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Package SH, 4-pin SIP
1
2
3
4
1. VCC
2. No connection (float or tie to VCC)
3. Test pin (float or tie to GND)
4. GND
ATS643LSH
Self-Calibrating, Zero-Speed Differential
Gear Tooth Sensor with Continuous Update
The ATS643 is an optimized combination of integrated circuit and magnet that
provides a manufacturer-friendly solution for true zero-speed digital gear-tooth
sensing in two-wire applications. The device consists of a single-shot molded
plastic package that includes a samarium cobalt magnet, a pole piece, and a
Hall-effect IC that has been optimized to the magnetic circuit and the automotive
environment. This small package can be easily assembled and used in conjunction
with a wide variety of gear shapes and sizes.
The integrated circuit incorporates a dual element Hall-effect sensor with signal
processing circuitry that switches in response to differential magnetic signals
created by rotating ferrous targets. The device contains a sophisticated compensating circuit to eliminate magnet and system offsets immediately at power-on.
Digital tracking of the analog signal is used to achieve true zero-speed operation,
while also setting the device switchpoints. The resulting switchpoints are air gap
independent, greatly improving output and duty cycle accuracy. The device also
uses a continuous update algorithm to fine-tune the switchpoints while in running
mode, maintaining the device specifications even through large changes in air gap
or temperature.
The regulated current output is configured for two-wire operation, offering inherent diagnostic information. This device is ideal for obtaining speed and duty cycle
information in gear-tooth based applications such as transmission speed sensing.
AB SO LUTE MAX I MUM RAT INGS
Supply Voltage, VCC..................See Power Derating
Reverse-Supply Voltage, V
Operating Temperature
Ambient, T
Maximum Junction, T
Storage Temperature, T
ATS643-DS, Rev. 1
................................ –40ºC to 150ºC
A
........................–18 V
RCC
........................165ºC
J(max)
.................. –65ºC to 170ºC
S
Features and Benefits
• Fully-optimized differential digital gear
tooth sensor
• Single chip-IC for high reliability
• Internal current regulator for 2-wire
operation
• Small mechanical size (8 mm diameter
x 5.5 mm depth)
• Switchpoints air gap independent
• Digital output representing gear profile
Use the following complete part numbers when ordering:
Part Number Package ICC Typical
ATS643LSH-I1 4-pin plastic SIP 6.0 Low to 14.0 High mA
ATS643LSH-I2 4-pin plastic SIP 7.0 Low to 14.0 High mA
• Precise duty cycle accuracy throughout temperature range
• Large operating air gaps
• <2 ms power-on time
• AGC and reference adjust circuit
• True zero-speed operation
• Undervoltage lockout
• Wide operating voltage range
• Defined power-on state
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Functional Block Diagram
VCC (Pin 1)
PDAC
NDAC
Hall AMP
Offset Adjust
ThresholdP
Reference
Generator
and
Updates
ThresholdN
AGC
Internal
Regulator
Threshold
Logic
GND (Pin 4)
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
OPERATING CHARACTERISTICS using reference target 60-0, TA and VCC within specification, unless otherwise noted
Characteristic Symbol Test Conditions Min. Typ. Max. Units
ELECTRICAL CHARACTERISTICS
Supply Voltage V
Undervoltage Lockout V
CC(UV) VCC
Supply Zener Clamp Voltage V
I
CC(Low)
Supply Current
I
CC(High)
I
Supply Current Ratio
CC(High)
I
CC(Low)
POWER-ON CHARACTERISTICS
Power-On State I
Power-On Time
1
CC(PO)
OUTPUT STAGE
Output Slew Rate
2
dI/dt R
Output State V
CC
t
on
OUT
Operating; TJ < 165 °C 4.0 – 24 V
0 → 5 V – 3.5 4.0 V
ICC = 19 mA for ATS643-I1, and 19.8 mA for
Z
ATS643-I2; TA = 25°C
28 – – V
ATS643-I1 4.0 6 8.0 mA
ATS643-I2 5.9 7 8.4 mA
ATS643-I1 12.0 14.0 16.0 mA
ATS643-I2 11.8 14.0 16.8 mA
/
Ratio of high current to low current 1.85 – 3.05 –
t < ton; dI/dt < 5 µs – High – mA
Target gear speed < 100 rpm – 1 2 ms
= 100 Ω, C
LOAD
R
on high side (VCC pin); ICC = I
SENSE
R
on low side (GND pin); ICC = I
SENSE
= 10 pF – 7 – mA/µs
LOAD
CC(High)
CC(High)
– Low – mV
– High – mV
Continued on the next page.
