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A1225, A1227, and A1229
Hall Effect Latch for High Temperature Operation
Features and Benefits
Symmetrical switchpoints
Superior temperature stability
Operation from unregulated supply
Open-drain 25 mA output
Reverse Battery protection
Activate with small, commercially available
permanent magnets
Solid-state reliability
Small size
Resistant to physical stress
Enhanced ESD structures result in 8 kV HBM ESD
performance without external protection components
Internal protection circuits enable 40 V load dump
compliance without external protection components
Packages:
3-pin SIP
(suffix UA)
Not to scale
3-pin SOT89
(suffix LT)
Description
These Hall-effect latches are extremely temperature-stable
and stress resistant sensor ICs especially suited for operation
over extended temperature ranges to 150°C. Superior high-
temperature performance is made possible through a novel
Schmitt trigger circuit that maintains operate and release
point symmetry by compensating for temperature changes
in the Hall element. Additionally, internal compensation
provides magnetic switchpoints that become more sensitive
with temperature, hence offsetting the usual degradation of
the magnetic field with temperature. The symmetry capability
makes these devices ideal for use in pulse-counting applications
where duty cycle is an important parameter. The three basic
devices (A1225, A1227, and A1229) are identical except for
magnetic switchpoints.
Each device includes on a single silicon chip a voltage regulator,
Hall-voltage generator, temperature compensation circuit,
signal amplifier, Schmitt trigger, and a buffered open-drain
output to sink up to 25 mA. The on-board regulator permits
operation with supply voltages of 3.8 to 24 V.
The first character of the part number suffix determines the
device operating temperature range. Suffix L is for –40°C to
150°C. Two package styles provide a magnetically optimized
package for most applications. Suffix LT is a miniature SOT89/
TO-243AAtransistor package for surface-mount applications,
suffix UAis a three-lead ultra-mini-SIP. Both packages are lead
(Pb) free with 100% matte tin leadframe plating.
Functional Block Diagram
VCC
Regulator
Clock / Logic
To All Subcircuits
VOUT
A1225-DS, Rev. 1
AMP
Anti-aliasing
LP-Filter
Tuned Filter
GND

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A1225, A1227
and A1229
Hall Effect Latch for High Temperature Operation
Selection Guide
Part Number
Packing*
Package
A1225LLTTR-T
7-in. reel, 1000 pieces/reel 3-pin SOT89 surface mount
A1225LUA-T
Bulk, 500 pieces/bag
3-pin SIP through hole
A1227LLTTR-T
7-in. reel, 1000 pieces/reel 3-pin SOT89 surface mount
A1227LUA-T
Bulk, 500 pieces/bag
3-pin SIP through hole
A1229LLTTR-T
7-in. reel, 1000 pieces/reel 3-pin SOT89 surface mount
A1229LUA-T
Bulk, 500 pieces/bag
3-pin SIP through hole
*Contact Allegro® for additional packaging options.
Ambient
Temperature, TA
–40°C to 150°C
–40°C to 150°C
–40°C to 150°C
BRP(min)
(G)
–300
BOP(max)
(G)
300
–175
175
–200
200
Absolute Maximum Ratings
Characteristic
Forward Supply Voltage
Reverse Supply Voltage
Output Off Voltage
Reverse Output Voltage
Continuous Output Current
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
VCC
VRCC
VOUT
VROUT
IOUT(SINK)
TA
TJ(max)
Tstg
Range L
Notes
Rating
30
–30
30
–0.5
25
–40 to 150
165
–65 to 170
Unit
V
V
V
V
mA
ºC
ºC
ºC
Pin-out Diagrams
Package LT
Package UA
123
12
3
Terminal List Table
Number
1
Name
VCC
Function
Input power supply
2 GND Ground
3 VOUT Output signal
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2

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A1225, A1227
and A1229
Hall Effect Latch for High Temperature Operation
ELECTRICAL CHARACTERISTICS Valid at TA = –40°C to 150°C, CBYPASS = 0.1 μF, VCC = 12 V; unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.1
Max.
Electrical Characteristics
Supply Voltage
Supply Current
Supply Zener Voltage
Reverse Battery Current
Power-On Time3
Power-On State
Chopping Frequency
Output Stage Characteristics
VCC
ICC
VZ(sup)
IZ(sup)
tPO
POS
fchop
Operating; TJ 165°C
B < BRP (Output off)
B > BOP (Output on)
ICC = 9 mA, TA = 25°C
VRCC = –28 V, TA = 25°C
B < BOP
3.8
––
––
28 –
–5 –
––
– HIGH
– 400
24
6
6
12
Output Saturation Voltage
Output Leakage Current
Output Rise Time3,4
Output Fall Time3,4
Output Zener Voltage
Magnetic Characteristics
VOUT(sat)
IOFF
tr
tf
VZ(out)
IOUT = 20 mA
VOUT = 24 V, B < BRP
RL= 820 Ω, CL= 20 pF
RL= 820 Ω, CL= 20 pF
IOUT = 3 mA, TA = 25°C
– 175 400
– < 1 10
– 200 2000
– 200 2000
30 –
A1225 TA = 25°C
Over operating temperature range
170 –
140 –
270
300
Operate Point
BOP
A1227 TA = 25°C
Over operating temperature range
50 –
50 –
150
175
A1229 TA = 25°C
Over operating temperature range
100 –
80 –
180
200
A1225 TA = 25°C
Over operating temperature range
–270
–300
–170
–140
Release Point
BRP
A1227 TA = 25°C
Over operating temperature range
–150
–175
–50
–50
A1229 TA = 25°C
Over operating temperature range
–180
–200
–100
–80
A1225 TA = 25°C
Over operating temperature range
340 –
280 –
540
600
Hysteresis (BOP – BRP)
BHYS
A1227 TA = 25°C
Over operating temperature range
100
100 –
300
350
A1229 TA = 25°C
Over operating temperature range
200 –
160 –
360
400
1Typical data are at TA = 25°C and VCC = 12 V, and are for design estimations only.
21 G (gauss) = 0.1 mT (millitesla).
3Minimum and maximum specifications verified by bench characterization and not guaranteed by Allegro final test.
4CL = oscilloscope probe capacitance.
Unit2
V
mA
mA
V
mA
μs
kHz
mV
μA
ns
ns
V
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3