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ATS667LSG True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Features and Benefits
Optimized robustness against magnetic offset variation Small signal lockout for immunity against vibration Tight duty cycle and timing accuracy over full operating temperature range True zero-speed operation Air gap independent switchpoints Large operating air gaps achieved through use of gain adjust and offset adjust circuitry Defined power-on state (POS) Wide operating voltage range Digital output representing target profile Single chip sensing IC for high reliability Small mechanical size Optimized Hall IC magnetic system Fast start-up Undervoltage lockout (UVLO)
Description
The ATS667 is a true zero-speed gear tooth sensor IC consisting of an optimized Hall IC-rare earth pellet configuration in a single overmolded package. The unique IC and package design provides a user-friendly solution for digital gear tooth sensing applications. This small package can be easily assembled and used in conjunction with gears of various shapes and sizes. 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 (reduced vibration sensitivity). 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 the targets used in many automotive applications. The ATS667 is optimized for transmission applications. It is available in a lead (Pb) free 4-pin SIP package with a 100% matte tin plated leadframe.
Package: 4-pin SIP (suffix SG)
Not to scale
Functional Block Diagram
VCC Voltage Regulator
Automatic Gain Control Hall Amp Offset Adjust
Threshold Comparator PDAC VPROC Reference Generator NDAC PThresh Threshold Logic
NThresh
TEST Current Limit GND Output Transistor VOUT
ATS667-DS, Rev. 2
ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Selection Guide
Part Number Packing*
ATS667LSGTN-T 13-in. reel, 800 pieces/reel *Contact Allegro(R) for additional packing options
Absolute Maximum Ratings
Characteristic Supply Voltage Reverse Supply Voltage Reverse Supply Current Reverse Output Voltage Output Sink Current Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Symbol VCC VRCC IRCC VROUT IOUT TA TJ(max) Tstg Range L Notes See Power Derating section Rating 26.5 -18 -50 -0.5 25 -40 to 150 165 -65 to 170 Unit V V mA V mA C C C
Pin-out Diagram Terminal List
Number 1 2
1 2 3 4
Name VCC VOUT TEST GND Supply voltage Device output Tie to GND or float Ground
Function
3 4
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
2
ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
OPERATING CHARACTERISTICS Valid over operating voltage and temperature ranges; unless otherwise noted
Characteristics Electrical Characteristics Supply Voltage2 Undervoltage Lockout (UVLO) Reverse Supply Current Supply Zener Clamp Voltage Supply Zener Current Supply Current Power-On State Characteristics Power-On State Power-On Time3 OUTPUT STAGE Low Output Voltage Output Zener Clamp Voltage Output Current Limit Output Leakage Current Output Rise Time Output Fall Time D-to- A Converter (DAC) Characteristics Allowable User Induced Differential Offset4,5 Calibration Initial Calibration6 Update Method CALI Possible reduced edge detection accuracy, duty cycle not guaranteed Running mode operation, bounded for decreasing AG, unlimited for increasing AG AGOP AGOPMAX TE AGMAX D Repeatability and duty cycle within specification Output switching only (no missing edges) 100 Gpk-pk ideal sinusoidal signal, TA = 150C, SROT = 1000 rpm (f = 1000 Hz) Percentage of most recent AGpk-pk , single instantaneous air gap increase, f < 500 Hz, VPROC(pk-pk) > VLOE after sudden AG change Wobble < 0.5 mm, AGOP < AGOPMAX , direction of target rotation pin 1 to pin 4 - - 1
Continuous
Symbol VCC VCC(UV) IRCC VZ IZ ICC VCC = -18 V
Test Conditions Operating, TJ < TJ(max)
Min. 4.0 - - 26.5 - 4 4 - - - 26.5 25 - - -
Typ.1 - 3.5 - - - 7 7 High - 100 - 45 - 10 0.6
Max. 24 3.95 - 10 - 15 12 12 - 2 250 - 70 10 - 2
Unit V V mA V mA mA mA - ms mV V mA A s s
ICC = 15 mA, TA = 25 C TA = 25C, TJ < TJ(max), continuous, VZ = 26.5 V Output off Output on Connected as in figure 6 SROT < 200 rpm; VCC > VCC(min) IOUT = 10 mA, Output = on IOUT = 3 mA, TA = 25C VOUT = 12 V, TJ < TJ(max) Output = off, VOUT = 24 V RPULLUP = 1 k, CL = 4.7 nF, VPULLUP = 12 V, 10% to 90%, connected as in figure 6 RPULLUP = 1 k, CL = 4.7 nF, VPULLUP = 12 V, 90% to 10%, connected as in figure 6
POS tPO VOUT(SAT) VZOUT IOUT(LIM) IOUT(OFF) tr tf
BDIFFEXT
User induced differential offset
-
60
-
G
6 -
edge -
Operating Characteristics (with Allegro 60-0 Reference Target) Operational Air Gap Range7 Maximum Operational Air Gap Range Relative Repeatability8 Maximum Single Outward Sudden Air Gap Change9 Duty Cycle 0.5 - - - 42 - - 0.12 40 47 2.5 3.1 - - 52 mm mm deg. % %
Continued on the next page...