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
OPERATING CHARACTERISTICS (continued) using reference target 60-0, TA and VCC within specification, unless otherwise noted
Characteristic Symbol Test Conditions Min. Typ. Max. Units
SWITCHPOINT CHARACTERISTICS
Rotation Speed S
ROT
Reference Target 60-0 0 – 12,000 rpm
Bandwidth BW Equivalent to f – 3dB 25 40 – kHz
Operate Point B
Release Point B
CALIBRATION
3
Initial Calibration Period C
AGC Calibration Disable C
Start Mode Hysteresis PO
OP
RP
I
f
HYS
% of peak to peak referenced from PDAC to NDAC,
AG < AG
MAX
% of peak to peak referenced from PDAC to NDAC,
AG < AG
MAX
Quantity of rising output (current) edges required for
accurate edge detection
Quantity of rising output (current) edges used for
calibrating AGC
–65– %
–35– %
– – 3 Edge
– – 3 Edge
– 175 – mV
DAC CHARACTERISTICS
Dynamic Offset Cancellation – ±60 – G
Tracking Data Resolution
Quantity of bits available for PDAC/NDAC tracking of
both positive and negative signal peaks
–9–Bit
FUNCTIONAL CHARACTERISTICS
Air Gap Range
Maximum Operable Air Gap AG
4
AG ∆DC within specification 0.5 – 2.5 mm
(opmax)
Output switching (no missed edges); ∆DC not
guaranteed
– – 2.75 mm
Duty Cycle Variation ∆DC Wobble < 0.5 mm, AG within specification – – ±10 %
Input Signal Range Sig ∆DC within specification 40 – 1400 G
Minimum Operable Input Signal Sig
1
Power-On Time includes the time required to complete the internal automatic offset adjust. The DACs are then ready for peak acquisition.
2
dI is the difference between 10% of I
of the bypass capacitor, if one is used.
3
Continuous Update (calibration) functions continuously during Running mode operation.
4
AG is dependent on the available magnetic field. The available field is dependent on target geometry and material, and should be independently
characterized. The field available from the reference target is given in the reference target parameter section of the datasheet.
ATS643-DS, Rev. 1
CC(Low)
(opmin)
and 90% of I
Output switching (no missed edges); ∆DC not
guaranteed
, and dt is time period between those two points. Note: dI/dt is dependent upon the value
CC(High)
30 – – G
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
ATS643LSH
Reference Gear Magnetic P rofile
Two Tooth-to-Valley Transitions
-700
-600
-500
-400
-300
-200
-100
0
100
200
300
400
500
600
700
0123456789101112
AG (mm)
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
REFERENCE TARGET, 60-0 (60 Tooth Target)
Characteristics Symbol Test Conditions Typ. Units Symbol Key
Outside Diameter D
Face Width F
Circular Tooth Length t
Circular Valley Length t
Tooth Whole Depth h
Outside diameter of target
o
Breadth of tooth, with respect
to sensor
Length of tooth, with respect
to sensor; measured at D
Length of valley, with respect
v
to sensor; measured at D
t
120 mm
6mm
3mm
o
3mm
o
3mm
Material Low Carbon Steel – –
Peak-to-Peak Differential B* (G)
Reference Gear Magnetic Gradient Amplitude
1800
1600
1400
1200
1000
800
600
400
200
0
0.5 1 1.5 2 2.5
with Reference to Air Gap
Branded Face
of Sensor
Reference Target
60-0
Differential B* (G)
Gear Rotation (°)
*Differential B corresponds to the calculated difference in the magnetic fi eld as
sensed simultaneously at the two Hall elements in the device (B
= BE1 – BE2).
