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A1221 Schematic ( PDF Datasheet ) - Allegro

Teilenummer A1221
Beschreibung Chopper-Stabilized Precision Hall-Effect Latches
Hersteller Allegro
Logo Allegro Logo 




Gesamt 16 Seiten
A1221 Datasheet, Funktion
A1220, A1221, A1222, and A1223
Chopper-Stabilized Precision Hall-Effect Latches
Features and Benefits
▪ AEC-Q100 automotive qualified
▪ Symmetrical latch switchpoints
▪ Resistant to physical stress
▪ Superior temperature stability
▪ Output short-circuit protection
▪ Operation from unregulated supply down to 3 V
▪ Reverse-battery protection
▪ Solid-state reliability
▪ Small package sizes
Packages:
Not to scale
3-pin SOT23W
(suffix LH)
(A1220
and 1221)
(A1222
and A1223)
3-pin SIP (suffix UA)
Description
The A1220, A1221, A1222, and A1223 Hall-effect sensor ICs
are extremely temperature-stable and stress-resistant devices
especially suited for operation over extended temperature ranges
to 150°C. Superior high-temperature performance is made
possible through dynamic offset cancellation, which reduces the
residual offset voltage normally caused by device overmolding,
temperature dependencies, and thermal stress. Each device
includes on a single silicon chip a voltage regulator, Hall-
voltage generator, small-signal amplifier, chopper stabilization,
Schmitt trigger, and a short-circuit protected open-drain output
to sink up to 25 mA. A south pole of sufficient strength turns
the output on. A north pole of sufficient strength is necessary
to turn the output off.
An onboard regulator permits operation with supply voltages
of 3 to 24 V. The advantage of operating down to 3 V is that
the device can be used in 3 V applications or with additional
external resistance in series with the supply pin for greater
protection against high voltage transient events.
Two package styles provide magnetically optimized packages
for most applications. Package type LH is a modified 3-pin
SOT23W surface-mount package, while UA is a three-pin
ultra-mini SIP for through-hole mounting. Both packages are
lead (Pb) free, with 100% matte-tin-plated leadframes.
Functional Block Diagram
VCC
Amp
Regulator
Low-Pass
Filter
To All Subcircuits
Control
Current Limit
VOUT
A1220-DS, Rev. 16
GND






A1221 Datasheet, Funktion
A1220, A1221,
A1222, and A1223
Chopper-Stabilized Precision Hall-Effect Latches
Characteristic Performance
A1220, A1221, A1222, and A1223 Electrical Characteristics
Average Supply Current (On) versus Temperature
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-60 -40 -20 0 20 40 60 80 100 120 140 160
TA (°C)
3.0V
3.8V
4.2V
12V
24V
Average Supply Current (On) versus Supply Voltage
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
2
6 10 14 18 22 26
VCC (V)
150°C
25°C
-40°C
Average Supply Current (Off) versus Temperature
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-60 -40 -20 0 20 40 60 80 100 120 140 160
TA (°C)
3.0V
3.8V
4.2V
12V
24V
Saturation Voltage versus Temperature
300
250
200 2.6V
3.0V
150
3.8V
4.2V
12V
100 24V
50
0
-60 -40 -20 0 20 40 60 80 100 120 140 160
TA (°C)
Average Supply Current (Off) versus Supply Voltage
6.0
5.5
5.0
4.5
4.0
3.5 150°C
3.0
25°C
-40°C
2.5
2.0
1.5
1.0
0.5
0.0
2
6 10 14 18 22 26
VCC (V)
Saturation Voltage versus Supply Voltage
300
250
200 150°C
25°C
150 -40°C
100
50
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26
VCC (V)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6

6 Page









A1221 pdf, datenblatt
A1220, A1221,
A1222, and A1223
Chopper-Stabilized Precision Hall-Effect Latches
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 appli-
cation. This section presents a procedure for correlating factors
affecting operating TJ. (Thermal data is also available on the
Allegro MicroSystems website.)
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,
VCC = 12 V, ICC = 1.6 mA, and RθJA = 165 °C/W, then:
A worst-case estimate, PD(max), represents the maximum allow-
able power level (VCC(max), ICC(max)), without exceeding TJ(max),
at a selected RθJA and TA.
Example: Reliability for VCC at TA =150°C, package LH, using a
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)= 4 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔTmax = TJ(max) – TA = 165°C150°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 ÷ 4 mA = 16.4 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 reli-
able 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.
 PD = VCC × ICC = 12 V × 1.6 mA = 19 mW
ΔT = PD × RθJA = 19 mW × 165 °C/W = 3°C
 TJ = TA + ΔT = 25°C + 3°C = 28°C
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12

12 Page





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