A1145 and A1146: Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches

A1145 and A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: October 31, 2011
• for the A1145EUA-T use the A1155LUA-T
• for the A1146EUA-T and the A1146LUA-T use the A1156LUA-T
• for the A1145ELHLT-T use the A1155LLHLX-T
• for the A1146ELHLT-T and the A1146LLHLT-T use the A1156LLHLX-T
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. 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 which may result from its use.
A1145 and A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Features and Benefits
Description
▪ Chopper stabilization
▫ Low switchpoint drift over operating
temperature range
▫ Low sensitivity to stress
▪ Factory programmed at end-of-line for optimized
switchpoints
▪ On-chip protection
▫ Supply transient protection
▫ Reverse-battery protection
▫ On-board voltage regulator
▫ 3.5 to 24 V operation
The A1145 and A1146 devices are two-wire, unipolar, Hall
effect switches that are factory-programmed at end-of-line to
optimize ultrasensitive magnetic switchpoint accuracy. These
devices use a patented high frequency chopper-stabilization
technique, produced using the Allegro advanced BiCMOS
wafer fabrication process, to achieve magnetic stability and
to eliminate offset inherent in single-element devices exposed
to harsh application environments.
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
Commonly found in a number of automotive applications,
these switches are utilized in sensing seat track position, seat
belt buckle presence, hood/trunk latching, and shift selector
position. Two-wire unipolar switches, such as the A1145
and A1146, are particularly advantageous in price-sensitive
applications because they require one less wire for operation
than do switches with the more traditional open-collector output.
Additionally, the system designer inherently gains diagnostics
because there is always output current flowing, which should
be in either of two narrow ranges. Any current level not within
these ranges indicates a fault condition. These devices also
Continued on the next page…
Not to scale
Functional Block Diagram
V+
VCC
Regulator
To All Subcircuits
Dynamic Offset
Cancellation
0.01 uF
Amp
Sample and Hold
Clock/Logic
Low-Pass
Filter
GND
Package UA Only
A1145-DS, Rev. 16
GND
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Description (continued)
feature on-chip transient protection and a Zener clamp to protect
against overvoltage conditions on the supply line.
The output currents of the A1146 switches HIGH in the presence
of a south (+) polarity magnetic field of sufficient strength, and
switches LOW otherwise, as in the presence of a weak field or a
north (–) polarity field. The A1145 has an opposite output: the
currents switch LOW in the presence of a south-polarity magnetic
field of sufficient strength, and switch HIGH otherwise.
Both versions are offered in two package styles. The LH is a SOT23W, miniature low-profile package for surface-mount applications.
The UA is a three-lead ultramini SIP for through-hole mounting.
Each package is available in a lead (Pb) free version (suffix, –T)
with 100% matte tin plated leadframe. Field-programmable versions
also available: A1185 and A1186.
Selection Guide
Packing1
Part Number
Package
A1145ELHLT-T3
Tape and Reel, 3000 pieces/reel
Surface Mount
A1145EUA-T4
Bulk Bag, 500 pieces/bag
Through Hole
A1146ELHLT-T3
Tape and Reel, 3000 pieces/reel
Surface Mount
A1146EUA-T4
Bulk Bag, 500 pieces/bag
Through Hole
A1146LLHLT-T3
Tape and Reel, 3000 pieces/reel
Surface Mount
A1146LUA-T4
Bulk Bag, 500 pieces/bag
Through Hole
Operating Ambient
Temperature, TA
(°C)
Output Level in
South (+) Field2
–40 to 85
Low
–40 to 85
High
–40 to 150
1Contact Allegro
for additional packing options.
(+) magnetic fields must be of sufficient strength.
3This variant is in production, however, it has been deemed Pre-End of Life. The product is approaching end of life. Within a minimum of
6 months, the device will enter its final, Last Time Buy, order phase. Status change: January 31, 2011. Suggested replacements: for the
A1145ELHLT-T use the A1155LLHLX-T, for the A1146ELHLT-T and the A1146LLHLT-T use the A1156LLHLX-T.
