ALLEGRO A1148EUATI

A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
The A1147 and A1148 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.
Package LH, 3-pin SOT
≈1:1
Package UA, 3-pin SIP
≈1:1
Commonly found in a number of automotive applications, these switches are
utilized to sense seat track position, seat belt buckle presence, hood/trunk latching, and shift selector position. Two-wire unipolar switches, such as the A1147
and A1148, 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 feature on-chip transient protection and a Zener clamp
to protect against overvoltage conditions on the supply line.
The output currents of the A1148 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 A1147 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 SOT-23W, 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: A1180 and A1181.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .......................................... 28 V
Reverse-Supply Voltage, VRCC ........................ –18 V
Magnetic Flux Density, B .........................Unlimited
Power Dissipation, PD ............................ Graph, p. 5
Operating Temperature
Ambient, TA, Range E.................. –40ºC to 85ºC
Ambient, TA, Range L................ –40ºC to 150ºC
Maximum Junction, TJ(max)........................165ºC
Storage Temperature, TS .................. –65ºC to 170ºC
A1147-DS, Rev. 6
Features and Benefits
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
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Functional Block Diagram
V+
VCC
Regulator
To All Subcircuits
Clock/Logic
Amp
Sample and Hold
Dynamic Offset
Cancellation
0.01 uF
Low-Pass
Filter
GND
GND
Package UA Only
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
2
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
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 A1147; B < BRP for A1148
2
–
5
mA
ICCH
B > BOP for A1148; B < BRP for A1147
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
–
–
8
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
A1147
ICC = ICCL
A1148
ICC = ICCH
A1147
ICC = ICCH
A1148
ICC = ICCL
BHYS = BOP – BRP
Min.
Typ.*
Max.
Units
20
37
80
G
10
22
60
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.
3
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Characteristic Data
Supply Current (Low) versus Ambient Temperature
at Various Levels of VCC
(A1147 and A1148)
Supply Current (High) versus Ambient Temperature
at Various Levels of VCC
(A1147 and A1148)
20
10
18
8
6
3.5 V
12.0 V
24.0 V
4
VCC
ICCH (mA)
ICCL (mA)
VCC
16
3.5 V
12.0 V
24.0 V
14
12
2
0
–50
0
50
100
150
10
–50
200
0
Ambient Temperature, TA (°C)
Operate Point versus Ambient Temperature
at Various Levels of VCC
(A1147 and A1148)
40
60
35
150
200
30
50
VCC
40
3.5 V
12.0 V
24.0 V
30
15
10
10
5
50
100
Ambient Temperature, TA (°C)
150
200
3.5 V
12.0 V
24.0 V
20
20
0
VCC
25
BHYS (G)
BOP (G)
100
Switchpoint Hysteresis versus Ambient Temperature
at Various Levels of VCC
(A1147 and A1148)
70
0
–50
50
Ambient Temperature, TA (°C)
0
–50
0
50
100
150
200
Ambient Temperature, TA (°C)
4
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
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
5
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Functional Description
Operation
The output, ICC, of the A1147 device switches low after the magnetic field at the Hall sensor 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 allows
I+
clean switching of the output even in the presence of external
mechanical vibration and electrical noise. The A1148 device
switches with opposite polarity for similar BOP and BRP values,
in comparison to the A1147 (see figure 1).
I+
Switch to High
ICC
ICC
ICC(H)
Switch to Low
Switch to Low
Switch to High
ICC(H)
ICC(L)
BRP
BHYS
(A) A1147
B+
B–
BRP
BOP
B–
ICC(L)
0
BOP
0
B+
BHYS
(B) A1148
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).
6
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
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 sensor. 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 sensor 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)
7
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current 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.
