Allegro A3291 Chopper stabilized, precision hall effect latches for consumer and industrial application Datasheet

A3290 and A3291
Chopper Stabilized, Precision Hall Effect Latches for
Consumer and Industrial Applications
Features and Benefits
Description
▪ Symmetrical switchpoints
▪ Resistant to physical stress
▪ Superior temperature stability
▪ Output short-circuit protection
▪ Operation from unregulated supply
▪ Reverse battery protection
▪ Solid-state reliability
▪ Small package size
The A3290 and A3291 Hall effect latches are extremely
temperature-stable and stress-resistant sensor ICs, especially
suited for operation over extended temperature ranges (up
to 125°C). Superior high-temperature performance is made
possible through Dynamic Offset Cancellation, which reduces
the residual offset voltage normally caused by device package
overmolding, temperature dependencies, and thermal stress. The
two devices are identical except for their magnetic switchpoints.
They are not intended for automotive applications.
Both devices include, on a single silicon chip, a voltage regulator,
a Hall-voltage generator, a small-signal amplifier, chopper
stabilization, a Schmitt trigger, and a short-circuit protected
open-drain output to sink up to 25 mA. A south polarity magnetic
field of sufficient strength is required to turn the output on. A
north polarity field of sufficient strength is necessary to turn
the output off. An onboard regulator permits operation with
supply voltages in the range of 4.2 to 24 V.
Packages:
3-pin SOT23W (suffix LH)
3-pin SIP (suffix UA)
Two package styles provide a magnetically optimized package
for most applications. Type LH is a miniature SOT23W lowprofile surface-mount package, and type UA is a three-pin
ultramini SIP for through-hole mounting. Both packages are
lead (Pb) free with 100% matte tin leadframe plating.
Not to scale
Functional Block Diagram
VCC
Regulator
Amp
Sample and Hold
Dynamic Offset
Cancellation
OUT
Low-Pass
Filter
Control
Current Limit
17
GND
A3290-DS, Rev. 9
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
A3290 and
A3291
Selection Guide
Magnetic Switchpoints*
Packing1
Part Number
Package Type
Operate, BOP Release, BRP
(G)
(G)
A3290KLHLT-T
3000 pieces per 7-in. reel
Surface mount SOT23W
A3290KUA-T
500 pieces per bulk bag
Through hole ultramini SIP
A3291KLHLT-T
3000 pieces per 7-in. reel
Surface mount SOT23W
A3291KUA-T
500 pieces per bulk bag
Through hole ultramini SIP
*Algebraic
5 to 50
–50 to –5
10 to 100
–100 to –10
convention used: (+) south polarity, (–) north polarity.
Absolute Maximum Ratings
Rating
Units
Supply Voltage
Characteristic
Symbol
VCC
26.5
V
Reverse Battery Voltage
VRCC
–30
V
Output Off Voltage
VOUT
26
V
Continuous Output Current
IOUT
25
mA
Reverse Output Current
IROUT
–50
mA
Magnetic Flux Density
B
Operating Ambient Temperature
TA
Maximum Junction Temperature
Notes
Device provides internal current limiting to help
protect itself from output short circuits
Unlimited
G
–40 to 125
ºC
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Storage Temperature
Range K
Pin-out Diagrams
Terminal List
3
Name
PTCT
PTCT
1
2
1
Package LH
2
VCC
OUT
GND
LH
1
2
3
Number
UA
1
3
2
Function
Power supply
Output
Ground
3
Package UA
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A3290 and
A3291
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
ELECTRICAL CHARACTERISTICS over operating temperature range, unless otherwise noted
Characteristic
Symbol
Test Conditions
Supply Voltage Range2
VCC
Operating, TJ < 165°C
Output Leakage Current
IOFF
VOUT = 24 V, B < BRP
Output Saturation Voltage
VOUT(SAT)
IOUT = 20 mA, B > BOP
Output Current Limit
ION
B > BOP
Power-On Time
tPO
VCC > 4.2 V
Chopping Frequency
fC
RLOAD = 820 Ω, CLOAD = 20 pF
Output Rise Time
tR
Output Fall Time
tF
RLOAD = 820 Ω, CLOAD = 20 pF
B < BRP , VCC = 12 V
Supply Current
ICC
B > BOP , VCC = 12 V
Reverse Battery Current
IRCC
VRCC = –30 V
Zener Voltage
VZ + VD
ICC = 15 mA, TA = 25°C
Zener Impedance
ZZ + ZD
ICC = 15 mA, TA = 25°C
1Typical
Min.