4Variant is in production but has been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of the variant is
currently restricted to existing customer applications. The variant should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: January 31, 2011.
2South
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
Supply Voltage
VCC
28
V
Reverse Supply Voltage
VRCC
–18
V
Magnetic Flux Density
B
Unlimited
G
Range E
–40 to 85
ºC
Range L
Operating Ambient Temperature
TA
–40 to 150
ºC
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Storage Temperature
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
ELECTRICAL CHARACTERISTICS over the operating voltage and temperature ranges, unless otherwise specified
Characteristic
Supply Voltage1
Supply Current2
Reverse Supply Current
Symbol
Test Conditions
VCC
Min.
Typ.
Max.
Units
3.5
–
24
V
ICCL
B > BOP for A1145; B < BRP for A1146
5
–
6.9
mA
ICCH
B > BOP for A1146; B < BRP for A1145
12
–
17
mA
IRCC
VRCC = –18 V
–
–
–1.6
mA
Supply Zener Clamp Voltage
VZSUPPLY
ICC = ICCL(max) + 3 mA; TA = 25°C
28
–
40
V
Supply Zener Clamp Current3
IZSUPPLY
VZSUPPLY = 28 V
–
–
9.9
mA
Capacitance of the oscilloscope performing
the measurement = 20 pF
–
36
–
mA/μs
–
200
–
kHz
CBYPASS = 0.01 μF
–
–
25
μs
t < ton; VCC slew rate > 25 mV/μs
–
HIGH
–
–
Output Slew Rate4
di/dt
Chopping Frequency
fC
Power-On Time5
ton
Power-On State6,7
POS
1V
CC represents
2Relative values
the generated voltage between the VCC pin and the GND pin.
of B use the algebraic convention, where positive values indicate south magnetic polarity, and negative values indicate north magnetic
polarity; therefore greater B values indicate a stronger south polarity field (or a weaker north polarity field, if present).
3I
ZSUPPLY(max) = ICCL(max) + 3 mA.
4Measured without bypass capacitor between VCC and GND. Use of a bypass capacitor results in slower current change.
5Measured with and without bypass capacitor of 0.01 μF. Adding a larger bypass capacitor causes longer Power-On Time.
6POS is defined as true only with a V
CC slew rate of 25 mV / μs or greater. Operation with a VCC slew rate less than 25 mV / μs can permanently harm
device performance.
7POS is undefined for t > t or B
on
RP < B < BOP .
MAGNETIC CHARACTERISTICS over the operating voltage and temperature ranges, unless otherwise specified
Characteristic
Symbol
Operate Point
BOP
Release Point
BRP
Hysteresis
BHYS
Test Conditions
A1145
ICC = ICCL
A1146
ICC = ICCH
A1145
ICC = ICCH
A1146
ICC = ICCL
BHYS = BOP – BRP
Min.
Typ.*
Max.
Units
20
37
60
G
10
22
55
G
5
15
30
G
*Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions, such as TA = 25°C and VCC = 12 V.
Performance may vary for individual units, within the specified maximum and minimum limits.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Characteristic Data
Supply Current (Low) versus Ambient Temperature
at Various Levels of VCC
(A1145 and A1146)
Supply Current (High) versus Ambient Temperature
at Various Levels of VCC
(A1145 and A1146)
20
10
18
8
6
3.5 V
12.0 V
24.0 V
4
VCC
ICCH (mA)
ICCL (mA)
VCC
3.5 V
12.0 V
24.0 V
14
12
2
0
–50
16
0
50
100
150
10
–50
200
0
Ambient Temperature, TA (°C)
Operate Point versus Ambient Temperature
at Various Levels of VCC
(A1145 and A1146)
40
60
35
40
3.5 V
12.0 V
24.0 V
30
5
Ambient Temperature, TA (°C)
200
3.5 V
12.0 V
24.0 V
15
10
150
VCC
20
10
100
200
25
20
50
150
30
VCC
BHYS (G)
BOP (G)
50
0
100
Switchpoint Hysteresis versus Ambient Temperature
at Various Levels of VCC
(A1145 and A1146)
70
0
–50
50
Ambient Temperature, TA (°C)
0
–50
0
50
100
150
200
Ambient Temperature, TA (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
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 Web site.
