3212
Preliminary Information
(Subject to change without notice)
November 12, 2001
Package Suffix ‘LH’ Pinning
3
MICROPOWER, ULTRA-SENSITIVE
HALL-EFFECT SWITCH
The A3212 integrated circuit is an ultra-sensitive, pole independent Hall-
effect switch with a latched digital output. This sensor is 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
µW
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 absence of a magnetic field, 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
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.
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.
The A3212Ex is rated for operation over a temperature range of -40
°
C to
85
°
C. The A3212Lx is rated for operation over a temperature range of -40
°
C to
150
°
C. Two package styles provide a magnetically optimized package for most
applications. Suffix ‘LH’ is a miniature low-profile surface-mount package
while suffix ‘UA’ is a three-lead ultra-mini-SIP for through-hole or surface
mounting.
Data Sheet
27622.61*
V
DD
1
X
2
GROUND
Dwg. PH-016-1
Pinning is shown viewed from branded side.
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25
°
C
Supply Voltage, V
DD
.............................
5 V
Magnetic Flux Density, B ..........
Unlimited
Output Off Voltage, V
OUT
.....................
5 V
Output Current, I
OUT
..........................
1 mA
Junction Temperature, T
J
...............
+170
°
C
Operating Temperature Range, T
A
Suffix
‘E’
....................
-40
°
C to +85
°
C
Suffix
‘L’
..................
-40
°
C to +150
°
C
Storage Temperature Range,
T
S
..............................
-65
°
C to +170
°
C
Caution: These CMOS devices have input
static protection (Class 3) but are still
susceptible to damage if exposed to
extremely high static electrical charges.
OUTPUT
SUPPLY
FEATURES
s
s
s
s
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
Solid-State Reliability
Small Size
Easily Manufacturable With Magnet Pole Independence
s
s
s
s
Always order by complete part number: the prefix ‘A’ + the basic four-digit
part number + the suffix ‘E’ or ‘L’ to indicate operating temperature range + a
suffix to indicate package style, e.g.,
A3212ELH .
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCHES
FUNCTIONAL BLOCK DIAGRAM
SUPPLY
SWITCH
TIMING
LOGIC
DYNAMIC
OFFSET CANCELLATION
OUTPUT
SAMPLE
& HOLD
LATCH
X
GROUND
Dwg. FH-020-5
Package Suffix ‘UA’ Pinning
700
ALLOWABLE PACKAGE POWER DISSIPATION in MILLIWATTS
600
Suffix "UA"
R
θJA
= 206°C/W
500
400
V
Suffix "LH"
R
θJA
= 248°C/W
DD
300
1
X
2
3
200
GROUND
100
0
20
40
60
100
80
120
AMBIENT TEMPERATURE in
°C
140
160
180
Dwg. GH-046-3A
Dwg. PH-016
Pinning is shown viewed from branded side.
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 2001, Allegro MicroSystems, Inc.
OUTPUT
SUPPLY
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCHES
ELECTRICAL CHARACTERISTICS over operating voltage and temperature range (unless
otherwise specified).
Limits
Characteristic
Supply Voltage Range
Output Leakage Current
Output On Voltage
Awake Time
Period
Duty Cycle
Chopping Frequency
Supply Current
(2.5
≤
V
DD
≤3.5
V)
Symbol
V
DD
I
OFF
V
OUT
t
awake
t
period
d.c.
f
C
I
DD(EN)
I
DD(DIS)
I
DD(AVG)
Chip awake (enabled)
Chip asleep (disabled)
V
DD
= 2.75 V
V
DD
= 3.5 V
Test Conditions
Operating
1
V
OUT
= 3.5 V, B
RPN
< B < B
RPS
I
OUT
= 1 mA, V
DD
= 2.75 V
Min.
2.5
—
—
—
—
—
—
—
—
—
—
Typ.
2.75
˙1.0
100
45
45
0.1
340
—
—
4.2
4.9
Max.
3.5
1.0
300
90
90
—
—
2
8
10
10
Units
V
µA
mV
µs
ms
%
kHz
mA
µA
µA
µA
NOTES: 1. Operate and release points will vary with supply voltage.