DIFF
ATS643-DS, Rev. 1
2.00 mm AG
0.50 mm AG
AG (mm)
0.50
0.75
1.00
1.25
1.50
1.75
2.00
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
ATS643LSH
40
45
50
55
60
–50 0 50 100 150 200
TA(°C)
Duty Cycle at 1000
RPM
40
45
50
55
60
00.511.522.533.5
AG (mm)
Duty Cycle (%)
-40
0
25
85
150
Duty Cycle (25°C)
40
45
50
55
60
0 500 1000 1500 2000 2500
RPM
Duty Cycle (%)
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Characteristic Data
Data taken from 3 lots, 30 pieces/lot; I1 trim
Reference Target 60-0
Duty Cycle at 1000 RPM
AG (mm)
3.0
2.75
2.5
2.25
2.0
1.5
1.0
0.5
Duty Cycle (%)
AG (mm)
2.75
2.25
TA(ºC)
3.0
2.5
2.0
1.5
1.0
0.5
Continued on the next page.
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
6
ATS643LSH
I
CC (Low)
3
4
5
6
7
8
9
–50 0 50 100 150 200
I
cc
(mA)
I
CC(Low)
3
4
5
6
7
8
9
0 5 10 15 20 25 30
Vcc(V)
Icc (mA)
I
CC(High)
11
12
13
14
15
16
17
–50 0 50 100 150 200
TA(°C)
I
cc
(mA)
26.5V
20V
12V
4V
I
CC(High)
11
12
13
14
15
16
17
0 5 10 15 20 25 30
Vcc(V)
Icc (mA)
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Characteristic Data (continued)
Data taken from 3 lots, 30 pieces/lot; I1 trim
V
CC
26.5
20.0
12.0
4.0
TA(°C)
TA(ºC)
150
–40
85
25
0
Output current in relation to sensed magnetic flux density. Transition through B
ATS643-DS, Rev. 1
must precede by transition through B
V
CC
26.5
20.0
12.0
4.0
Hysteresis of ∆I
ICC
TA(ºC)
150
–40
85
25
0
Switching Due to ∆B
I+
I
CC(High)
RP
OP
Switch to Low
CC
.
I
Switch to High
I
CC(Low)
B
RP
B
HYS
B+
OP
B
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
7
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Symbol Test Conditions Min. Typ. Max Units
Package Thermal Resistance
Minimum-K PCB (single-sided with copper limited to
R
θJA
solder pads)
Low-K PCB (single-sided with copper limited to solder
pads and 3.57 in.2 (23.03 cm2) of copper area)
Power Derating Curve
T
= 165ºC; ICC=I
25
24
23
22
21
(V)
20
CC
19
18
17
16
15
14
13
12
11
10
9
Maximum Allowable V
8
7
6
5
4
3
2
20 40 60 80 100 120 140 160 180
J(max)
Low-K PCB
(R
= 84 ºC/W)
θJA
Minimum-K PCB
(R
= 126 ºC/W)
θJA
CC(max)
V
CC(max)
V
CC(min)
126 – – ºC/W
84 – – ºC/W
ATS643-DS, Rev. 1
Maximum Power Dissipation, P
1900
J(max)
CC(max);ICC=ICC(max)
T
= 165ºC; VCC=V
1800
1700
1600
1500
1400
1300
θJA
=126ºC/W)
Low-K PCB
(
R
θJA
= 84 ºC/W)
(mW)
D
1200
1100
1000
900
800
Minimum-K PCB
(R
700
600
500
400
Power Diss ipation, P
300
200
100
0
20 40 60 80 100 120 140 160 180
Temperature (°C)
D(max)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
8
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Functional Description
Sensing Technology. The ATS643 module contains a
single-chip differential Hall effect sensor IC, a samarium cobalt
magnet, and a flat ferrous pole piece (concentrator). As shown
in figure 1, the Hall IC supports two Hall elements, which sense
the magnetic profile of the ferrous gear target simultaneously,
but at different points (spaced at a 2.2 mm pitch), generating a
differential internal analog voltage (V
) that is processed for
PROC
precise switching of the digital output signal.
