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PDF A1126 Data sheet ( Hoja de datos )
| Número de pieza | A1126 | |
| Descripción | Chopper-Stabilized Omnipolar Hall-Effect Switch | |
| Fabricantes | Allegro | |
| Logotipo |  |
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A1126
Chopper-Stabilized Omnipolar Hall-Effect Switch
Features and Benefits
• AEC-Q100 automotive qualified
• Omnipolar operation
• Low switchpoint drift
• Superior temperature stability
• Insensitive to physical stress
• Reverse-battery protection
• Robust EMC capability
• Robust ESD protection
Packages:
3-pin SOT23-W
2 mm × 3 mm × 1 mm
(suffix LH)
3-pin ultramini SIP
1.5 mm × 4 mm × 3 mm
(suffix UA)
Not to scale
Approximate footprint
Description
The A1126 integrated circuit is an omnipolar, ultrasensitive
Hall-effect switch with a digital output. This device has an
integrated regulator permitting operation to 24 V.
This device is especially suited for operation through extended
temperature ranges, up to 150°C. Superior high-temperature
performance is made possible through an Allegro™ patented
dynamic offset cancellation, which reduces the residual offset
voltage normally caused by device overmolding, temperature
excursions, and thermal stress.
The A1126 Hall-effect switch includes the following on a
single silicon chip: voltage regulator, Hall-voltage generator,
small-signal amplifier, chopper stabilization, Schmitt trigger,
and a short-circuit-protected open-drain output. Advanced
BiCMOS wafer fabrication processing is used to take advantage
of low-voltage requirements, component matching, very low
input-offset errors, and small component geometries.
The omnipolar operation of the A1126 allows activation with
either a north or a south polarity field of sufficient strength. In
the absence of a magnetic field, the output is off. This patented
magnetic-polarity-independence feature makes this device
an excellent replacement for reed switches, with improved
ease of manufacturing, because the A1126 does not require
Continued on the next page…
Functional Block Diagram
VCC
Regulator
To all subcircuits
Amplifier
Signal
Recovery
Omnipolar
Switchpoints
Control
Current
Limit
VOUT
GND
A1126-DS, Rev. 2
1 page  
A1126
Chopper-Stabilized Omnipolar Hall-Effect Switch
Average Operate Point (South) versus Temperature
55
50
45
40
35 VCC = 3.0 V
30
VCC = 24 V
25
20
15
-60 -40 -20 0 20 40 60 80 100 120 140 160
Ambient Temperature, TA (°C)
Average Operate Point (South) versus Supply Voltage
55
50
45
40
35
TA = –40°C
TA = 150°C
30
TA = 25°C
25
20
15
0
5 10 15 20
Supply Voltage, VCC (V)
25
Average Release Point (South) versus Temperature
50
45
40
35
30
25
20
15
10
5
-60
VCC = 3.0 V
VCC = 24 V
-40 -20 0 20 40 60 80 100
Ambient Temperature, TA (°C)
120 140 160
Average Release Point (South) versus Supply Voltage
50
45
40
35
30
25 TA = 150°C
TA = –40°C
20
15
10 TA = 25°C
5
0 5 10 15 20 25
Supply Voltage, VCC (V)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
5 Page 
A1126
Chopper-Stabilized Omnipolar Hall-Effect Switch
Power Derating
The device must be operated below the maximum junction
temperature of the device, TJ(max) . Under certain combina-
tions 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 sum-
marizing 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)
For example, given common conditions such as: TA= 25°C,
VIN = 12 V, IIN = 4 mA, and RθJA = 140 °C/W, then:
× PD = VIN IIN = 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 allow-
able power level, without exceeding TJ(max) , at a selected RθJA
and TA.
Example: Reliability for VCC at TA = 150°C, package UA, using a
single-layer 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) = 4 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 ÷ 4 mA = 23 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 condi-
tions.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet A1126.PDF ] | |
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