4.2
–
–
30
–
–
–
–
–
–
–
28
–
Typ.1
–
–
185
–
–
800
0.2
0.1
3.0
4.0
–
–
50
Max
24
10
500
60
50
–
2.0
2.0
8.0
8.0
–5.0
–
–
Units
V
μA
mV
mA
μs
kHz
μs
μs
mA
mA
mA
V
Ω
data at TA = 25°C, 12 V.
VCC must be derated for power dissipation and junction temperature. See application information.
2Maximum
MAGNETIC CHARACTERISTICS1 over VCC range, unless otherwise noted
Characteristic
Symbol
A3290
Operate Point2
BOP
A3291
A3290
Release Point3
BRP
A3291
A3290
Hysteresis (BOP – BRP)
BHYS
A3291
Test Conditions
TA = 25°C and TA(max)
Min.
Max.
Units
5
50
G
TA = –40°C
5
50
G
TA = 25°C and TA(max)
10
100
G
TA = –40°C
10
100
G
TA = 25°C and TA(max)
–50
–5
G
TA = –40°C
–50
–5
G
TA = 25°C and TA(max)
–100
–10
G
TA = –40°C
–100
–10
G
10
100
G
TA = 25°C and TA(max)
TA = –40°C
–
100
G
TA = 25°C and TA(max)
20
200
G
TA = –40°C
–
200
G
1The
positive polarity symbol (+) indicates south magnetic field, and the negative polarity symbol (–) indicates north magnetic field.
2Required polarity observed and transition of magnetic gradient through B . See functional description.
OP
3Required polarity observed and transition of magnetic gradient through B after B . See functional description.
RP
OP
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A3290 and
A3291
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
RθJA
Package Thermal Resistance
Test Conditions*
Value Units
Package LH, 1-layer PCB with copper limited to solder pads
228
ºC/W
Package LH, 2-layer PCB with 0.463 in.2 of copper area each side
connected by thermal vias
110
ºC/W
Package UA, 1-layer PCB with copper limited to solder pads
165
ºC/W
*Additional thermal information available on Allegro website.
Maximum Allowable VCC (V)
Power Derating Curve
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
VCC(max)
2-layer PCB, Package LH
(RQJA = 110 ºC/W)
1-layer PCB, Package UA
(RQJA = 165 ºC/W)
1-layer PCB, Package LH
(RQJA = 228 ºC/W)
20
40
60
80
100
120
VCC(min)
140
160
180
Temperature (ºC)
Power Dissipation, PD (m W)
Power Dissipation versus Ambient Temperature
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
2l
(R aye
rP
θJ
C
A =
11 B, P
0 º ac
1-la
C/ ka
W
(R yer PC
) ge L
θJA =
B
H
165 , Pac
ºC/ kage
W)
UA
1-lay
er P
(R
CB,
θJA =
228 Packag
ºC/W
e LH
)
20
40
60
80
100
120
Temperature (°C)
140
160
180
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
A3290 and
A3291
Functional Description
Chopper-Stabilized Technique
The Hall element can be considered as a resistor array similar
to a Wheatstone bridge. A basic circuit is shown in figure 1,
demonstrating the effect of the magnetic field flux density, B,
impinging on the Hall element. When using Hall effect technology, a limiting factor for switchpoint accuracy is the small
signal voltage, VHALL, developed across the Hall element. This
voltage is disproportionally small relative to the offset that can
be produced at the output of the Hall device, caused by device
overmolding, temperature dependencies, and thermal stress.
A large portion of the offset is a result of the mismatching of
these resistors. The A3290 and A3291 use a proprietary dynamic
offset cancellation technique, with an internal high-frequency
clock, to reduce the ressidual offset. The chopper-stabilizing
B
+VHALL
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. This technique will also
slightly degrade the device output repeatability. A relatively high
sampling frequency is used in order to process faster signals.
More detailed descriptions of the circuit operation can be found
on the Allegro Web site, including: Technical Paper STP 97-10,
Monolithic Magnetic Hall Sensing Using Dynamic Quadrature
Offset Cancellation, and Technical Paper STP 99-1, ChopperStabilized Amplifiers with a Track-and-Hold Signal Demodulator.
Operation
The outputs of the A3290 and A3291 switch low (turn on) when
a magnetic field perpendicular to the Hall element transitions
through and exceeds the Operate Point threshold, BOP. This is
illustrated in figure 3. After turn-on, the output is capable of
sinking 25 mA, and the output voltage reaches VOUT(SAT).
