Output Current, I
Output OFF Voltage, V
Reverse Output Current, I
Package Power Dissipation,
PD.......................................... See Graph
Operating Temperature Range, T
ATS535JSB................ -40°C to +115°C
ATS535SSB ................. -20°C to +85°C
Storage Temperature, TS................... +170°C
* Operation at increased supply voltages with
external circuitry is described in Applications
Information.
OUT
RCC
..... Internally Limited
................. 26.5 V
OUT
ROUT
Dwg. AH-006-4
............ -30 V
......... -50 mA
A
ATS535JSB
AND
ATS535SSB
The ATS535JSB and ATS535SSB programmable, true power-on
(TPOS), proximity sensors are optimized Hall-effect IC/magnet combinations that provide power-on tooth/valley recognition in large geartooth sensing applications and proximity detection in other applications.
Each sensor subassembly consists of a high-temperature plastic shell
that holds together a samarium-cobalt magnet, a pole piece, and a single
element, chopper-stabilized Hall-effect IC that can be programmed to
match the magnetic circuit, optimizing sensor airgap and timing accuracy performance after final packaging. The small package can be
easily assembled and used in conjunction with a wide variety of gear/
target shapes and sizes. The two devices differ only in operating
temperature range.
The sensing technology used for this sensor subassembly is Halleffect based. The sensor incorporates a single-element Hall IC that
switches in response to magnetic signals created by a ferrous target.
The circuit eliminates magnet and system offsets such as those caused
by tilt yet provides zero-speed detection capabilities without the associated running jitter inherent in classical digital solutions.
A proprietary dynamic offset cancelation technique, with an
internal high-frequency clock, reduces the residual offset voltage,
which is normally caused by device overmolding, temperature
dependancies, and thermal stress. This technique produces devices that
have an extremely stable quiescent output voltage, are immune to
mechanical stress, and have precise recoverability after temperature
cycling. Many problems normally associated with low-level analog
signals are minimized by having the Hall element and amplifier in a
single chip. Output precision is obtained by internal gain adjustments
during the manufacturing process and operate-point programming in the
user’s application.
This sensor system is ideal for use in gathering speed, position, and
timing information using gear-tooth-based configurations. The
ATS535JSB/SSB are particularly suited to those applications that
require accurate duty cycle control or accurate edge detection. The
lower vibration sensitivity also makes these devices extremely useful
for transmission speed sensing.
Continued next page
Always order by complete part number, e.g., ATS535JSB .
proprietary dynamic offset cancellation technique, with an
internal high-frequency clock to reduce the residual offset
voltage of the Hall element that is normally caused by
device overmolding, temperature dependencies, and
thermal stress. This technique produces devices that have
an extremely stable quiescent Hall output voltage, are
immune to thermal stress, and have precise recoverability
after temperature cycling. This technique will also slightly
degrade the device output repeatability.
The Hall element can be considered as a resistor array
similar to a Wheatstone bridge. A large portion of the
offset is a result of the mismatching of these resistors. The
chopper-stabilizing technique cancels the mismatching of
the resistors by changing the direction of the current
flowing through the Hall plate and Hall voltage measurement taps, while maintaining the Hall-voltage signal that is
induced by the external magnetic flux. The signal is, then,
captured by a sample-and-hold circuit.
Operation. The output of these devices switches low
(turns ON) when a magnetic field (south pole) perpendicular to the Hall sensor exceeds the operate point threshold
(BOP). After turn-ON, the output is capable of sinking 25
mA and the output voltage is V
OUT(SAT)
netic field is reduced below the release point (B
. When the mag-
), the
RP
device output goes high (turns OFF). The difference in the
magnetic operate and release points is the hysteresis (B
hys
of the device. This built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise.
Applications. It is strongly recommended that an
external bypass capacitor be connected (in close proximity
to the Hall sensor) between the supply and ground of the
device to reduce both external noise and noise generated
by the chopper-stabilization technique.
REG
& HOLD
SAMPLE
X
B
+V
Dwg. EH-012
—
HALL
VOLTAGE
+
DWG. FRD-903-2
+V
V
CC
OUTPUT VOLTAGE
B
RP
B
OP
)
V
OUT(SAT)
0
0
FLUX DENSITY
+B
Dwg. GH-007-2
Many other methods of operation are possible. Extensive applications information on magnets and Hall-effect
sensors is also available in the Allegro Electronic DataBook AMS-702 or Application Note 27701, or
The ATS535JSB and ATS535SSB operate points are
programmed by serially addressing the device through the
supply terminal (pin1). After the correct operate point is
determined, the device programming bits are selected and
then a “lock” set to prevent any further (accidental)
programming.
