FEATURES AND BENEFITS
• Three-wire back-biased speed sensor optimized for
transmission speed-sensing applications
• Integrated in-package EMC protection circuit allows
compliance to most Automotive EMC environments
without external circuitry
• Small-signal lockout for immunity to vibration
• Tight timing accuracy over full operating temperature
range
• True zero-speed operation
• Air gap independent switchpoints
• Large operating air gaps achieved through use of gain
and offset adjust circuitry
• Wide operating voltage range with undervoltage lockout
(UVLO)
• Digital output representing target profile
• Single-chip sensing IC for high reliability
• High-speed startup
DESCRIPTION
The ATS668LSM is an optimized Hall-effect integrated circuit
(IC) and permanent magnet pellet combination with integrated
EMC protection components to provide a user-friendly solution
for true zero-speed digital gear tooth sensing. The small package
can be easily assembled and used in conjunction with a wide
variety of gear tooth sensing applications.
The device incorporates a dual element Hall IC that switches
in response to differential magnetic signals created by
a ferromagnetic target. The IC contains a sophisticated
compensating circuit designed to eliminate the detrimental
effects of magnet and system offsets. Digital processing of the
analog signal provides zero-speed performance independent of
air gap and also dynamic adaptation of device performance to the
typical operating conditions found in automotive applications
(i.e. vibration immunity and runout tolerance). High-resolution
peak detecting DACs are used to set the adaptive switching
thresholds of the device. Hysteresis in the thresholds reduces
the negative effects of any anomalies in the magnetic signal
associated with system or target anomalies typically seen in
many automotive applications.
This device is available in a lead (Pb) free 3-pin SIP package
(SM) with matte-tin leadframe plating.
ATS668LSM-DS, Rev. 2
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
PACKAGE: 3-pin SIP (suffix SM)
Functional Block Diagram
Not to scale
ATS668LSM
Package
Die
Hall Amp
Offset
Adjust AGC
PDAC
NDAC
+
-
Control Logic and Threshold Generator
+
-
Output
Control
VCC
VOUT
GND
Threshold
Comparators
R
SUPPLY
R
OUT
C
OUT
C
SUPPLY
April 24, 2017
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
2
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
SELECTION GUIDE
Part Number Package
ATS668LSMTN-T 3-pin SIP with matte-tin leadframe plating
*Contact Allegro™ marketing or your local sales representative for additional options.
RoHS
COMPLIANT
ABSOLUTE MAXIMUM RATINGS
Characteristic Symbol Notes Rating Units
Supply Voltage VCC 26.5 V
Reverse Supply Voltage VRCC –18 V
Reverse Supply Current IRCC 50 mA
Reverse Output Voltage VROUT -0.5 V
Output Sink Current IOUT 25 mA
Operating Ambient Temperature TARange L, refer to Power Derating Curve –40 to 150 °C
Maximum Junction Temperature TJ(max) 165 °C
Storage Temperature Tstg –65 to 170 °C
INTERNAL PASSIVE COMPONENTS RATINGS
Symbol Characteristic Rating Unit
CSUPPLY Rated Nominal Capacitance 220 nF
COUT Rated Nominal Capacitance 1.8 nF
RSUPPLY Rated Nominal Resistance 50 Ω
ROUT Rated Nominal Resistance 50 Ω
Terminal List Table
Number Name Function
1 VCC Supply voltage
2 GND Ground
3 VOUT Device output
Pinout Diagram
Figure 1: Typical Application
2 31
ATS668SM
GND
RSUPPLY ROUT
RPU
V
CC
VOUT
COUT
V
CC
CSUPPLY
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
3
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
OPERATING CHARACTERISTICS: Valid throughout full operating and temperature ranges, using Reference Target 60-0, unless
otherwise noted.
