
3
A3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8
SENSOR LOCATIONS
Package Designator 'LH'
Package Designator 'UA'
1 32
Dwg. MH-011-13
0.0195"
0.50 mm
NOM
BRANDED
SURFACE
ACTIVE AREA DEPTH
0.078"
1.98 mm
0.052"
1.32 mm
A
0.033"
0.84 mm
12
Dwg. MH-025-2
0.011"
0.28 mm
NOM
ACTIVE AREA DEPTH
0.056"
1.42 mm
A
3
Package Designator 'EH'
12
Dwg. MH-030
0.013"
0.34 mm
NOM
BRANDED
SURFACE
ACTIVE AREA DEPTH
0.035"
0.88 mm
0.062"
1.56 mm
A
3
654
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
www.allegromicro.com
9
PACKAGE DESIGNATOR ‘EH'
(Reference MO-229C WCED-1)
3.70
BSC
.146
1.25
BSC
.049
0.30
0.20
.012
.008
3.15
2.85
.124
.112
2.15
1.85
.085
.073
0.65
0.45
.026
.018
1.324
1.074
.052
.042
1.142
0.892
.045
.035
1.00
BSC
.039
0.50
BSC
.020
0.50
BSC
.020
0.95
BSC
.037
0.40
BSC
.016
0.25
BSC
.010
0.25
BSC
.010
0.30
BSC
.012
0.80
0.70
.031
.028
0.05
0.00
.002
.000
0.20
REF
.008
1
1
Dimensions in millimeters
U.S. Customary dimensions (in.) in brackets, for reference only
APin index area
BExposed thermal pad
Cø0.3 Thermal via (optional)
6
1
6
6
A
B
C
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
www.allegromicro.com
10
PACKAGE DESIGNATOR ‘LH’
(SOT23W, fi ts SC-59A solder-pad layout)
NOTES: 1. Tolerances on package height and width represent allowable mold offsets. Dimensions given are
measured at the widest point (parting line).
2. Exact body and lead configuration at vendor’s option within limits shown.
3. Height does not include mold gate flash.
4. Where no tolerance is specified, dimension is nominal.
Dimensions in Inches
(for reference only)
Dimensions in Millimeters
(controlling dimensions)
Dwg. MA-011-3 in
12
0.039
0.094
0.03
7
0.028
3
Dwg. MA-011-3 mm
12
1.00
2.40
0.95
0.70
3
Dwg. MA-010-3D in
12
0.006
0.000
0.0079
0.0050
0.083
0.073
0.118
0.106
0.037
BSC
0.022
REF
0.020
0.012
3
0.045
0.032
0°
TO
8° 0.010
MIN
GAUGE PLANE
SEATING PLANE
0.010
BSC
0.122
0.114
Dwg. MA-010-3D mm
12
0.15
0.00
0.20
0.127
2.10
1.85
3.00
2.70
0.95
BSC
0.55
REF
0.50
0.30
3
1.13
0.87
0°
TO
8° 0.25
MIN
GAUGE PLANE
SEATING PLANE
0.25
BSC
3.10
2.90
A3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
11
PACKAGE DESIGNATOR ‘UA’
Dimensions in Inches
(controlling dimensions)
Dimensions in Millimeters
(for reference only)
NOTES: 1. Tolerances on package height and width represent
allowable mold offsets. Dimensions given are measured
at the widest point (parting line).
2. Exact body and lead configuration at vendor’s option
within limits shown.
3. Height does not include mold gate flash.
4. Recommended minimum PWB hole diameter to clear
transition area is 0.035" (0.89 mm).
5. Where no tolerance is specified, dimension is nominal.
Dwg. MH-014E in
0.164
0.159
0.062
0.058
0.0173
0.0138
0.050
BSC
45°
0.640
0.600
0.0189
0.0142
0.085
MAX
45°
0.031
123
0.122
0.117
SEE NOTE
Dwg. MH-014E mm
4.17
4.04
1.57
1.47
0.44
0.35
1.27
BSC
45°
16.26
15.24
0.48
0.36
2.16
MAX
45°
0.79
123
3.10
2.97
SEE NOTE
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCH
www.allegromicro.com
12
The products described herein are man u fac tured under one or
more of the following U.S. pat ents: 5,045,920; 5,264,783; 5,442,283;
5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719;
5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pend-
ing.
Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such de par tures from the detail spec i fi ca tions as may be required
to permit improvements in the per for mance, reliability, or manufactur-
ability of its products. Before placing an order, the user is cautioned to
verify that the information being relied upon is current.
Allegro products are not authorized for use as critical components
in life-support ap pli anc es, devices, or systems without express written
approval.
The information included herein is believed to be accurate and reli-
able. However, Allegro MicroSystems, Inc. assumes no re spon si bil i ty
for its use; nor for any infringements of pat ents or other rights of third
parties that may result from its use.