Program Enable. To program the device, a sequence of
pulses is used to activate/enable the addressing mode as
shown in figure 1. This sequence of a V
seven V
pulses, and a VPP pulse with no supply interrup-
PH
tions, is designed to prevent the device from being programmed accidentally (for example, as a result of noise on
the supply line).
pulse, at least
PP
V
PP
V
PH
V
PL
t
d(1)
0
PROGRAM ENABLE
(AT LEAST 7 PULSES)
t
d(1)
t
d(0)
Dwg. WH-013
Figure 1 — Program enable
PROGRAMMING PROTOCOL over operating temperature range.
Limits
CharacteristicSymbolDescriptionMin.Typ.Max.Units
Programming VoltageV
Programming CurrentI
Pulse Widtht
Pulse Rise Timet
Pulse Fall Timet
V
V
t
PH
PP
PP
d(0)
d(1)
t
dP
PL
r
f
NOTE: Typical data is at TA = +25°C and is for design information only.
Address Determination. The operate point is adjustable in 64 increments. With the appropriate target or gear*
in position, the 64 switch points are sequentially selected
(figure 2) until the required operate point is reached. Note
that the difference between the operate point and the
release point (hysteresis) is a constant for all addresses.
Set-Point Programming. After the desired set-point
address is determined (0 through 63), each bit of the
equivalent binary address is programmed individually. For
example, as illustrated in figure 3, to program address code
5 (binary 000101), bits 1 and 3 need to be programmed.
Each bit is programmed during the
wide V
Lock Programming. After the desired set point is
programmed, the program lock is then activated (figure 4)
to prevent further programming of the device.
pulse and is not reversible.
PP
ADDRESS N-2
ADDRESS 0
ADDRESS 1
V
PH
V
PL
0
ADDRESS 2
t
d(1)
ADDRESS N-1
ADDRESS N
t
d(0)
Dwg. WH-014
(UP TO 63)
Figure 2 — Address determination
V
PP
V
PH
V
PL
0
t
d(1)
PROGRAM ENABLE
t
d(1)
BIT 3 PROGRAM
t
d(0)
Figure 3 — Set-point programming
V
PP
V
PH
V
PL
0
t
PROGRAM ENABLELOCK PROGRAM
t
d(1)
d(1)
t
d(0)
Figure 4 — Lock programming
* In application, the terms “gear” and “target” are often
interchanged. However, “gear” is preferred when motion
is transferred.
devices require minimal protection circuitry during
operation from a low-voltage regulated line. The on-chip
voltage regulator provides immunity to power supply
variations between 4.25 V and 26 V. However, even while
operating from a regulated line, some supply and output
filtering is required to provide immunity to coupled and
injected noise on the supply line. A basic RC low-pass
circuit (R1C1) on the supply line and an optional output
capacitor (C2) is recommended for operation in noisy
environments. Because the device has an open-collector
output, an output pull-up resistor (RL) must be included
either at the sensor output (pin 2) or by the signal processor input.
SUPPLY
20 Ω
R
L
C
R
1
0.033 µF
1
Vcc
OUTPUT
C
100 pF
2
Operation From an Unregulated Power Supply. In
automotive applications, where the device receives its
power from an unregulated supply such as the battery, full
protection is generally required so that the device can
withstand the many supply-side transients. Specifications
for such transients vary between car manufacturers, and
protection-circuit design should be optimized for each
application. In the circuit below, a simple Zenercontrolled regulator is constructed using discrete components. The RC low-pass filter on the supply line (R1C1)
and a low-value supply bypass capacitor (CS) can be
included, if necessary, so as to minimize susceptibility to
EMI/RFI. The npn transistor should be chosen with
sufficiently high forward breakdown voltage so as to
withstand supply-side transients. The series diode should
be chosen with sufficiently high reverse breakdown
capabilities so as to withstand the most negative transient.
The current-limiting resistor (RZ) and the Zener diode
should be sized for power dissipation requirements.
* Temperature excursions to 225°C for 2 minutes or less are permitted.
† All industry-accepted soldering techniques are permitted for these subassemblies provided the indicated maximum temperature for
each component (e.g., sensor face, plastic housing) is not exceeded. Reasonable dwell times, which do not cause melting of the plastic
housing, should be used.
Sensor Location (in millimeters)
(sensor location relative to package center is the design objective)
Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such departures from the detail specifications as may be required
to permit improvements in the design of its products.
The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of
third parties which may result from its use.