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A3211 and A3212 Micropower, Ultra-sensitive Hall-effect Switches
Features and Benefits
Micropower operation Operation with north or south pole 2.5 to 3.5 V battery operation Chopper stabilized Superior temperature stability Extremely low switchpoint drift Insensitive to physical stress High ESD protection Solid-state reliability Small size Easily manufacturable with magnet pole independence
Description
The A 3211 and A3212 integrated circuits are ultra-sensitive, pole independent Hall-effect switches with latched digital output. These sensors are especially suited for operation in battery-operated, hand-held equipment such as cellular and cordless telephones, pagers, and palmtop computers. A 2.5 volt to 3.5 volt operation and a unique clocking scheme reduce the average operating power requirements to less than 15 W with a 2.75 volt supply. Unlike other Hall-effect switches, either a north or south pole of sufficient strength will turn the output on in the A3212, and in the absence of a magnetic field, the output is off. The A3211 provides an inverted output. The polarity independence and minimal power requirements allow these devices to easily replace reed switches for superior reliability and ease of manufacturing, 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 dependencies, and thermal stress.

Packages:
DFN/MLPD (EH)
DFN/MLPD (EL)
SIP (UA) SOT23W (LH) Not to scale
Continued on the next page...
Functional Block Diagram
SUPPLY
SWITCH
TIMING LOGIC
DYNAMIC OFFSET CANCELLATION
OUTPUT
SAMPLE & HOLD
LATCH
X
GROUND
Dwg. FH-020-5
3211-DS, Rev. 3
Conceptual Data Sheet Subject to Change Without Notice
March 24, 2006
A3211 and A3212
Description (continued) This device includes on a single silicon chip a Hall-voltage generator, small-signal amplifier, chopper stabilization, a latch, and a MOSFET output. Advanced 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. Four package styles provide magnetically op ti mized
Micropower, Ultrasensitive Hall Effect Switch
solutions for most ap pli ca tions. Miniature lowprofile surface-mount package types EH and EL (0.75 and 0.50 mm nominal height) are leadless, LH is a leaded lowprofile SMD, and UA is a three-lead SIP for through-hole mounting. Packages are available in lead (Pb) free versions (suffix, -T) with 100% matte tin plated leadframe. EL package for limited release, engineering samples available.
Selection Guide Part Number A3211EEHLT-T A3211EELLT-T A3211ELHLT-T A3212EEHLT-T A3212EELLT-T A3212ELHLT-T A3212EUA-T A3212LLHLT-T A3212LUA-T
1Pb-based
Pb-free1 Yes Yes Yes Yes Yes Yes Yes Yes Yes
Packing2 (Units/Pack) Tape and Reel (3000) Tape and Reel (3000) Tape and Reel (3000) Tape and Reel (3000) Tape and Reel (3000) Tape and Reel (3000) Bulk Pack (500) Tape and Reel (3000) Bulk Pack (500)
Package
Ambient Temperature TA (C) -40 to 85
Leadless Surface Mount 3-Pin Surface Mount Leadless Surface Mount 3-Pin Surface Mount SIP-3 Through Hole, Straight Lead 3-Pin Surface Mount SIP-3 Through Hole, Straight Lead
-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 variants 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 for A3212EEHLT and A3212EUA, and October 31, 2005 for A3212LLHLT and A3212LUA. 2Contact Allegro for additional packaging and handling options.
Absolute Maximum Ratings
Characteristic Supply Voltage Magnetic Flux Density Output Off Voltage Output Current Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Symbol VDD B VOUT IOUT TA TJ(max) Tstg Range E Range L Notes Rating 5 Unlimited 5 1 -40 to 85 -40 to 150 165 -65 to 170 Units V G V mA C C C C
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
2
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
Package Suffix `EL' Pinning
(Leadless Chip Carrier)
Package Suffix `EH' Pinning
(Leadless Chip Carrier)
NO CONNECTION
Dwg. PH-016-2
GROUND
SUPPLY
6 VDD
5
4
3
X
V
1
OUTPUT
DD
2
NO CONNECTION
3
GROUND
1
2
GROUND
Dwg. PH-016-1
Package Suffix `LH' Pinning
(SOT23W)
Package Suffix `UA' Pinning
(SIP)
3
X
V
DD
V
DD
1
2
1
2
3
GROUND
OUTPUT
SUPPLY
GROUND
Dwg. PH-016-1
Dwg. PH-016
Pinning is shown viewed from branded side.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
OUTPUT
SUPPLY
OUTPUT
SUPPLY
3
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
ELECTRICAL CHARACTERISTICS over operating voltage and temperature range (unless otherwise specified).
