A3250 and A3251
Field-Programmable, Chopper-Stabilized
Unipolar Hall-Effect Switches
The A3250 and A3251 are field-programmable, chopper-stabilized, unipolar Hall-
effect switches designed for use in high-temperature applications. These devices
use a chopper-stabilization technique to eliminate offset inherent in single-element
devices.
Package UA, 3-pin SIP
The A3250 and A3251 are externally programmable devices. The devices have a
wide range of programmability of the magnetic operate point (B
OP
) while the hys-
teresis remains fixed. This advanced feature allows for optimization of the sensor
switchpoint and can drastically reduce the effects of variations found in a produc-
tion environment, such as magnet and device placement tolerances.
These devices provide on-chip transient protection. A Zener clamp on the power
supply protects against overvoltage conditions on the supply line. These devices
also include short-circuit protection on the output.
The output of the A3250 switches LOW when subjected to a south-polarity mag-
netic field with a flux density that exceeds the threshold for B
OP
, and switches
HIGH when the field drops below the magnetic release point, B
RP
. The output of
the A3251 has the opposite polarity, switching HIGH in a south-polarity magnetic
field that B
OP
, and switching LOW when the field drops below B
RP
.
The other differences in the devices are the power-on state. The A3250 powers-on
in the HIGH state, while the A3251 powers-on in the LOW state.
These devices are available in a TO-92 three-lead ultra-mini SIP (Single In-line
Package), with either straight or formed and trimmed lead configuration.
TL Option
1
2
3
1. VCC
2. GND
3. VOUT
Features and Benefits
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
......................................
26.5 V
Reverse-Supply Voltage, V
RCC
........................
–18 V
Zener Overvoltage, V
Z
.......................................
30 V
Output Current, I
OUT
.........................................20
mA
Magnetic Flux Density, B .........................Unlimited
Operating Temperature
Ambient, T
A
, Range J.................
–40ºC to 115ºC
Ambient, T
A
, Range L................
–40ºC to 150ºC
Maximum Junction, T
J(max)
........................165ºC
Storage Temperature, T
S
..................
–65ºC to 170ºC
Chopper stabilization for stable switchpoints
throughout operating temperature range
Externally programmable operate point
(through VCC pin)
On-board voltage regulator for 4.2 V to 24 V
operation
On-chip protection against:
Supply transients
Output short-circuits
Reverse-battery condition
Use the following complete part numbers when ordering:
Part Number
A3250JUA
A3250JUATL
A3250LUA
A3250LUATL
A3251JUA
A3251JUATL
A3251LUA
A3251LUATL
Package
Straight lead
Formed lead
Straight lead
Formed lead
Straight lead
Formed lead
Straight lead
Formed lead
T
A
(ºC)
–40 to 115
–40 to 150
–40 to 115
–40 to 150
V
OUT
B
hys(typ)
(G)
Power-On Running*
18
High
13
18
Low
13
High
Low
*In south polarity magnetic field of sufficient strength.
A3250-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3250 and A3251
Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches
Functional Block Diagram
VCC
Program/Lock
Programming
Logic
Regulator
Offset Adjust
Sample and Hold
Dynamic Offset
Cancellation
VOUT
Amp
Current Limit
Low-Pass
Filter
GND
Hysteresis Curves
A3250
Hysteresis of
∆V
OUT
Switching Due to
∆B
V
OUT(off)
A3251
Hysteresis of
∆V
OUT
Switching Due to
∆B
V
OUT(off)
V+
V+
Switch to High
Switch to High
Switch to Low
Switch to Low
V
OUT
V
OUT
V
OUT(on)(sat)
V
OUT(on)(sat)
B
RP
B
HYS
B
HYS
Output voltage in relation to sensed magnetic flux density in a
south polarity magnetic field of sufficient strength. Transition
through B
OP
must precede transition through B
RP
.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
B
OP
B+
B+
B
RP
B
OP
2
A3250-DS
A3250 and A3251
Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches
OPERATING CHARACTERISTICS
valid over operating T
A
and V
CC
, unless otherwise specified
Characteristic
ELECTRICAL CHARACTERISTICS
Supply Voltage
1
Output Saturation Voltage
Output Leakage Current
V
CC
V
OUT(sat)
I
OFF
I
CC(off)
Supply Current
I
CC(on)
Output Rise Time
Output Fall Time
Chopping Frequency
Power-Up Time
Output Current Limit
1,2
Power-On State
MAGNETIC CHARACTERISTICS
Initial Operate Point
Temperature Drift of B
OP
Hysteresis (B
OP
– B
RP
)
B
OP
∆B
OP
B
hys
B
OP
≤
500 gauss
Package T
A
range = J
Package T
A
range = L
–20
–35
5.0
5.0
13
–
18
13
50
35
35
35
G
G
G
G
t
r
t
f
f
C
t
on
I
OUT(lim)
POS
V
OUT
= HIGH
Short-circuit protection
A3250; B < B
RP
, t > t
on
A3251; B < B
RP
, t > t
on
Running mode
I
OUT
= 20 mA; Switch state = ON
V
OUT
= 24 V; Switch state = OFF
A3250; B < B
RP
; V
OUT
= HIGH
A3251; B > B
OP
; V
OUT
= HIGH
A3250; B > B
OP
; V
OUT
= LOW
A3251; B < B
RP
; V
OUT
= LOW
R
LOAD
= 820
Ω,
C
LOAD
= 10 pF
R
LOAD
= 820
Ω,
C
LOAD
= 10 pF
4.2
–
–
–
–
–
–
–
–
–
–
60
–
–
–
175
–
4.0
4.0
6.0
6.0
–
–
340
20
90
HIGH
LOW
24
400
10
7.0
7.0
10.0
10.0
5.0
5.0
–
50
120
–
–
V
mV
µA
mA
mA
mA
mA
µs
µs
kHz
µs
mA
mV
mV
Symbol
Test Conditions
Min.