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
OPERATING CHARACTERISTICS (continued) Valid over operating voltage and temperature ranges; unless otherwise noted
Characteristics Switchpoint Characteristics Operational Speed Bandwidth Operate Point Release Point Running Mode Lockout Enable (LOE) Running Mode Lockout Release (LOR)
1Typical
Symbol SROT f-3dB BOP BRP VLOE(RM) VLOR(RM)
Test Conditions Allegro 60-0 Reference Target Cutoff frequency for low-pass filter % of peak-to-peak VPROC referenced from PDAC to NDAC, AG < AGmax, VOUT high to low % of peak-to-peak VPROC referenced from PDAC to NDAC, AG < AGmax , VOUT low to high VPROC(PK-PK) < VLOE(RM) = output switching disabled VPROC(PK-PK) < VLOR(RM) = output switching enabled
Min. 0 15 - - - -
Typ.1 - 20 70 30 100 220
Max. 12000 - - - - -
Unit rpm kHz % % mV mV
data is at VCC = 12 V and TA = 25C, unless otherwise noted. Performance may vary for individual units, within the specified maximum and minimum limits. 2 Maximum voltage must be adjusted for power dissipation and junction temperature; see Power Derating section. 3 Power-On Time is the time required to complete the internal Automatic Offset Adjust; the DACs are then ready for peak acquisition. 41 G (gauss) = 0.1 mT (millitesla). 5The device compensates for magnetic and installation offsets. Offsets greater than specification in gauss may cause inaccuracies in the output. 6For power-on S ROT 200 rpm, edges are sensed target mechanical edges (see figure Definitions of Terms for Switchpoints). 7Operational Air Gap Range is dependent on the available magnetic field. The available field is target geometry and material dependent and should be independently characterized. The field available from the Allegro 60-0 reference target is given in the reference target parameter section. 8The repeatability specification is based on statistical evaluation of a sample population, evaluated at 1000 Hz. Repeatability is measured at 150C because the lowest signal-to-noise ratio for the VPROC signal occurs at elevated temperatures. Therefore, the worst-case repeatability for the device will also occur at elevated temperatures. 9Single maximum allowable air gap change in outward direction (increase in air gap).
Definitions of Terms for Switchpoints
Sensed Edgea Reverse Tooth Valley
Forward
Differential Magnetic Flux Density, BDIFF (G)
+B BOP(REV)b BOP(FWD)
b
BRP(REV) BRP(FWD)
-B
Differential Processed Signal, VProc (V)
+V VPROC(BOP) VPROC(BRP) BOP % -V t BRP %
100 %
aSensed Edge: leading (rising) mechanical edge in forward rotation, trailing (falling) mechanical edge in reverse rotation bB
OP(FWD)
triggers the output transition during forward rotation, and BOP(REV) triggers the output transition during reverse rotation
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Reference Target 60-0 (60 Tooth Target) Characteristics
Outside Diameter Face Width Angular Tooth Thickness Angular Valley Thickness Tooth Whole Depth Material
Symbol
Do F t tv ht
Test Conditions
Outside diameter of target Breadth of tooth, with respect to branded face Length of tooth, with respect to branded face Length of valley, with respect to branded face
Typ.