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
(RθJA = 110 ºC/W)
1-layer PCB, Package UA
(RθJA = 165 ºC/W)
1-layer PCB, Package LH
(RθJA = 228 ºC/W)
20
40
60
80
100
VCC(min)
120
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
5
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Functional Description
Operation
BRP
BHYS
(A) A1145
B+
0
ICC(L)
B–
BRP
BOP
B–
ICC(H)
ICC
ICC
ICC(L)
0
I+
Switch to Low
Switch to Low
Switch to High
ICC(H)
Switch to High
I+
allows clean switching of the output even in the presence of
external mechanical vibration and electrical noise. The A1146
device switches with opposite polarity for similar BOP and BRP
values, in comparison to the A1145 (see figure 1).
BOP
The output, ICC, of the A1145 device switches low after the
magnetic field at the Hall element exceeds the operate point
threshold, BOP. When the magnetic field is reduced to below the
release point threshold, BRP, the device output goes high. The
differences between the magnetic operate and release point is
called the hysteresis of the device, BHYS. This built-in hysteresis
B+
BHYS
(B) A1146
Figure 1. Alternative switching behaviors are available in the A114x device family. On the horizontal axis, the B+ direction indicates
increasing south polarity magnetic field strength, and the B– direction indicates decreasing south polarity field strength (including the
case of increasing north polarity).
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Chopper Stabilization Technique
When using Hall-effect technology, a limiting factor for
switchpoint accuracy is the small signal voltage developed
across the Hall element. This voltage is disproportionally small
relative to the offset that can be produced at the output of the
Hall element. This makes it difficult to process the signal while
maintaining an accurate, reliable output over the specified operating temperature and voltage ranges.
Chopper stabilization is a unique approach used to minimize
Hall offset on the chip. The patented Allegro technique, namely
Dynamic Quadrature Offset Cancellation, removes key sources
of the output drift induced by thermal and mechanical stresses.
This offset reduction technique is based on a signal modulationdemodulation process. The undesired offset signal is separated
from the magnetic field-induced signal in the frequency domain,
through modulation. The subsequent demodulation acts as a
modulation process for the offset, causing the magnetic fieldinduced signal to recover its original spectrum at baseband, while
the DC offset becomes a high-frequency signal. The magneticsourced signal then can pass through a low-pass filter, while
the modulated DC offset is suppressed. This configuration is
illustrated in figure 2.
The chopper stabilization technique uses a 200 kHz high
frequency clock. For demodulation process, a sample and hold
technique is used, where the sampling is performed at twice the
chopper frequency (400 kHz). This high-frequency operation
allows a greater sampling rate, which results in higher accuracy
and faster signal-processing capability. This approach desensitizes the chip to the effects of thermal and mechanical stresses,
and produces devices that have extremely stable quiescent Hall
output voltages and precise recoverability after temperature
cycling. This technique is made possible through the use of a
BiCMOS process, which allows the use of low-offset, low-noise
amplifiers in combination with high-density logic integration
and sample-and-hold circuits.
The repeatability of magnetic field-induced switching is affected
slightly by a chopper technique. However, the Allegro highfrequency chopping approach minimizes the affect of jitter and
makes it imperceptible in most applications. Applications that
are more likely to be sensitive to such degradation are those
requiring precise sensing of alternating magnetic fields; for
example, speed sensing of ring-magnet targets. For such applications, Allegro recommends its digital device families with lower
sensitivity to jitter. For more information on those devices,
contact your Allegro sales representative.