Typ.
Max.
Units
PROGRAMMING CHARACTERISTICS
Programmable B
OP
Values
3
Number of Programming Bits
Resolution
B
OP(prog)
–
B
RES
Switchpoint set
Programming lock
50
–
–
–
–
6
1
7.0
≥350
–
–
–
G
Bit
Bit
G
TRANSIENT PROTECTION CHARACTERISTICS
Supply Zener Voltage
Supply Zener Current
Reverse Battery Current
1
2
3
V
Z
I
Z
I
RCC
V
CC
= 28 V
V
RCC
= –18 V, T
J
< T
J(max)
28
–
–
–
–
–
–
13
–5.0
V
mA
mA
Do not exceed TJ(max): Additional information on power derating is provided in the applications section.
Short-circuit protection is not intended for continuous operation; permanent damage may result.
Device can be used below 50 G but is not guaranteed to be a unipolar switch. It is the responsibility of the programmer to verify that the desired
switchpoint has been achieved.
A3250-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
A3250 and A3251
Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches
Typical Characterization Data
All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot
Average B
OP
vs. T
A
Program Code: 1, V
CC
= 12 V
30
Average B
RP
vs. T
A
Program Code: 1, V
CC
= 12 V
10
Average B
RP
(G)
-20
10
40
70
T
A
(°C)
100
130
160
Average B
OP
(G)
25
20
15
10
5
0
-5
-50
5
0
-5
-10
-15
-20
-50
-20
10
40
70
T
A
(°C)
100
130
160
Average B
OP
vs. T
A
Program Code: 8, V
CC
= 12 V
75
Average B
RP
vs. T
A
Program Code: 8, V
CC
= 12 V
60
Average B
OP
(G)
Average B
RP
(G)
70
65
60
55
50
45
40
-50
-20
10
40
70
T
A
(°C)
100
130
160
50
40
30
20
-50
-20
10
40
70
T
A
(°C)
100
130
160
Average B
OP
vs. T
A
Program Code: 16, V
CC
= 12 V
130
Average B
RP
vs. T
A
Program Code: 16, V
CC
= 12 V
110
Average B
OP
(G)
125
120
115
110
105
100
-50
-20
10
40
70
T
A
(°C)
100
130
160
Average B
RP
(G)
105
100
95
90
85
80
-50
-20
10
40
70
T
A
(°C)
100
130
160
A3250-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
A3250 and A3251
Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches
Typical Characterization Data
All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot
Average B
hys
vs. Temperature
Program Code: 1, V
CC
= 12 V
35
Average B
HYS
(G)
Average B
hys
vs. Temperature
Program Code: 16, V
CC
= 12 V
35
Average B
HYS
(G)
30
25
20
15
10
5
0
-50
-20
10
40
T
A
(°C)
30
25
20
15
10
5
0
-50
-20
10
40
70
T
A
(°C)
100
130
160
70
100
130
160
Average B
hys
vs. Temperature
Program Code: 8, V
CC
= 12 V
30
Average B
OP
vs. Temperature
-40°C to 25°C and 150°C to 25°C
20
10
0
Code 1
Code 8
Code 16
35
Average B
HYS
(G)
30
25
20
15
10
5
0
-50
-20
10
40
T
A
(°C)
70
100
130
160
Average B
OP
(G)
-10
-20
-30
-40°C to 25°C
150°C to 25°C
T
A
(°C)
A3250-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
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