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
ELECTRICAL CHARACTERISTICS
Supply Voltage VCC Operating, TJ < TJ
(max) 4.6 – 24 V
Undervoltage Lockout VUVLO – 4.1 4.55 V
Reverse Supply Current IRCC VCC = –18 V – – –10 mA
Supply Current ICC – – 12 mA
Supply Zener Clamp Voltage VZICC = ICC(MAX) + 3 mA 28.0 – – V
Supply Zener Current IZTJ < TJ
(max), VCC = 27 V – – 15 mA
Reverse Supply Zener Clamp Voltage VRZ ICC = –3 mA, TA = 25°C – – –18 V
OUTPUT STAGE
Low Output Voltage VSAT ISINK = 10 mA, Output = ON – 750 1000 mV
Output Zener Clamp Voltage VZOUT IOUT = 3 mA, TA = 25°C 28.0 – – V
Output Current Limit ILIM VOUT = 12 V, TJ < TJ
(max) 25 45 70 mA
Output Leakage Current IOFF VOUT = 24 V, Output = off state (VOUT = High) – – 10 µA
Output Rise Time trRPU = 1 kΩ, VPU = 5 V –4–μs
Output Fall Time tf–6–μs
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
4
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
MAGNETIC CHARACTERISTICS
Characteristics Symbol Note Min. Typ. Max. Unit
MAGNETIC CHARACTERISTICS
Allowable Differential Signal
Reduction
Bseq(min)/
Bseq(max)
Over 60 cycles, see Figure 2 0.5 – – –
Bseq(n+1)/
Bseq(n)
Single cycle-to-cycle variation 0.6 – – –
Figure 2: Differential Sequential Signal Variation Figure 3: Sequential Pulse Variation
BSEQ(n+1)
BSEQ(n)
Sequential
Region
Ferromagnetic
Target
BSEQ(min)
BSEQ(max)
Tooth
Valley
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
5
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
FUNCTIONAL CHARACTERISTICS
Characteristics Symbol Note Min. Typ. Max. Unit
POWER ON
Power-On State POS VOUT state at t > tPO
; see Figure 1 – High – –
Power-On Time [1] tPO fop < 100 Hz – – 2 ms
AIR GAP
Operating Air Gap Range Guaranteed to operate within specification 0.5 – 2.5 mm
Extended Air Gap Range Switching only—not guaranteed to operate
within spec 2.5 – 3 mm
OFFSET
Dynamic Offset Cancellation BDIFFEXT Allowable user-induced offset ±60 – – G
CALIBRATION
Initial Calibration [2] CALI
Quantity of rising output edges required for
accurate edge detection – 2 3 edge
SWITCHING
Operating Speed fOP 0 – 12 kHz
Analog Signal Bandwidth BW 15 20 – kHz
Operate Point OP – 70 – %
Release Point RP – 30 – %
OUTPUT DUTY CYCLE [3]
Output Duty Cycle DC AG = 0.5 mm to 2.5 mm, Pin 3 to 1 target rotation 39 – 52 %
AG = 2.5 mm to 3.0 mm, Pin 3 to 1 target rotation 39 – 56 %
1 Power-On Time includes the time required to complete the internal automatic offset adjust. DAC is then ready for peak acquisition.
2 For power-on frequency, fOP < 200 Hz. Higher power-on frequencies may result in more input magnetic cycles until full output edge accuracy is
achieved, including the possibility of missed output edges.
3 Measured at fOP = 2 kHz. Output rise and fall times should be considered when measuring duty cycle.
Figure 4: Denition of Terms for Switchpoints
Differential Magnetic
Flux Density, B
DIFF
(G)
ValleyTooth
Forward
Reverse
+B
–B
Differential Processed
Signal, V
Proc
(V)
+V
–V
t
B
OP(FWD)
b
V
PROC(BOP)
V
PROC(BRP)
B
RP(FWD)
B
OP
%B
RP
%
100 %
B
OP(REV)
b
B
RP(REV)
Sensed Edgea
aSensed Edge: leading (rising) mechanical edge in forward rotation, trailing (falling) mechanical edge in reverse rotation
b
B
OP(FWD)
triggers the output transition during forward rotation, and B
OP(REV)
triggers the output transition during reverse rotation
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
6
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Reference Target 60-0 (60 Tooth Target)
Characteristics Symbol Test Conditions Typ. Units Symbol Key
Outside Diameter DOOutside diameter of target 120 mm Doht
F
Air Gap
Branded Face of Package
t
tv
Face Width F Breadth of tooth, with respect
to sensor IC 6 mm
Circular Tooth Length tLength of tooth, with respect
to sensor IC; measured at DO
3 degrees
Circular Valley Width tv
Length of valley, with respect
to sensor IC; measured at DO
3 degrees
Tooth Whole Depth ht3 mm
Material Low Carbon Steel – –
Figure 5: Reference Target Measurement Setup
Reference Target
60-0
of Sensor
Branded Face
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
7
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
POWER DERATING
THERMAL CHARACTERISTICS: May require derating at maximum conditions, see Power Derating section
Characteristic Symbol Test Conditions* Value Unit
Package Thermal Resistance RθJA Single layer PCB, with copper limited to solder pads 147 °C/W
*Additional thermal information available on the Allegro website
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
20 40 60 80 100120 140160 180
Maximum Allowable V
CC
(V)
Temperature (°C)
Power Derating Curve
1-layer PCB, Package SM
(RθJA = 147 °C/W)
VCC(max)
VCC(min)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
20 40 60 80 100120 140160 180
Power Dissipation, PD(mW)
Temperature (°C)
Power Dissipation versus Ambient Temperature
1-layer PCB, Package SM
(RθJA = 147 °C/W)
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
8
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
CHARACTERISTIC DATA
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
-50 0 50 100 150
ICC (mA)
TA(°C)
Supply Current versus Ambient Temperature
VCC: 24 V
VCC: 12 V
VCC: 4.6 V
0
100
200
300
400
500
600
700
800
900
1000
-50 0 50 100 150
VSAT (mV)
TA(°C)
Output Voltage versus Ambient Temperature
ISINK = 10 mA
40
44
48
52
56
60
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Duty Cycle (%)
Air Gap (mm)
Average Duty Cycle versus Air Gap
Pin 1 to 3 Rotation of Allegro Standard Target
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
9
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
FUNCTIONAL DESCRIPTION
Sensing Technology
The ATS668 contains a single-chip differential Hall-effect sensor
IC and a back-biasing pellet. The Hall IC supports a pair of Hall
elements which sense the magnetic profile of the ferromagnetic
gear target simultaneously, but at different points (spaced at a
2.2 mm pitch), generating a differential internal analog volt-
age, VPROC, that is processed for precise switching of the digital
output signal. The ATS668 is intended for use with ferromagnetic
targets.