8
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current 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, RθJA, 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, RθJC, is
relatively small component of RθJA. 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)
ΔT = PD × RθJA
(2)
TJ = TA + ΔT
(3)
Example: Reliability for VCC at TA = 150°C, package UA, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
RθJA = 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:
ΔTmax = 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) = ΔTmax ÷ RθJA = 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
RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 4 mA, and RθJA = 140 °C/W, then:
PD = VCC × ICC = 12 V × 4 mA = 48 mW
ΔT = PD × RθJA = 48 mW × 140 °C/W = 7°C
TJ = TA + ΔT = 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 RθJA and TA.
9
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
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 7637-1
Direct RF Injection
ISO 11452-7
Bulk Current Injection
ISO 11452-4
TEM Cell
ISO 11452-3
10
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Product Selection Guide
Use the complete part numbers when ordering
Part Number
A1147ELHLT
–
A1147ELHLT-T
Yes
A1147EUA
–
A1147EUA-T
Yes
A1147EUATI
–
A1147EUATI-T
Yes
A1147LLHLT
–
A1147LLHLT-T
Yes
A1147LUA
–
A1147LUA-T
Yes
A1147LUATI
–
A1147LUATI-T
Yes
A1148ELHLT
–
A1148ELHLT-T
Yes
A1148EUA
–
A1148EUA-T
Yes
A1148EUATI
–
A1148EUATI-T
Yes
A1148LLHLT
–
A1148LLHLT-T
Yes
A1148LUA
–
A1148LUA-T
Yes
A1148LUATI
–
A1148LUATI-T
aContact Allegro
bSouth
Packinga
Pb-Free
Yes
Tape and Reel, 3000 pieces/reel
Package
Operating Ambient
Temperature, TA
(°C)
Output Level in
South (+) Fieldb
Surface Mount
Bulk Bag, 500 pieces/bag
–40 to 85
Through Hole
Tape and Reel, 2000 pieces/reel
Low
Tape and Reel, 3000 pieces/reel
Surface Mount
Bulk Bag, 500 pieces/bag
–40 to 150
Through Hole
Tape and Reel, 2000 pieces/reel
Tape and Reel, 3000 pieces/reel
Surface Mount
Bulk Bag, 500 pieces/bag
–40 to 85
Through Hole
Tape and Reel, 2000 pieces/reel
High
Tape and Reel, 3000 pieces/reel
Surface Mount
Bulk Bag, 500 pieces/bag
–40 to 150
Through Hole
Tape and Reel, 2000 pieces/reel
for additional packing options.
(+) magnetic fields must be of sufficient strength.
11
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Package LH, 3-Pin; (SOT-23W)
3.10 .122
2.90 .114
1.49 .059
NOM
3
8º
0º
0.28 .011
NOM
0.70 .028
BSC
0.20 .008
0.13 .005
C
0.96 .038
NOM
2.10 .083
1.85 .073
2.40 .094
BSC
A
0.25 .010
MIN
3.00 .118
2.70 .106
1.00 .039
BSC
1
2
0.95 .037
BSC
0.25 .010
BSC
Seating Plane
Gauge Plane
0.50 .020
0.30 .012
1.13 .045
0.87 .034
0.55 .022
REF
A
Dimensions in millimeters
U.S. Customary dimensions (in.) in brackets, for reference only
Hall element
B
Active Area Depth 0.28 [.011]
C
Fits SC–59A Solder Pad Layout
0.15 .006
0.00 .000
0.95 .037
BSC
Package UA, 3-Pin SIP
.164 4.17
.159 4.04
45°
BSC
.0195 0.50
NOM
.0805 2.04
NOM
.122 3.10
.117 2.97
.062 1.57
.058 1.47
.0565 1.44
NOM
45°
BSC
B
.085 2.16
MAX
.640 16.26
.600 15.24
.031 0.79
REF
A
1
2
3
.017 0.44
.014 0.35
.019 0.48
.014 0.36
.050 1.27
BSC
Dimensions in inches
Metric dimensions (mm) in brackets, for reference only
A Dambar removal protrusion
B Hall element
12
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
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 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 infringement of patents or other rights of third
parties which may result from its use.
Copyright © 2004, 2005 Allegro MicroSystems, Inc.
13
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com