3195
PROTECTED, HIGH-TEMPERATURE,
HALL-EFFECT LATCH WITH ACTIVE PULL-DOWN
These Hall-effect latches are capable of sensing magnetic fields
while using an unprotected power supply. The A3195– can provide
position and speed information by providing a digital output for mag-
netic fields that exceed their predefined switch points. These devices
operate down to zero speed and have switch points that are designed
to be extremely stable over a wide operating temperature and voltage
range. The latching characteristics make them ideal for use in pulse
counting applications when used with a multi-pole ring magnet.
A 25 mA high-side driver combined with an active pull-down is espe-
cially useful for driving capacitive loads. Output short-circuit protection
allows for an increased wiring harness fault tolerance. The tempera-
ture compensated switch points, the wide operating voltage range, and
the integrated protection make these devices ideal for use in automo-
tive applications such as transmission speed sensors and integrated
wheel bearing speed sensors.
Each monolithic device contains an integrated Hall-effect trans-
ducer, a temperature-compensated comparator, a voltage regulator,
and a buffered high-side driver with an active pull-down. Supply
protection is made possible by the integration of overvoltage shutdown
circuitry that monitors supply fault conditions. Output protection
circuitry includes source and sink current current limiting for short
circuits to supply or ground.
The A3195E– is rated for operation over a temperature range of
-40°C to +85°C; the A3195L– is rated for operation over an extended
temperature range of -40°C to +150°C. They are supplied in a three-
lead SIP (suffix –U) or a surface-mount SOT89 (suffix –LT).
Data Sheet
27609.15‡
X
LATCH
V
CC
1
2
3
GROUND
Dwg. PH-013
Pinning is shown viewed from branded side.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
(100 ms) ..........
115 V*
(continuous) ...................................
26 V
Reverse Battery Voltage,
V
RCC
(100 ms) ............................
-100 V
(continuous) .................................
-30 V
Magnetic Flux Density, B ...........
Unlimited
Reverse Output Voltage, V
OUT
.........
-0.5 V
Continuous Output Current,
I
OUT
...........................................
-25 mA†
Package Power Dissipation,
P
D
........................................
See Graph
Junction Temperature, T
J
.................
170
°
C
Operating Temperature Range, T
A
Suffix “E–” ....................
-40
°
C to +85
°
C
Suffix “L–” ..................
-40
°
C to +150
°
C
Storage Temperature, T
S
.................
170
°
C
*Fault condition, internal overvoltage shutdown
above 28 V.
†Internal current limiting is intended to protect the
device from output short circuits.
OUTPUT
SUPPLY
FEATURES
s
s
s
s
s
s
s
s
s
s
Internal Protection For Automotive (ISO/DIN) Transients
Operation From Unregulated Supply
Reverse Battery Protection
Undervoltage Lockout
Supply Noise-Suppression Circuitry
Output Short-Circuit Protection
Output Zener Clamp
Thermal Protection
Symmetrical Latching Switch Points
Operable with Multipole Ring Magnets
Always order by complete part number, e.g.,
A3195LU .
3195
PROTECTED, HIGH-TEMP.,
ACTIVE PULL-DOWN
HALL-EFFECT LATCH
3.8 V TO 26 V
WITH TRANSIENTS
V
CC
1
C
BYPASS
X
3
TO
µP
C
L
R
L
2
Dwg. EH-007
OPERATION
In operation, the output transistor is OFF
until the strength of the magnetic field
perpendicular to the surface of the chip
exceeds the threshold or operate point (B
OP
).
When the field strength exceeds B
OP
, the
output transistor switches ON (a logic low)
and is capable of sinking 35 mA of current.
The output transistor switches OFF (a
logic high) when magnetic field reversal
results in a magnetic flux density below the
OFF threshold (B
RP
). This is illustrated in the
transfer characteristics graph (page 2). Note
that the device latches; that is, a south pole
of sufficient strength will turn the device ON.
Removal of the south pole will leave the
device ON. The presence of a north pole of
sufficient strength is required to turn the
device OFF.
The switch points increase in sensitivity
with increasing temperature to compensate
for the typical ferrite magnet temperature
characteristic. The simplest form of magnet
that will operate these devices is a ring
magnet. Other methods of operation are
possible.
TEST CIRCUIT AND
TYPICAL APPLICATION
An external 0.1
µF
to 0.47
µF
capacitor, with good high-frequency
characteristics, should be connected between terminals 1 and 2 to
bypass high-voltage noise and reduce EMI susceptibility.
Internal Pull-Down Resistor.
An internal pull-down resistor
(nominal 15 kΩ) is provided to allow testing of the device without the
need for an external load.
20
18
Ω
PULL-DOWN RESISTANCE IN kΩ
16
14
12
10
-50
-25
0
25
50
75
100
125
150
AMBIENT TEMPERATURE IN
°
C
Dwg. GH-060
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