The Hall IC is self-calibrating and also possesses a tempera-
ture 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
compensation circuitry. The Hall transducers and signal process-
ing electronics are integrated on the same silicon substrate, using
a proprietary BiCMOS process
Target Profiling During Operation
An operating device is capable of providing digital information
that is representative of the mechanical features of a rotating
gear. The waveform diagram in Figure 7 presents the automatic
translation of the mechanical profile, through the magnetic profile
that it induces, to the digital output signal of the IC. No addi-
tional 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 7, the top panel, labeled Mechanical Position, repre-
sents the mechanical features of the target gear and orientation to
the device. The bottom panel, labeled IC Output Signal, displays
the square waveform corresponding to the digital output signal
that results from a rotating gear configured as shown in Figure 6
and electrically connected as in Figure 1. That direction of rota-
tion (of the gear side adjacent to the package face) is: perpen-
dicular to the leads, across the face of the device, from the pin 1
side to the pin 3 side. This results in the IC output switching from
low state to high state as the leading edge of a tooth (a rising
mechanical edge, as detected by the IC) passes the package face.
In this configuration, the device output switches to its high polar-
ity when a tooth is the target feature nearest to the package. If the
direction of rotation is reversed, so that the gear rotates from the
pin 3 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 nearest to the package.
B
OP(#1)
B
RP(#1)
B
RP(#2)
B
OP(#2)
On OffOff On
IC Internal Switch State
Package Orientation to Target
IC Internal Differential Analog Signal, V
PROC
Mechanical Position (Target movement pin 1 to pin 3)
IC Output Signal, V
OUT
Target
(Gear)
(Package Top View)
Sensor Branded Face
Pin 1
Side
Pin 3
Side
Branded Face Hall Element Pitch
Target Magnetic Profile
+B
This tooth
sensed earlier
This tooth
sensed later
Back-Biasing
Pellet
IC
Rotation from pin 1 to pin 3
Pin 1 Pin 3
Rotating Target
(Ferromagnetic)
Rotating Target
(Ferromagnetic)
Rotation from pin 3 to pin 1
Pin 1 Pin 3
Branded Face
of SM Package
Branded Face
of SM Package
Figure 6: Sensor and target conguration. The output
is low when a tooth of the target gear is nearest the
branded face of the package.
Figure 7: The magnetic prole reects the features of
the target, allowing the sensor IC to present an accu-
rate digital representation of the target teeth.
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
10
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Undervoltage Lockout
When the supply voltage falls below the undervoltage lockout
voltage, VCC(min), the device enters Reset, where the output state
returns to the Power-On State (POS) until sufficient VCC is sup-
plied. This lockout feature prevents false signals, caused by under-
voltage conditions, from propagating to the output of the IC.
Power Supply Protection
The device contains an on-chip regulator and can operate over a
wide VCC range. The device also includes integrated in-package
EMC protection components virtually eliminating the need for
additional external passive components.
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 speci-
fication). At power-on, the device determines the peak-to-peak
amplitude of the signal generated by the target. The gain of the
IC is then automatically adjusted. Figure 8 illustrates the effect of
this feature.
Automatic Offset Adjust (AOA)
The AOA circuitry automatically compensates for the effects of
chip, magnet, and installation offsets. This circuitry is continu-
ously active, including during both power-on mode and running
mode, compensating for any offset drift (within the Allowable
User-Induced Differential Offset). Continuous operation also
allows it to compensate for offsets induced by temperature varia-
tions over time.
