Allegro A1242EUA-I2-T Two-wire chopper-stabilized hall effect latch Datasheet

A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
The A1242 Hall effect latch is a two-wire latch especially suited for operation
over extended temperature ranges, from –40 to +150°C. Superior high-temperature performance is made possible through the Allegro® patented dynamic offset
cancellation technique, which reduces the residual offset voltage normally caused
by device overmolding, temperature dependencies, and thermal stress.
Package LH, 3-pin Surface Mount
3
1
3
2
The Hall effect latch will be in the high output current state in the presence of a
magnetic South Pole field of sufficient magnitude and will remain in this state
until a sufficient North Pole field is present.
NC
1
The current-switching output technique allows for the reduction in cost in the
wiring harness because only two connections to the sensor are required. The current-switching output structure also inherently provides more immunity against
EMC/ESD transients. These sensors have low magnetic thresholds, thereby
enabling more flexibility in the magnetic circuit design.
2
The A1242 includes the following on a single silicon chip: a voltage regulator,
Hall-voltage generator, small-signal amplifier, chopper stabilization, Schmitt trigger, and a current source output. Advanced BiCMOS wafer fabrication processing takes advantage of low-voltage requirements, component matching, very low
input-offset errors and small component geometries.
Package UA, 3-pin SIP
Suffix ‘L-’ devices are rated for operation over a temperature range of –40°C
to +150°C; suffix ‘E-’ devices are rated for operation over a temperature range
of –40°C to +85°C. Two A1242 package styles provide magnetically optimized
solutions for most applications. Package LH is a SOT23W, a miniature low-profile surface-mount package, while package UA is a three-lead ultra-mini SIP for
through-hole mounting. Each package is available lead (Pb) free, with 100% matte
tin plated leadframes.
1
2
3
Features and Benefits
1 2
3
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .......................................... 28 V
Reverse-Supply Voltage, VRCC ........................ –18 V
Magnetic Flux Density, B .........................Unlimited
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
A1242-DS
Chopper stabilization
– Superior temperature stability
– Extremely low switchpoint drift
– Insensitive to physical stress
Reverse battery protection
Solid-state reliability
Small size
Robust EMC capability
High ESD ratings (HBM)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
Product Selection Guide
Part Number
Packaging*
Mounting
A1242ELHLT-I1-T
7-in. reel, 3000 pieces/reel
A1242ELHLT-I2-T
A1242EUA-I1-T
Bulk, 500 pieces/bag
A1242EUA-I2-T
A1242LLHLT-I1-T
7-in. reel, 3000 pieces/reel
A1242LLHLT-I2-T
A1242LUA-I1-T
Bulk, 500 pieces/bag
A1242LUA-I2-T
*Contact Allegro for additional packing options.
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SIP through hole
Low Current, ICC(L)
(mA)
5.0 to 6.9
2.0 to 5.0
5.0 to 6.9
2.0 to 5.0
5.0 to 6.9
2.0 to 5.0
5.0 to 6.9
2.0 to 5.0
Ambient, TA
(°C)
BRP(MIN)
(G)
BOP(MAX)
(G)
–80
80
–40 to 85
–40 to 150
Functional Block Diagram
VCC
Regulator
To All Subcircuits
Amp
Sample and Hold
Dynamic Offset
Cancellation
Clock/Logic
Low-Pass
Filter
GND
GND
Package UA Only
Terminal List
Name
VCC
GND
NC
Description
Connects power supply to chip
Ground
No internal connection
Number
Package LH Package UA
1
1
3
2,3
2
–
2
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
ELECTRICAL CHARACTERISTICS over full operating voltage and temperature ranges, unless otherwise specified
Characteristic
Symbol
Test Conditions
Min.
Typ.1
3.5
–
24
V
5
–
6.9
mA
Max.