Characteristic Supply Voltage Range Output Leakage Current Output On Voltage Awake Time Period Duty Cycle Chopping Frequency Symbol VDD IOFF VOUT tawake tperiod d.c. fC IDD(EN) Supply Current IDD(DIS) IDD(AVG) Chip awake (enabled) Chip asleep (disabled) VDD = 2.75 V Test Conditions Operating VOUT = 3.5 V, Output off IOUT = 1 mA, VDD = 2.75 V Limits Min. 2.5 - - - - - - - - - - Typ.* 2.75 <1.0 100 45 45 0.1 340 - - 5.1 6.7 Max. 3.5 1.0 300 90 90 - - 2.0 8.0 10 10 Units V A mV s ms % kHz mA A A A
VDD = 3.5 V * Typical data is at TA = 25C and VDD = 2.75 V, and is for design information only.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
4
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
3211 MAGNETIC CHARACTERISTICS over operating voltage and temperature range (unless otherwise specified)
Characteristic Operate Points Release Points Hysteresis Symbol BOPS BOPN BRPS BRPN BHYS Test Conditions South pole to branded side; B > BOP, VOUT = High (Output Off) North pole to branded side; B > BOP, VOUT = High (Output Off) South pole to branded side; B < BRP, VOUT = Low (Output On) North pole to branded side; B < BRP, VOUT = Low (Output On) |BOPx - BRPx| Limits Min. - -55 10 - - Typ. 37 -40 31 -34 5.9 Max. 55 - - -10 - Units G G G G 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 off); BRPx = release point (output turns on). 3. Typical Data is at TA = +25C and VDD = 2.75 V and is for design information only. 4. 1 gauss (G) is exactly equal to 0.1 millitesla (mT).
3212 MAGNETIC CHARACTERISTICS over operating voltage and temperature range (unless otherwise specified)
Characteristic Operate Points Release Points Hysteresis Symbol BOPS BOPN BRPS BRPN BHYS Test Conditions South pole to branded side; B > BOP, VOUT = Low (Output On) North pole to branded side; B > BOP, VOUT = Low (Output On) South pole to branded side; B < BRP, VOUT = High (Output Off) North pole to branded side; B < BRP, VOUT = High (Output Off) |BOPx - BRPx| Limits Min. - -55 10 - - Typ. 37 -40 31 -34 5.9 Max. 55 - - -10 - Units G G G G 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 = +25C and VDD = 2.75 V and is for design information only. 4. 1 gauss (G) is exactly equal to 0.1 millitesla (mT).
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
5
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
TYPICAL OPERATING CHARACTERISTICS
SWITCH POINTS
60
60
40
BOPS BRPS
40
BOPS BRPS
SWITCH POINTS IN GAUSS
20
SWITCH POINTS IN GAUSS
20
0
VDD = 2.75 V
0
TA = 25C
-20 BRPN -40 BOPN
-20 BRPN -40 BOPN
-60 -50 -25 0 25 50 75 100 125 150
-60 2.4
2.6
2.8
3.0
3.2
3.4
3.6
Dwg. GH-057-2
AMBIENT TEMPERATURE IN C
Dwg. GH-027-3
SUPPLY VOLTAGE IN VOLTS
SUPPLY CURRENT
7.0
7.0
AVERAGE SUPPLY CURRENT IN A
6.0 VDD =3.5 V
AVERAGE SUPPLY CURRENT IN A
6.0
5.0
VDD =2.75 V
5.0
VDD =2.5 V 4.0
4.0
TA = 25C
3.0 -50
-25
0
25
50
75
100
125
150
3.0 2.4
2.6
2.8
3.0
3.2
3.4
3.6
Dwg. GH-058-7
AMBIENT TEMPERATURE IN C
Dwg. GH-028-11
SUPPLY VOLTAGE IN VOLTS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
6
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
FUNCTIONAL DESCRIPTION
Low Average Power. Internal timing circuitry activates the sensor for 45 s and deactivates it for the remainder of the period (45 ms). A short "awake" time allows for stabilization prior to the sensor sampling 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.
+V
B
PERIOD
IDD(EN)
"AWAKE" "SLEEP" SAMPLE & OUTPUT LATCHED
--
HALL VOLTAGE
IDD(DIS)
0
Dwg. WH-017-2
+
Dwg. AH-011-2
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 cancellation 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 dependencies, and thermal stress. The chopper-stabilizing technique cancels the mismatching of the resistor circuit by changing the direction of the current flowing through the Hall plate using CMOS switches and Hall voltage measurement taps, while maintaing the Hallvoltage signal that is induced by the external magnetic flux. 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 sampling 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 Amplifiers With A Trackand-Hold Signal Demodulator.