The Hall IC is self-calibrating and also possesses a temperature compensated amplifier and offset cancellation circuitry. Its
voltage regulator provides supply noise rejection throughout the
operating voltage range. Changes in temperature do not greatly
affect this device due to the stable amplifier design and the offset
rejection circuitry. The Hall transducers and signal processing
electronics are integrated on the same silicon substrate, using a
proprietary BiCMOS process.
Target Profiling During Operation. When proper power is
applied to the sensor, it is capable of providing digital information that is representative of the mechanical features of a rotating
gear. The waveform diagram in figure 3 presents the automatic
translation of the mechanical profile, through the magnetic
profile that it induces, to the digital output signal of the ATS643.
No additional optimization is needed and minimal processing
circuitry is required. This ease of use reduces design time and
incremental assembly costs for most applications.
Determining Output Signal Polarity. In figure 3, the top
panel, labeled Mechanical Position, represents the mechanical features of the target gear and orientation to the device. The
bottom panel, labeled Sensor Output Signal, displays the square
waveform corresponding to the digital output signal that results
from a rotating gear configured as shown in figure 2. That direction of rotation (of the gear side adjacent to the face of the sensor)
is: perpendicular to the leads, across the face of the device, from
the pin 1 side to the pin 4 side. This results in the sensor output
switching from low, I
CC(Low)
, to high, I
CC(High)
, as the leading
edge of a tooth (a rising mechanical edge, as detected by the
sensor) passes the sensor face. In this configuration, the device
output current switches to its high polarity when a tooth is the
target feature nearest to the sensor. If the direction of rotation is
reversed, so that the gear rotates from the pin 4 side to the pin 1
side, then the output polarity inverts. That is, the output signal
goes high when a falling edge is detected, and a valley is the
nearest to the sensor. Note, however, that the polarity of I
depends on the position of the sense resistor, R
SENSE
(see Operat-
OUT
ing Characteristics table).
Continuous Update of Switchpoints. Switchpoints are the
threshold levels of the differential internal analog signal, V
PROC
,
at which the device changes output signal polarity. The value of
Target (Gear)
Element Pitch
Hall Element 2
Dual-Element
Hall Effect Device
Figure 1. Relative motion of the target is detected by the dual Hall elements mounted on the Hall IC.
Rotating Target
Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation
results in a high output signal when a tooth of the target gear is nearest
the face of the sensor (see figure 3). A right-to-left (pin 4 to pin 1) rotation inverts the output signal polarity.
South Pole
North Pole
Hall Element 1
Hall IC
Pole Piece
(Concentrator)
Back-biasing Magnet
Case
(Pin 1 Side)(Pin n >1 Side)
1
4
Branded Face
of Sensor
Mechanical Position (Target movement pin 1 to pin 4)
This tooth
sensed
earlier
Target Magnetic Profile
+B
Sensor Orientation to Target
Pin 4
Side
Sensor Internal Differential Analog Signal, V
B
OP(#1)
Sensor Internal Switch State
Sensor Output Signal, I
Figure 3. The magnetic profile reflects the geometry of the target, allowing the ATS643 to present an accurate digital output response.
Target
(Gear)
Sensor Branded Face
Sensor
B
OP(#2)
B
RP(#1)
On OffOff On
OUT
Pin 1
Side
PROC
This tooth
sensed
later
+t
+t
+t
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
9
ATS643LSH
B
HYS(#1)
Pk
(#4)
Pk
(#5)
Pk
(#7)
Pk
(#9)
Pk
(#2)
Pk
(#3)
Pk
(#1)
Pk
(#6)
Pk
(#8)
V
PROC
(V)
B
RP(#1)
B
OP(#1)
B
RP(#2)
B
RP(#3)
B
OP(#3)
B
RP(#4)
B
OP(#4)
B
HYS(#4)
B
HYS(#3)
B
HYS(#2)
t+
V+
B
OP(#2)
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
V
is directly proportional to the magnetic flux density, B,
PROC
induced by the target and sensed by the Hall elements. When
V
transitions through a switchpoint from the appropriate
PROC
higher or lower level, it triggers sensor switch turn-on and turnoff. As shown in figure 3, when the switch is in the off state, as
rises through a certain limit, referred to as the operate
V
PROC
point, B
in the on state, as V
, the switch toggles from off to on. When the switch is
OP
falls below BOP to a certain limit, the
PROC
release point, B
, the switch toggles from on to off.