120 6 3 3 3
Units
mm mm deg. deg. mm -
Symbol Key
t Do F ht
tv
Air Gap Branded Face of Package
Low Carbon Steel
-
Reference Gear Magnetic Gradient Amplitude With Reference to Air Gap
1400
Peak-to-Peak Differential Magnetic Flux Density, BDIFF (G)
1200
1000
800
600
400
200
Branded Face of Package
0 0.5
1.0
1.5
2.0
2.5
3.0
Air Gap (mm)
Reference Target 60-0
Reference Gear Magnetic Profile Two Tooth-to-Valley Transitions
500 400 300 200 100 0 -100 -200
Air Gap
(mm) 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.10
Differential B* (G)
3.10 mm AG
-300
0.50 mm AG
-400 -500 0 2 4 6 8 10 12
Gear Rotation ()
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Characteristic Performance
Supply Current (Off) versus Ambient Temperature
14 12 10 VCC (V) 8 6 4 2 0 -50 0 50 TA (C) 100 150 4 12 24 14 12 10 TA (C) -40 25 150
Supply Current (Off) versus Supply Voltage
ICCOFF (mA)
ICCOFF (mA)
8 6 4 2 0 0 10 VCC (V) 20 30
Supply Current (On) versus Ambient Temperature
14 12 10 14 12 10 VCC (V) 4 12 24
Supply Current (On) versus Supply Voltage
ICCON (mA)
ICCON (mA)
8 6 4 2 0 -50 0 50 TA (C) 100 150
8 6 4 2 0 0 10 VCC (V) 20 30
TA (C) -40 25 150
Output Voltage versus Ambient Temperature
180 160 140
Duty Cycle versus Air Gap
Allegro 60-0 Reference Target
52 51 50 49 48 47 46 45 44 43 42 TA (C) -40 25 150
VCC = 12 V, ILOAD = 10 mA
VOUT(SAT) (mV)
120 100 80 60 40 20 0 -50 0 50 TA (C) 100 150
D (%)
0
0.5
1.0
1.5 AG (mm)
2.0
2.5
3.0
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Package Thermal Resistance Symbol RJA Test Conditions* Single-sided PCB with copper limited to solder pads Two-sided PCB with copper limited to solder pads and 3.57 (23.03 cm2) of copper area each side, connected to GND pin in.2 Value 126 84 Units C/W C/W
*Additional information is available on the Allegro website.
Power Derating Curve
25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 20 40 60
VCC(max)
Maximum Allowable VCC (V)
(R
JA
= 84 C/W)
(R
JA
= 126 C/W)
VCC(min)
80 100 120 140 160 180
Temperature (C)
Power Dissipation versus Ambient Temperature
1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 20 40
Power Dissipation, PD (m W)
(R
JA
(R
=
84
JA
=1
C
26
/W
C
)
/W
)
60
80 100 120 Temperature (C)
140
160
180
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Functional Description
Hall Technology The ATS667 contains a single-chip differential Hall-effect sensor IC, a samarium cobalt pellet, 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, VPROC, that is processed for 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 compensation circuitry. The Hall transducers and signal processing 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 3 presents the automatic translation of the mechanical profile, through the magnetic profile that it induces, to the digital output signal of the ATS667. 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 IC Output Signal, displays the square waveform corresponding to the digital output signal that results from a rotating gear configured as shown in figure 2, and electrically connected as in figure 6. That direction of rotation (of the gear side adjacent to the package face) 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 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 polarity 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 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 nearest to the package.
Mechanical Position (Target movement pin 1 to pin 4)
This tooth sensed earlier
Target (Gear)
This tooth sensed later
Target Magnetic Profile
+B
Target (Gear) Element Pitch Hall Element 2 South Pole North Pole (Pin 4 Side) Hall Element 1 Hall IC Pole Piece (Concentrator) Back-biasing Rare-earth Pellet Case (Pin 1 Side)
Package Orientation to Target
Branded Face Hall Element Pitch
IC
Sensor Branded Face Pellet
Dual-Element Hall Effect Device
Back-Biasing
Pin 4 Side
(Package Top View)
Pin 1 Side
IC Internal Differential Analog Signal, VPROC
Figure 1. Relative motion of the target is detected by the dual Hall elements mounted on the Hall IC.
BOP(#1) BRP(#1)
BOP(#2) BRP(#2)
IC Internal Switch State
Rotating Target Branded Face of Package
On IC Output Signal, VOUT
Off
On
Off
1
4
Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation results in a high output state when a tooth of the target gear is nearest the package face (see figure 3). A right-to-left (pin 4 to pin 1) rotation inverts the output signal polarity.
Figure 3. The magnetic profile reflects the geometry of the target, allowing the ATS667 to present an accurate digital output response.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Continuous Update of Switchpoints Switchpoints are the threshold levels of the differential internal analog signal, VPROC , at which the device changes output signal state. The value of VPROC is directly proportional to the magnetic flux density, B, induced by the target and sensed by the Hall elements. As VPROC rises through a certain limit, referred to as the operate point, BOP , the output state changes from high to low. As VPROC falls below BOP to a certain limit, the release point, BRP , the output state changes from low to high.