Figure 1. Hall element, basic circuit operation
Regulator
VOUT(on)(sat)
BOP
BRP
LowPass
Filter
VOUT(off)
Switch to Low
Amp
Sample and Hold
V+
Hysteresis of ΔVOUT
Switching Due to ΔB
Switch to High
–V HALL
VOUT
+V CC
technique cancels the mismatching of the resistor circuit by
changing the direction of the current flowing through the Hall
element. To do so, CMOS switches and Hall voltage measurement taps are used, while maintaining VHALL signal that is
induced by the external magnetic flux.
B+
BHYS
Figure 2. Chopper stabilization circuit (dynamic quadrature offset
cancellation)
Figure 3. Output voltage responds to sensed magnetic flux density.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
A3290 and
A3291
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
Note that these devices latch; that is, after a south (+) polarity
magnetic field of sufficient strength impinging on the branded
face of the device turns on the device, the device remains on until
the magnetic field is reduced below the Release Point threshold,
BRP . At that transition, the device output goes 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.
When the devices are powered on, if the ambient magnetic field
has an intensity that is between BOP and BRP , the initial output
state is indeterminate. The first time that the level of B either
rises through BOP , or falls through BRP , however, the correct
output state is obatined.
Application Information
It is strongly recommended that an external bypass capacitor be
connected (in close proximity to the Hall element) between the
supply and ground of the device to reduce both external noise
and noise generated by the chopper-stabilization technique. This
configuration is shown in figure 4.
The simplest form of magnet that will operate these devices is a
ring magnet.Other methods of operation, such as linear magnets,
are possible.
The device must be operated below the maximum junction
temperature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied
power or improving the heat dissipation properties of the application. The Package Thermal Resistance, RJA, is a figure of merit
summarizing the ability of the application and the device to dissi-
pate heat from the junction (die), through all paths to the ambient
air. Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, RJC, is
relatively small component of RJA. Ambient air temperature,
TA, and air motion are significant external factors, damped by
overmolding. Sample power dissipation results are given in the
Thermal Characteristics section. Additional thermal data is also
available on the Allegro website.
Extensive applications information for Hall-effect devices is
available in: Hall-Effect IC Applications Guide, Application Note
27701 and Guidelines for Designing Subassemblies Using HallEffect Devices, Application Note 27703.1
VCC
VCC
A329x
VOUT
0.1 uF
GND
Figure 4. Typical basic application circuit. A bypass capacitor is highly
recommended.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
A3290 and
A3291
Package LH, 3-Pin SOT23W
+0.12
2.98 –0.08
1.49 D
4°±4°
3
A
+0.020
0.180–0.053
0.96 D
+0.10
2.90 –0.20
+0.19
1.91 –0.06
2.40
0.70
D
0.25 MIN
1.00
2
1
0.55 REF
0.25 BSC
0.95
Seating Plane
Gauge Plane
8X 10° REF
B
PCB Layout Reference View
Branded Face
1.00 ±0.13
C
Standard Branding Reference View
+0.10
0.05 –0.05
0.95 BSC
NNT
0.40 ±0.10
1
For Reference Only; not for tooling use (reference dwg. 802840)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A
Active Area Depth, 0.28 mm REF
B
Reference land pattern layout
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances
C
Branding scale and appearance at supplier discretion
D
Hall element, not to scale
N = Last two digits of device part number
T = Temperature code (letter)
NNN
1
N = Last three digits of device part number
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
A3290 and
A3291
Package UA, 3-Pin SIP
+0.08
4.09 –0.05
45°
B
C
E
2.06
1.52 ±0.05
1.45 E
Mold Ejector
Pin Indent
+0.08
3.02 –0.05
E
2.16
MAX
Branded
Face
45°
1
D Standard Branding Reference View
0.79 REF
= Supplier emblem
N = Last two digits of device part number
T = Temperature code
A
0.51
REF
1
2
NNT
3
+0.03
0.41 –0.06
15.75 ±0.51
For Reference Only; not for tooling use (reference DWG-9049)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A
Dambar removal protrusion (6X)
B Gate burr area
C Active Area Depth, 0.50 mm REF
+0.05
0.43 –0.07
D
Branding scale and appearance at supplier discretion
E
Hall element, not to scale
1.27 NOM
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
Chopper Stabilized, Precision Hall Effect Latches
for Consumer and Industrial Applications
A3290 and
A3291
Revision History
Revision
Revision Date
Description of Revision
Rev. 9
May 24, 2012
Update LH package branding
Copyright ©2005-2012, Allegro MicroSystems, Inc.
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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use;
nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9