RP
As shown in panel C of figure 4, threshold levels for the ATS643
switchpoints are established dynamically as function of the
peak input signal levels. The ATS643 incorporates an algorithm
that continuously monitors the system and updates the switching thresholds accordingly. The switchpoint for each edge is
determined by the detection of the previous two edges. In this
manner, variations are tracked in real time.
B
HYS
1
2
3
4
(A) TEAG varying; cases such as
eccentric mount, out-of-round region,
normal operation position shift
Sensor
Switchpoint
B
OP(#1)
B
RP(#1)
B
OP(#2)
B
RP(#2)
B
OP(#3)
B
RP(#3)
B
OP(#4)
B
RP(#4)
Target
Smaller
TEAG
(C) Referencing the internal analog signal, V
Determinant
Peak Values
Pk
(#1)
Pk
(#2)
Pk
(#3)
Pk
(#4)
Pk
(#5)
Pk
(#6)
Pk
(#7)
Pk
(#8)
, Pk
, Pk
, Pk
, Pk
, Pk
, Pk
, Pk
, Pk
(#2)
(#3)
(#4)
(#5)
(#6)
(#7)
(#8)
(#9)
Sensor
Target
Larger
TEAG
(B) Internal analog signal, V
typically resulting in the sensor
V+
Smaller
TEAG
Larger
TEAG
(V)
PROC
V
(Delimited by switchpoints)
0
Target Rotation (°)
, to continuously update device response
PROC
PROC
Hysteresis Band
,
Smaller
TEAG
360
Figure 4. The Continuous Update algorithm allows the Allegro sensor to immediately interpret and adapt to significant variances in the magnetic field
generated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and
similar dynamic application problems that affect the TEAG (Total Effective Air Gap). The algorithm is used to dynamically establish and subsequently
update the device switchpoints (BOP and BRP). The hysteresis, B
it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, V
As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the sensor as a varying magnetic field, which
results in proportional changes in the internal analog signal, V
switchpoints based on the fluctuation of V
ATS643-DS, Rev. 1
, as shown in panel C.
PROC
PROC
, at each target feature configuration results from this recalibration, ensuring that
HYS(#x)
PROC
.
, shown in panel B. The Continuous Update algorithm is used to establish accurate
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
10
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Power-On State Operation. The ATS643 is guaranteed to
power-on in the high current state, I
CC(High)
.
Initial Edge Detection. The device self-calibrates using the
initial teeth sensed, and then enters Running mode. This results
in reduced accuracy for a brief period (less than four teeth),
Target
(Gear)
Sensor Position
Power-on
over valley
Start Mode
Hysteresis
Overcome
Power-on
at rising edge
1 3 42
1
V
PROC
Output
AGC Calibration Running Mode
V
PROC
2
however, it allows the device to optimize for continuous update
yielding adaptive sensing during Running mode. As shown in
figure 5, the first three high peak signals are used to calibrate
AGC. However, there is a slight variance in the duration of initialization, depending on what target feature is nearest the sensor
when power-on occurs.
Output
Start Mode
Hysteresis
Overcome
V
AGC Calibration
PROC
Running Mode
Power-on
over tooth
3
Output
Start Mode
Hysteresis
Overcome
V
AGC Calibration
PROC
Running Mode
Power-on
at falling edge
4
Output
Start Mode
Hysteresis
Overcome
Figure 5. Power-on initial edge detection. This figure demonstrates four typical power-on scenarios. All of these examples assume that the target is
moving relative to the sensor in the direction indicated. The length of time required to overcome Start Mode Hysteresis, as well as the combined effect
of whether it is overcome in a positive or negative direction plus whether the next edge is in that same or opposite polarity, affect the point in time when
AGC calibration begins. Three high peaks are always required for AGC calibration.