Units
Electrical Characteristics
Supply Voltage2 3
Supply Current
Output Slew Rate4
Chopping Frequency
Power-On Time
Power-On State5
VCC
ICC(L)
Operating, TJ < 165°C
-I1, B < BRP
-I2, B < BRP
2
–
5
mA
ICC(H)
-I1 and -I2, B > BOP
12
–
17
mA
dI/dt
RS = 100 Ω, CS = 20 pF, no bypass capacitor
–
36
–
mA/μs
–
200
–
kHz
fC
tPO
POS
VCC > VCC(MIN)
–
–
25
μs
tPO < tPO(max), dVCC / dt > 25 mV / μs
–
ICC(H)
–
–
Supply Zener Clamp Voltage
VZ(supply)
ICC = 20 mA; TA = 25°C
28
–
–
V
Supply Zener Current6
IZ(supply)
VS = 28 V
–
–
20
mA
IRCC
VRCC = –18 V
–
–
2.5
mA
Reverse Battery Current
Magnetic Characteristics7
Operate Point
BOP
South pole adjacent to branded face of device
5
32
80
G
Release Point
BRP
North pole adjacent to branded face of device
–80
–32
–5
G
Hysteresis
BHYS
BOP – BRP
40
64
110
G
1
Typical values are at TA = 25°C and VCC = 12 V. Performance may vary for individual units, within the specified maximum and minimum
limits.
2 Maximum voltage must be adjusted for power dissipation and junction temperature; see Power Derating section.
3V
CC represents the generated voltage between the VCC pin and the GND pin.
4 The value of dI is the difference between 90% of I
CC(H) and 10% of ICC(L), and the value of dt is time period between those two points.
The value of dI/dt depends on the value of the bypass capacitor, if one is used, with greater capacitances resulting in lower rates of
change.
5 For t > t
PO(max), and BRP < B < BOP, POS is undefined.
6 Maximum current limit is equal to the maximum I
CCL(max) + 3 mA.
7 Magnetic flux density, B, is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity
magnetic fields. This so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the relative
strength of the field is indicated by the absolute value of B, and the sign indicates the polarity of the field (for example, a –100 G field and
a 100 G field have equivalent strength, but opposite polarity).
DEVICE QUALIFICATION PROGRAM
Contact Allegro for information.
EMC (Electromagnetic Compatibility) PERFORMANCE
Contact Allegro for information.
3
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
RθJA
Package Thermal Resistance
Test Conditions*
Package LH, minimum-K PCB (single layer, single-sided with
copper limited to solder pads)
Package LH, low-K PCB (single layer, double-sided with
0.926 in2 copper area)
Package UA, minimum-K PCB (single layer, single-sided with
copper limited to solder pads)
Value Units
228
ºC/W
110
ºC/W
165
ºC/W
*Additional information available on the Allegro Web site.
Maximum Allowable VCC (V)
Power Derating Curve
TJ(max) = 165°C; ICC = ICC(max)
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)
Low-K PCB, Package LH
(R JA = 110 °C/W)
Minimum-K PCB, Package UA
(R JA = 165 °C/W)
Minimum-K PCB, Package LH
(R JA = 228 °C/W)
20
40
60
80
100
VCC(min)
120
140
160
180
Temperature (°C)
Power Dissipation, P D (mW)
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
Low-K PCB, Package LH
(R JA = 110 °C/W)
Min-K PCB, Package UA
(R JA = 165 °C/W)
Min-K PCB, Package LH
(R JA = 228 °C/W)
20
40
60
80
100
120
140
160
180
Temperature (°C)
4
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
Characteristic Data
Supply Current (Low) versus Ambient Temperature
(1242- I1)
Supply Current (Low) versus Supply Voltage
(A1242-I1)
7.0
7.0
6.8
6.8
6.6
6.6
6.4
Vcc (V)
24
12
3.75
6.2
6.0
5.8
5.6
ICC(L) (mA)
ICC(L) (mA)
6.4
TA (°C)
-40
25
85
150
6.2
6.0
5.8
5.6
5.4
5.4
5.2
5.2
5.0
5.0
-50
0
50
100
0
150
5
10
TA (°C)
5.0
5.0
4.5
4.5
4.0
Vcc (V)
24
12
3.75
3.5
3.0
ICC(L) (mA)
ICC(L) (mA)
20
25
Supply Current (Low) versus Supply Voltage
(A1242-I2)
Supply Current (Low) versus Ambient Temperature
(1242- I2)
4.0
TA (°C)
-40
25
150
3.5
3.0
2.5
2.5
2.0
2.0
-50
0
50
100
0
150
5
10
15
20
25
VCC (V)
T A (°C)
Supply Current (High) versus Ambient Temperature
17
17
16
16
15
Vcc (V)
24
12
3.75
14
ICC(H) (mA)
ICC(H) (mA)
15
VCC (V)
Supply Current (High) versus Supply Voltage
15
TA (°C)
-40
25
85
150
14
13
13
12
12
-50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
5
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
Operate Point versus Supply Voltage
80
65
65
50
Vcc (V)
24
12
3.5
35
BOP (G)
B OP (G)
Operate Point versus Ambient Temperature
80
20
50
TA (°C)
-40
25
150
35
20
5
5
-50
0
50
100
0
150
5
10
TA (°C)
20
25
