DESCRIPTION
The A1244 is a two-wire Hall-effect latch. The devices are
produced on the Allegro
™
advanced BiCMOS wafer fabrication
process, which implements a high-frequency, 4-phase, chopper
stabilization technique. This technique achieves magnetic
stability over the full operating temperature range, and eliminates
offsets inherent in devices with a single Hall element that are
exposed to harsh application environments.
Two-wire latches are particularly advantageous in cost-sensitive
applications because they require one less wire for operation
versus the more traditional open-collector output switches.
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.
The Hall-effect latch will be in the high output current state
in the presence of a magnetic south polarity field of sufficient
magnitude and will remain in this state until a sufficient north
polarity field is present.
The device is offered in two package styles. The LH is a
SOT-23W style, miniature low-profile package for surface-
mount applications. The UA is a 3-pin ultra-mini single inline
package (SIP) for through-hole mounting. Both packages are
lead (Pb) free, with 100% matte-tin leadframe plating.
A1244-DS, Rev. 6
MCO-0000179
FEATURES AND BENEFITS
▪AEC-Q100automotivequalified
▪High-speed,4-phasechopperstabilization
▫Lowswitchpointdriftthroughouttemperaturerange
▫Lowsensitivitytothermalandmechanicalstresses
▪On-chipprotection
▫Supplytransientprotection
▫Reverse-batteryprotection
▪On-boardvoltageregulator
▫3to24Voperation
▪Solid-statereliability
▪RobustEMCandESDperformance
▪Industry-leadingISO7637-2performancethroughuseof
proprietary,40Vclampingstructures
Chopper-Stabilized, Two-Wire Hall-Effect Latch
Functional Block Diagram
A1244
Amp
Regula
To all subcircuits
tor
Schmitt
Trigger
Polarity
Low-Pass
Filter
GND
VCC
GND
UA package only
0.01 µF
V+
Clock/Logic
Dynamic Offset
Cancellation
Sample and Hold
Not to scale
PACKAGES:
Approximate footprint
3-pin SOT23-W
2 mm × 3 mm × 1 mm
(suffix LH)
3-pin ultra-mini SIP
1.5 mm × 4 mm × 3 mm
(suffix UA)
July 21, 2022
Chopper-Stabilized, Two-Wire Hall-Effect Latch
A1244
2
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
NC
1
2
3
1
3
2
ABSOLUTE MAXIMUM RATINGS
Characteristic Symbol Notes Rating Unit
Forward Supply Voltage
[2]
V
CC
28 V
Reverse Supply Voltage V
RCC
–18 V
Magnetic Flux Density B Unlimited G
Operating Ambient Temperature T
A
Range L –40 to 150 °C
Maximum Junction Temperature T
J
(max) 165 °C
Storage Temperature T
stg
–65 to 170 °C
[2]
This rating does not apply to extremely short voltage transients such as Load Dump and/or ESD. Those events have individual
ratings, specific to the respective transient voltage event.
SELECTION GUIDE
Part Number Packing
[1]
Package
Operating Ambient
Temperature, T
A
(°C)
Supply Current
at I
CC(L)
(mA)
A1244LLHLT-I1-T 7-in. reel, 3000 pieces/reel 3-pin SOT23W surface mount –40 to 150 5 to 6.9
A1244LLHLX-I1-T 13-in. reel, 10000 pieces/reel 3-pin SOT23W surface mount –40 to 150 5 to 6.9
A1244LLHLT-I2-T 7-in. reel, 3000 pieces/reel 3-pin SOT23W surface mount –40 to 150 2 to 5
A1244LLHLX-I2-T 13-in. reel, 10000 pieces/reel 3-pin SOT23W surface mount –40 to 150 2 to 5
A1244LUA-I1-T Bulk, 500 pieces/bag 3-pin SIP through hole –40 to 150 5 to 6.9
A1244LUA-I2-T Bulk, 500 pieces/bag 3-pin SIP through hole –40 to 150 2 to 5
[1]
Contact Allegro
™
for additional packing options.
Pinout Diagrams
LH Package
3-pin SOT23W
UA Package
3-pin SIP
Terminal List Table
Name
Number
Function
LH UA
VCC 1 1 Connects power supply to chip
NC 2 – No connection
GND 3 2, 3 Ground
Chopper-Stabilized, Two-Wire Hall-Effect Latch
A1244
3
Allegro MicroSystems
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
ELECTRICAL CHARACTERISTICS: Valid at T
A
= –40°C to 150°C, T
J
< T
J
(max), C
BYP
= 0.01 µF, through operating supply
voltage range, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Supply Voltage
[1][2]
V
CC
Operating, T
J
≤ 165°C 3.0 – 24 V
Supply Current
I
CC(L)
-I1 B < B
RP
5 – 6.9 mA
-I2 B < B
RP
2 – 5 mA
I
CC(H)
B > B
OP
12 – 17 mA
Supply Zener Clamp Voltage V
Z(sup)
I
CC(L)
(max) + 3 mA, T
A
= 25°C 28 – – V
Supply Zener Clamp Current I
Z(sup)
V
Z(sup)
= 28 V – –
I
CC(L)
(max)
+ 3 mA
mA
Reverse Supply Current I
RCC
V
RCC
= –18 V – – –1.6 mA
Output Slew Rate
[3]
di/dt
No bypass capacitor, capacitance of probe
C
S
= 20 pF
– 90 – mA /µs
Chopping Frequency f
c
– 700 – kHz
Power-Up Time
[2][4][5]
t
on
– – 25 µs
Power-Up State
[4][6][7]
POS t
on
< t
on
(max) , V
CC
slew rate > 25 mV / µs – I
CC(H)
– –
[1]
V
CC
represents the generated voltage between the VCC pin and the GND pin.
[2]
The V
CC
slew rate must exceed 600 mV/ms from 0 to 3 V. A slower slew rate through this range can affect device performance.
[3]
Measured without bypass capacitor between VCC and GND. Use of a bypass capacitor results in slower current change.
[4]
Power-Up Time is measured without and with bypass capacitor of 0.01 µF, B < B
RP
– 10 G. Adding a larger bypass capacitor would cause longer
Power-Up Time.
[5]
Guaranteed by characterization and design.
[6]
Power-Up State as defined is true only with a V
CC
slew rate of 25 mV / µs or greater.
[7]
For t > t
on
and B
RP
< B < B
OP
, Power-Up State is not defined.
MAGNETIC CHARACTERISTICS
[8]
: Valid at T
A
= –40°C to 150°C, T
J
< T
J
(max), unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
[9]
Magnetic Operating Point B
OP
5 – 80 G
Magnetic Release Point B
RP
–80 – –5 G
Hysteresis B
HYS
B
OP
– B
RP
40 – 110 G
[8]
Relative values 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).
[9]
1 G (gauss) = 0.1 mT (millitesla).