Running Mode Lockout
The ATS668 has a running mode lockout feature to prevent
switching in response to small signals that are characteristic
of vibration signals. The internal logic of the chip considers
small-signal amplitudes below a certain level to be vibration. The
output is held to the state prior to lockout until the amplitude of
the signal returns to normal operational levels.
Watchdog
The ATS668 employs a watchdog circuit to prevent extended loss
of output switching during sudden impulses and vibration in the
system. If the system changes the magnetic input drastically such
that target feature detection is terminated, the device will fully
reset itself, allowing the chip to recalibrate properly on the new
magnetic input signal.
Assembly Description
The ATS668 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 con-
struction.
Mechanical Profile
AG
Small
AG
Large
AG
Small
AG
Large
Internal Differential
Analog Signal
Response, with AGC
Internal Differential
Analog Signal
Response, without AGC
Ferrous Target
V+
V+
Figure 8: Automatic Gain Control (AGC). The AGC
function corrects for variances in the air gap. Differ-
ences in the air gap cause differences in the magnetic
eld at the device, but AGC prevents that from affect-
ing device performance, as shown in the lowest panel.
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
11
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
The device must be operated below the maximum junction
temperature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied
power or improving the heat dissipation properties of the appli-
cation. This section presents a procedure for correlating factors
affecting operating TJ. (Thermal data is also available on the
Allegro website.)
The Package Thermal Resistance, RθJA, is a figure of merit sum-
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, RθJC, is relatively
small component of RθJA. Ambient air temperature, 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 × IIN (1)
ΔT = PD × RθJA (2)
TJ = TA + ΔT (3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 6.5 mA, and RθJA = 147°C/W, then:
PD = VCC × ICC = 12 V × 6.5 mA = 78 mW
ΔT = PD × RθJA = 78 mW × 147°C/W = 11.5°C
TJ = TA + ΔT = 25°C + 11.5°C = 36.5°C
A worst-case estimate, PD(max), represents the maximum allow-
able power level (VCC(max), ICC(max)), without exceeding
TJ(max), at a selected RθJA and TA.
Example: Reliability for VCC at TA
=
150°C.
Observe the worst-case ratings for the device, specifically:
RθJA
=
147°C/W, TJ(max) =
165°C, VCC(max)
= 24 V, and
ICC(max) = 12
mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔTmax = TJ(max) – TA = 165°C
–
150°C = 15
°C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = ΔTmax ÷ RθJA = 15°C ÷ 147°C/W = 102 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 102 mW ÷ 12 mA = 8.5 V
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤ VCC(est).
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then
reliable operation between VCC(est) and VCC(max) requires
enhanced RθJA. If VCC(est) ≥ VCC(max), then operation between
VCC(est) and VCC(max) is reliable under these conditions.
POWER DERATING
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
12
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Package SM, 3-Pin SIP
For Reference Only – Not for Tooling Use
(Reference DWG-9084-B)
Dimensions in Millimeters – NOT TO SCALE
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
0.90 REF
22
33
11
B
4 X 7°
4 X 10°
A
Branded
Face
2 X 2.40 ±0.10
5.80 REF
5.78±0.10
6.42 REF
2.66 REF
0.60 REF
0.79 REF
7.65±0.10
15.58±0.10
19.24 REF
23.36 REF
1.60 ±0.10
5.00 ±0.10
A
B
C
C
D Branding scale and appearance at supplier discretion
7.00±0.10
E
E
0.30 REF
3 X 1.00 ±0.10
3 X 0.51 ±0.10 0.25 ±0.05
2.00±0.10
2 X 1.27 ±0.10
1.15 ±0.05
E1 E2
2.72
3.12
0.72 REF
3.83 REF
2.2
F
F
F
FF
F
D
7.99 REF
LLLLLLL
NNN[NNNN]
YYWW
1
Standard Branding Reference View
= Supplier emblem
= Lot identifier
= Last three numbers of device part number and optional
subtype codes
= Last two digits of year of manufacture
= Week of manufacture
L
N
Y
W
Dambar removal protrusion (12X)
Gate and tie bar burr area
Active Area Depth 0.40 ±0.05 mm
Molded lead bar for preventing damage to leads during shipment
Hall elements (E1 and E2), not to scale
True Zero-Speed High-Accuracy
Gear Tooth Sensor IC
ATS668LSM
13
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
For the latest version of this document, visit our website:
www.allegromicro.com
Copyright ©2017, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to
permit improvements in the performance, 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’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
Revision History
Number Date Description
– March 17, 2017 Initial release
1 March 22, 2017 Updated Power Derating and Thermal Characteristics
2 April 24, 2017 Updated Electrical Characteristics table