Release Point versus Supply Voltage
-5
-5
-20
-20
-35
Vcc (V)
24
12
3.5
-50
BRP (G)
B RP (G)
Release Point versus Ambient Temperature
-65
-35
TA (°C)
150
25
-40
-50
-65
-80
-80
-50
0
50
100
150
0
5
10
15
20
25
VCC (V)
TA (°C)
Hysteresis versus Ambient Temperature
Hysteresis versus Supply Voltage
110
110
100
100
90
90
80
Vcc (V)
24
12
3.5
70
60
Bhys (G)
Bhys (G)
15
VCC (V)
80
TA (°C)
-40
25
150
70
60
50
50
40
40
-50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
6
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
Functional Description
• Hall-Effect IC Applications Guide, AN27701,
• Hall-Effect Devices: Gluing, Potting, Encapsulating, Lead Welding
and Lead Forming, AN27703.1
• Soldering Methods for Allegro Products – SMD and Through-Hole,
AN26009
All are provided in Allegro Electronic Data Book, AMS-702
and the Allegro Web site: www.allegromicro.com.
I+
ICC(H)
Switch to Low
.
ICC
TYPICAL APPLICATION CIRCUIT
ICC(L)
0
B–
Installation of CBYP must ensure that the traces that connect it to
the A1242 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 A1242 internal circuitry. As a result, the load
ECU (electronic control unit) must have sufficient protection,
other than CBYP, installed in parallel with the A1242.
A series resistor on the supply side, RS (not shown), in combination with CBYP, creates a filter for EMI pulses.
0
BRP
The A1242 should 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 2, a 0.01 μF capacitor is typical.
Switch to High
The output, ICC, of the A1242 switches to the high current state
when a magnetic field perpendicular to the Hall sensor exceeds
the operate point threshold, BOP. Note that the device latches,
that is, a south pole of sufficient strength towards the branded
surface of the device switches the device output to ICC(H). The
device retains its output state if the south pole is removed. When
the magnetic field is reduced to below the release point threshold, BRP, the device output goes to the low current state. The difference between the magnetic operate and release points is called
the hysteresis of the device, BHYS. This built-in hysteresis allows
clean switching of the output even in the presence of external
mechanical vibration and electrical noise.
Extensive applications information on magnets and Hall-effect
sensors is available in:
B+
BOP
OPERATION
BHYS
Figure 1. Switching Behavior of the A1242. 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).
V+
VCC
When determining the minimum VCC requirement of the A1242
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
A1242
GND
CBYP
0.01 uF
GND
B
A
A
Package UA Only
B
Maximum separation 5 mm
RSENSE
ECU
Figure 2. Typical Application Circuit
7
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
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 field
induced signal to recover its original spectrum at baseband,
while the dc offset becomes a high-frequency signal. The
magnetic sourced signal then can pass through a low-pass filter,
while the modulated dc offset is suppressed. This configuration
is illustrated in Figure 3.
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 high
frequency 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 3. Chopper stabilization circuit (dynamic quadrature offset cancellation)
8
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
Power Derating
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 LH, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
RθJA = 228°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 ÷ 228 °C/W = 66 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 66 mW ÷ 17 mA = 3.9 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 = 6 mA, and RθJA = 165 °C/W, then:
PD = VCC × ICC = 12 V × 6 mA = 72 mW
ΔT = PD × RθJA = 72 mW × 165 °C/W = 12°C
TJ = TA + ΔT = 25°C + 12°C = 37°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
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
Package LH, 3-Pin (SOT-23W)
Package UA, 3-Pin
10
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A1242
Two-Wire Chopper-Stabilized Hall Effect Latch
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 © 2005, Allegro MicroSystems, Inc.
11
A1242-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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