2. B
OPx
= operate point (output turns ON); B
RPx
= release point (output turns OFF).
3. Typical Data is at T
A
= +25°C and V
DD
= 2.75 V and is for design information only.
MAGNETIC CHARACTERISTICS over operating voltage and temperature range (unless
otherwise specified).
Limits
Characteristic
Operate Points
Symbol
B
OPS
B
OPN
Release Points
B
RPS
B
RPN
Hysteresis
B
hys
Test Conditions
South pole to branded side
North pole to branded side
South pole to branded side
North pole to branded side
|B
OPx
- B
RPx
|
Min.
—
-55
10
—
—
Typ.
—
—
—
—
8
Max.
55
—
—
-10
—
Units
G
G
G
G
G
NOTES: 1. As used here, negative flux densities are defined as less than zero (algebraic convention) and -50 G is less than +10 G.
2. Typical Data is at T
A
= +25°C and V
DD
= 2.75 V and is for design information only.
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3
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCHES
CRITERIA FOR DEVICE QUALIFICATION
All Allegro sensors are subjected to stringent qualification requirements prior to being released to production.
To become qualified, except for the destructive ESD tests, no failures are permitted.
Qualification Test
Biased Humidity (HAST)
High-Temperature
Operating Life (HTOL)
Accelerated HTOL
Test Method and Test Conditions
T
A
= 130°C, RH = 85%
JESD22-A108,
T
A
= 150°C, T
J
≤
165°C
T
A
= 175°C, T
J
≤
190°C
Test Length
50 hrs
408 hrs
Samples
77
77
Comments
V
DD
= V
OUT
= 3 V
V
DD
= V
OUT
= 3 V
504 hrs
77
V
DD
= V
OUT
= 3 V
Autoclave, Unbiased
JESD22-A102, Condition C,
T
A
= 121°C, 15 psig
MIL-STD-883, Method 1008,
T
A
= 170°C
MIL-STD-883, Method 1010,
-65°C to +150°C
96 hrs
77
High-Temperature
(Bake) Storage Life
Temperature Cycle
1000 hrs
77
500 cycles
77
Latch-Up
Pre/Post
Reading
Pre/Post
Reading
CDF-AEC-Q100-002
Pre/Post
Reading
Pre/Post
Reading
6
Electro-Thermally
Induced Gate Leakage
ESD,
Human Body Model
ESD,
Machine Model
Electrical Distributions
6
3 per
test
3 per
test
30
Test to failure,
All leads > 5 kV
Test to failure,
All leads > 350 V
JESD22-A115
Per Specification
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
3212
MICROPOWER,
ULTRA-SENSITIVE
HALL-EFFECT SWITCHES
FUNCTIONAL DESCRIPTION
Low Average Power.
Internal timing circuitry activates the
sensor for 45
µs
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.
PERIOD
"AWAKE"
+V
SAMPLE
& HOLD
X
I
DD(EN)
"SLEEP"
SAMPLE &
OUTPUT LATCHED
Dwg. EH-012-1
I
DD(DIS)
0
Dwg. WH-017-2
B
+V
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 dependen-
cies, 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 Hall-voltage 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 Track-and-Hold Signal Demodulator.
—
HALL
VOLTAGE
+
Dwg. AH-011-2
Operation.
The output of this device switches low (turns on)
when a magnetic field perpendicular to the Hall sensor exceeds
the operate point B
OPS
(or is less than B
OPN
). After turn-on, the
output is capable of sinking up to 1 mA and the output voltage
is V
OUT(ON)
. When the magnetic field is reduced below the
release point B
RPS
(or increased above B
RPN
), the device output
switches high (turns off). The difference in the magnetic
operate and release points is the hysteresis (B
hys
) of the device.
This built-in hysteresis allows clean switching of the output
even in the presence of external mechanical vibration and
electrical noise.
As used here, negative flux densities are defined as less
than zero (algebraic convention) and -50 G is less than +10 G.
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5
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