Regulator
Hall Element
Amp
Sample and
Hold
Clock/Logic
Low-Pass
Filter
Figure 2. Chopper stabilization circuit (Dynamic Quadrature Offset Cancellation)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
A1145 and
A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Application Information
Typical Application Circuit
The A114x family of devices must be protected by an external
bypass capacitor, CBYP, connected between the supply, VCC,
and the ground, GND, of the device. CBYP reduces both external
noise and the noise generated by the chopper-stabilization function. As shown in figure 3, a 0.01 μF capacitor is typical.
V+
VCC
A114x
Installation of CBYP must ensure that the traces that connect it to
the A114x pins are no greater than 5 mm in length.
All high-frequency interferences conducted along the supply
lines are passed directly to the load through CBYP, and it serves
only to protect the A114x internal circuitry. As a result, the load
ECU (electronic control unit) must have sufficient protection,
other than CBYP, installed in parallel with the A114x.
GND
CBYP
0.01 μF
GND
B
A
A series resistor on the supply side, RS (not shown), in combination with CBYP, creates a filter for EMI pulses.
When determining the minimum VCC requirement of the A114x
device, the voltage drops across RS and the ECU sense resistor,
RSENSE, must be taken into consideration. The typical value for
RSENSE is approximately 100 Ω.
B
A
Package UA Only
B
Maximum separation 5 mm
RSENSE
ECU
Figure 3. Typical application circuit
For additional general application information, visit the Allegro
Web site at www. allegromicro.com.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
A1145 and
A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Power Derating
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. This section presents a procedure for correlating
factors affecting operating TJ. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, RJA, is a figure of merit summarizing the ability of the application and the device to dissipate
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.
The effect of varying power levels (Power Dissipation, PD), can
be estimated. The following formulas represent the fundamental
relationships used to estimate TJ, at PD.
PD = VIN × IIN

(1)
T = PD × RJA (2)
TJ = TA + ΔT
Example: Reliability for VCC at TA = 150°C, package UA, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
RJA = 165°C/W, TJ(max) = 165°C, VCC(max) = 24 V, and
ICC(max) = 17 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
Tmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = Tmax ÷ RJA = 15°C ÷ 165 °C/W = 91 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 91 mW ÷ 17 mA = 5 V
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤VCC(est).
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced
RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
(3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 4 mA, and RJA = 140 °C/W, then:
PD = VCC × ICC = 12 V × 4 mA = 48 mW

T = PD × RJA = 48 mW × 140 °C/W = 7°C
TJ = TA + T = 25°C + 7°C = 32°C
A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max),
at a selected RJA and TA.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Device Qualification Program
Contact Allegro for information.
EMC (Electromagnetic Compatibility) Requirements
Contact your local representative for EMC results.
Test Name
Reference Specification
ESD – Human Body Model
AEC-Q100-002
ESD – Machine Model
AEC-Q100-003
Conducted Transients
ISO 7637-2
Direct RF Injection
ISO 11452-7
Bulk Current Injection
ISO 11452-4
TEM Cell
ISO 11452-3
Pin-out Drawings
Package LH, 3-pin SOT
Package UA, 3-pin SIP
3
NC
1. VCC
2. No connection
3. GND
1
2
1. VCC
2. GND
3. GND
1
2
3
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Package LH, 3-Pin; (SOT-23W)
+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
+0.10
0.05 –0.05
0.95 BSC
0.40 ±0.10
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
NNT
1
C
Standard Branding Reference View
N = Last two digits of device part number
T = Temperature code
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
A1145 and
A1146
Package UA, 3-Pin SIP
+0.08
4.09 –0.05
45°
B
C
E
2.04
1.52 ±0.05
1.44 E
Mold Ejector
Pin Indent
+0.08
3.02 –0.05
E
Branded
Face
45°
1
2.16
MAX
D Standard Branding Reference View
= Supplier emblem
N = Last two digits of device part number
T = Temperature code
0.79 REF
A
0.51
REF
NNT
1
2
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
Copyright ©2004-2010, 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
12
Similar pages