+V
SAMPLE & HOLD
X
Dwg. EH-012-1
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
7
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
FUNCTIONAL DESCRIPTION (cont'd)
Operation. The output of the A3212 switches low (turns on) when a magnetic field 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 field is reduced below the release point BRPS (or increased above BRPN), the device output switches high (turns off). The difference 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 presence of external mechanical vibration and electrical noise. The A3211 functions in the same manner, except the output voltage is reversed from the A3212, as shown in the figures to the right. As used here, negative flux densities are defined 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 magnet 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 capacitor be connected (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-stabilization technique. This is especially true due to the relatively high impedance of battery supplies. The simplest form of magnet that will operate these devices is a bar magnet with either pole near the branded surface of the device. Many other methods of operation are possible. Extensive applications information for Hall-effect sensors is available in: * Hall-Effect IC Applications Guide, Application Note 27701; * Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, 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
A3211
5V MAX
OUTPUT OFF BRPN B RPS
OUTPUT OFF
OUTPUT VOLTAGE
B OPN 0 -B
OUTPUT ON
B OPS
0
+B
MAGNETIC FLUX
A3212
5V MAX
OUTPUT OFF B OPN B OPS
OUTPUT VOLTAGE
OUTPUT ON 0 -B
BRPN
BRPS
OUTPUT ON +B
0
MAGNETIC FLUX
OUT P UT
2
DD
V
1
X
www.allegromicro.com
50 k
3
S UP P LY (3 V B AT T E R Y ) 0.1 F
Dwg. E H-013-2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
8
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
SENSOR LOCATIONS
Package Designator 'EH'
ACTIVE AREA DEPTH 0.013" 0.34 mm NOM 6 5 0.035" 0.88 mm 4 0.062" 1.56 mm
Package Designator 'EL'
ACTIVE AREA DEPTH 0.006" 0.16 mm NOM 3 .0406 1.03 mm
.0291 0.74 mm
BRANDED SURFACE
A
1 2 3
Dwg. MH-030
BRANDED SURFACE
A
1 2
Package Designator 'LH'
ACTIVE AREA DEPTH 0.011" 0.28 mm NOM 0.056" 1.42 mm 3
Package Designator 'UA'
ACTIVE AREA DEPTH 0.0195" 0.50 mm NOM
0.033" 0.84 mm
0.078" 1.98 mm 0.052" 1.32 mm
A
1 2
Dwg. MH-025-2
A
BRANDED SURFACE 1 2 3
Dwg. MH-011-13
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
9
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
PACKAGE DESIGNATOR `EH'
(Reference MO-229C WCED-1)
2.15 .085 1.85 .073 6
3.15 .124 2.85 .112 A 1
0.50 .020 BSC 0.30 .012 BSC 1.00 .039 BSC 3.70 .146 BSC 1.25 .049 BSC 0.25 .010 BSC 1 0.25 .010 BSC 0.40 .016 BSC 0.95 .037 BSC C 6
0.30 .012 0.20 .008 0.50 .020 BSC 1 0.65 .026 0.45 .018 1.324 .052 1.074 .042 B
0.80 .031 0.70 .028 0.20 .008 REF 0.05 .002 0.00 .000
6 1.142 .045 0.892 .035
Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only A Pin index area B Exposed thermal pad C o0.3 Thermal via (optional)
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
10
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
PACKAGE DESIGNATOR `EL'
MLPD 3 Contact
2.00 .079 BSC 3
2.00 .079 BSC A 1 2
1.350 .053 BSC 0.325 .013 REF 0.32 .013 MIN 1.025 .040 MAX 0.20 .008 REF D C 0.138 .005 REF 3
0.32 .013 0.20 .008 0.50 .020 BSC 0.50 .020 0.30 .012
0.55 .022 0.45 .018 0.15 .006 REF 0.05 .002 0.80 .031 0.00 .000 0.70 .028 1 2 0.138 .005 REF
Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only A Pin index area B Exposed thermal pad C Optional thermal vias, 0.30 [.012], pitch 1.2 [.047]
R0.200 .008 REF B
1.025 .040 0.775 .031
0.15 .006 MIN 1 0.40 .016 NOM
2.40 .094 REF 1.350 .053 1.100 .043
D Typical pad layout; adjust as necessary to meet application process requirements
3
0.50 .020 BSC
0.325 .013 REF
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
11
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
PACKAGE DESIGNATOR `LH'
(SOT23W, fits SC-59A solder-pad layout)
3.00 .118 2.70 .106 0.15 [.006] M C A B 3.04 .120 2.80 .110 A 8 0 0.20 .008 0.08 .003
3
B
2.10 .083 1.85 .073 Preliminary dimensions, for reference only Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only (reference JEDEC TO-236 AB, except case width and terminal tip-to-tip) Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Hall element (not to scale)
A
0.96 .038
A NOM
0.60 .024 0.25 .010
1
2 0.25 .010 SEATING PLANE 1.17 .046 0.75 .030 0.15 .006 0.00 .000 1.90 .075 C SEATING PLANE GAUGE PLANE
3X 0.10 [.004] C 3X 0.50 .020 0.30 .012 0.20 [.008] M C A B 0.95 .037
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
12
A3211 and A3212
Micropower, Ultrasensitive Hall Effect Switch
PACKAGE DESIGNATOR `UA'
.164 4.17 .159 4.04
.062 1.57 .058 1.47
C
.122 3.10 .117 2.97
B
.085 2.16 MAX
.031 0.79 REF A
.640 16.26 .600 15.24
.017 0.44 .014 0.35
1
2
3
.019 0.48 .014 0.36 .050 1.27 NOM Dimensions in inches Metric dimensions (mm) in brackets, for reference only A Dambar removal protrusion (6X)
B Ejector mark on opposite side C Hall element (not to scale)
The products described herein are manufactured under one or more of the following U.S. patents: 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 pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability 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 appliances, devices, or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties that may result from its use.
Copyright (c) 2002, 2006 Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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