AGC Calibration
Running Mode
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
11
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Start Mode Hysteresis. This feature helps to ensure optimal
self-calibration by rejecting electrical noise and low-amplitude
target vibration during initialization. This prevents AGC from
calibrating the sensor on such spurious signals. Calibration can
be performed using the actual target features.
Target, Gear
Sensor Position Relative to Target
Target Magnetic Profile
Differential Signal, V
Start Mode Hysteresis, PO
PROC
1 2
HYS
A typical scenario is shown in figure 6. The hysteresis, PO
HYS
,
is a minimum level of the peak-to-peak amplitude of the internal
analog electrical signal, V
, that must be exceeded before the
PROC
ATS643 starts to compute switchpoints.
5
B
RP(#1)
B
OP(#1)
B
OP(#2)
1
Output Signal, I
Figure 6. Operation of Start Mode Hysteresis
Position 1. At power-on, the ATS643 begins sampling V
Position 2. At the point where the Start Mode Hysteresis is exceeded, the device begins to establish switching thresholds (BOP and BRP) using the Continuous Update algorithm. After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid V
Hysteresis can be generated either by a legitimate target feature or by excessive vibration.
Position 3. In this example, the first switchpoint transition is through B
If the first switchpoint transition had been through BRP (such as position 4), no output transition would occur because I
polarity. The first transition would occur at position 5 (BOP).
ATS643-DS, Rev. 1
OUT
PROC
.
2
3
. and the output transitions from high to low.
OP
4
5
value exceeding the Start Mode
PROC
already would be in the high
OUT
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
12
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Undervoltage Lockout. When the supply voltage falls
below the minimum operating voltage, V
, ICC goes high
CC(UV)
and remains high regardless of the state of the magnetic gradient from the target. This lockout feature prevents false signals,
caused by undervoltage conditions, from propagating to the
output of the sensor.
Power Supply Protection. The device contains an on-chip
regulator and can operate over a wide VCC range. For devices
that need to operate from an unregulated power supply, transient
protection must be added externally. For applications using a
regulated line, EMI/RFI protection may still be required. Contact
Allegro Microsystems for information on the circuitry needed
for compliance with various EMC specifications. Refer to figure 7 for an example of a basic application circuit.
Automatic Gain Control (AGC). This feature allows the
device to operate with an optimal internal electrical signal,
regardless of the air gap (within the AG specification). At
(Optional)
1
VCC
power-on, the device determines the peak-to-peak amplitude
of the signal generated by the target. The gain of the sensor is
then automatically adjusted. Figure 8 illustrates the effect of this
feature.
Automatic Offset Adjust (AOA). The AOA is patented circuitry that automatically cancels the effects of chip, magnet, and
installation offsets. (For capability, see Dynamic Offset Cancellation, in the Operating Characteristics table.) This circuitry is
continuously active, including both during power-on mode and
running mode, compensating for any offset drift. Continuous
operation also allows it to compensate for offsets induced by
temperature variations over time.
Assembly Description. The ATS643 is integrally molded
into a plastic body that has been optimized for size, ease of
assembly, and manufacturability. High operating temperature
materials are used in all aspects of construction.
Ferrous Target
Mechanical Profile
V+
Internal Differential
Analog Signal
Response, without AGC
AG
Large
2
ATS643
Figure 7. Typical basic circuit for proper device operation.
ATS643-DS, Rev. 1
4
100 Ω
3
0.01 µF
(Optional)
AG
Small
V+
Internal Differential
Analog Signal
Response, with AGC
Figure 8. Automatic Gain Control (AGC). The AGC function corrects for
variances in the air gap. Differences in the air gap cause differences in
the magnetic field at the device, but AGC prevents that from affecting
device performance, a shown in the lowest panel.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
AG
Small
AG
Large
13
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Power Derating
The device must be operated below the maximum junction
temperature of the device, T
. Under certain combinations of
J(max)
peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the
application. This section presents a procedure for correlating
factors affecting operating TJ. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, R
, is a figure of merit sum-
θJA
marizing the ability of the application and the device to dissipate
heat from the junction (die), through all paths to the ambient air.
Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, R
relatively small component of R
. Ambient air temperature,
θJA
θJC
, is
TA, and air motion are significant external factors, damped by
overmolding.
The effect of varying power levels (Power Dissipation, PD), can
be estimated. The following formulas represent the fundamental
relationships used to estimate TJ, at PD.
PD = VIN × I
∆T = PD × R
IN
(2)
θJA
(1)
Example: Reliability for V
at TA = 150°C, package L-I1, using
CC
minimum-K PCB
Observe the worst-case ratings for the device, specifically:
R
126°C/W, T
θJA =
I
CC(max) = 16
mA.
Calculate the maximum allowable power level, P
J(max) =
165°C, V
CC(max) = 24
V, and
D(max)
. First,
invert equation 3:
∆T
max
= T
– TA = 165 °C – 150 °C = 15 °C
J(max)
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
P
D(max)
= ∆T
max
÷ R
= 15°C ÷ 126 °C/W = 119 mW
θJA
Finally, invert equation 1 with respect to voltage:
V
CC(est)
= P
D(max)
÷ I
= 119 mW ÷ 16 mA = 7 V
CC(max)
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤V
Compare V
able operation between V
R
. If V
θJA
V
is reliable under these conditions.
CC(max)
CC(est)
CC(est)
to V
≥ V
. If V
CC(max)
CC(est)
CC(max)
CC(est)
and V
CC(max)
, then operation between V
≤ V
CC(max)
requires enhanced
.
CC(est)
, then reli-
CC(est)
and
T
= TA + ∆T (3)
J
For example, given common conditions such as: TA= 25°C,
V
= 12 V, I
CC
P
= VCC × I
D
∆T = PD × R
= 4 mA, and R
CC
= 12 V × 4 mA = 48 mW
CC
= 48 mW × 140 °C/W = 7°C
θJA
θJA
= 140 °C/W, then:
TJ = TA + ∆T = 25°C + 7°C = 32°C
A worst-case estimate, P
able power level (V
at a selected R
θJA
CC(max)
and TA.
, represents the maximum allow-
D(max)
, I
), without exceeding T
CC(max)
J(max)
,
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
14
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
Package SH, 4-pin SIP
5.5 .217
C
8.0 .315
B
5.8 .228
2.9 .114
20.95 .825
5.0 .244
13.05 .514
4.0 .157
A
1 .039
1.27 .050
0.6
1.7 .067
.024
A
B
C
D
2431
A
Dimensions in millimeters. Untoleranced dimensions are nominal.
U.S. Customary dimensions (in.) in brackets, for reference only
Dambar removal protrusion
Metallic protrusion, electrically connected to pin 4 and substrate (both sides)
Active Area Depth 0.43 mm [.017]
Thermoplastic Molded Lead Bar for alignment during shipment
0.38 .015
1.08 .043
D
ATS643-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
15
ATS643LSH
Self-Calibrating, Zero-Speed Differential GTS with Continuous Update
ATS643-DS, Rev. 1
The products described herein are manufactured under one
or more of the following U.S. patents: 5,045,920; 5,264,783;
5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319;
5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other
patents pending.
Allegro MicroSystems, Inc. reserves the right to make, from time
to time, such de par tures from the detail spec i fi ca tions as may be
required to permit improvements in the per for mance, reliability,
or manufacturability of its products. Before placing an order, the
user is cautioned to verify that the information being relied upon is
current.
Allegro products are not authorized for use as critical components in life-support devices or sys tems without express written
approval.
The in for ma tion in clud ed herein is believed to be ac cu rate and
reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other
rights of third parties which may result from its use.
Copyright © 2004 Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
16
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