(A) TEAG varying; cases such as eccentric mount, out-of-round region, normal operation position shift
As shown in panel C of figure 4, threshold levels for the ATS667 switchpoints are established as a function of the peak input signal levels. The ATS667 incorporates an algorithm that continuously monitors the input signal and updates the switching thresholds accordingly with limited inward movement of VPROC. The switchpoint for each edge is determined by the detection of the previous two signal edges. In this manner, variations are tracked in real time.
(B) Internal analog signal, VPROC, typically resulting in the IC
V+
Smaller TEAG
Larger TEAG
Smaller TEAG
Target
Target
VPROC (V)
IC
Smaller TEAG
IC
Larger TEAG 0
Hysteresis Band (Delimited by switchpoints) Target Rotation () 360
(C) Referencing the internal analog signal, VPROC, to continuously update device response
BOP(#1) BOP(#2) BOP(#3) Pk(#7) Pk(#5) BOP(#4) Pk(#9) Pk(#3)
BHYS 1 2 3 4
Switchpoint BOP(#1) BRP(#1) BOP(#2) BRP(#2) BOP(#3) BRP(#3) BOP(#4) BRP(#4)
Determinant Peak Values Pk(#1), Pk(#2) Pk(#2), Pk(#3) Pk(#3), Pk(#4) Pk(#4), Pk(#5) Pk(#5), Pk(#6) Pk(#6), Pk(#7) Pk(#7), Pk(#8) Pk(#8), Pk(#9)
V+
Pk(#1)
VPROC (V)
VPROC(BOP)(#1) BHYS(#1)
VPROC(BOP)(#2) BHYS(#2)
BHYS(#3) VPROC(BOP)(#3)
VPROC(BOP)(#4) BHYS(#4) VPROC(BRP)(#4)
VPROC(BRP)(#1) Pk(#4) Pk(#2) BRP(#1)
VPROC(BRP)(#2) Pk(#6)
VPROC(BRP)(#3)
Pk(#8) BRP(#2) BRP(#3) BRP(#4)
Figure 4. The Continuous Update algorithm allows the Allegro IC to interpret and adapt to variances in the magnetic field generated by the target as a result of eccentric mounting of the target, out-of-round target shape, and similar dynamic application problems that affect the TEAG (Total Effective Air Gap). Not detailed in the figure are the boundaries for peak capture DAC movement which intentionally limit the amount of inward signal variation the IC is able to react to over a single transition. The algorithm is used to establish and subsequently update the device switchpoints (BOP and BRP). The hysteresis, BHYS(#x) , at each target feature configuration results from this recalibration, ensuring that it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, VPROC. As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the IC as a varying magnetic field, which results in proportional changes in the internal analog signal, VPROC, shown in panel B. The Continuous Update algorithm is used to establish switchpoints based on the fluctuation of VPROC, as shown in panel C.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
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 IC on such spurious signals. Calibration can be performed using the actual target features.
Target, Gear
A typical scenario is shown in figure 5. The Start Mode Hysteresis, POHYS , is a minimum level of the peak-to-peak amplitude of the internal analog electrical signal, VPROC, that must be exceeded before the ATS667 starts to compute switchpoints.
Target Magnetic Profile
Differential Signal, VPROC Start Mode Hysteresis, POHYS
BOP(initial) BRP BOP
2 3 4
BRP(initial)
BOP
IC Position Relative to Target If exceed POHYS on high side If exceed POHYS on low side
1
Output Signal, VOUT
Figure 5. Operation of Start Mode Hysteresis * At power-on (position 1), the ATS667 begins sampling VPROC. * At the point where the Start Mode Hysteresis, POHYS , is exceeded, the device establishes an initial switching threshold, by using the Continuous Update algorithm. If VPROC is falling through the limit on the low side (position 2), the switchpoint is BRP , and if VPROC is rising through the limit on the high side (position 4), it is BOP . After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid VPROC value exceeding the Start Mode Hysteresis can be generated either by a legitimate target feature or by excessive vibration. * In either case, because the switchpoint is immediately passed as soon as it it established, the ATS667 enables switching: --If on the low side, at BRP (position 2) the output would switch from low to high. However, because output is already high, no output switching occurs. At the next switchpoint, where BOP is passed (position 3), the output switches from high to low. --If on the high side, at BOP (position 4) the output switches from high to low. As this example demonstrates, initial output switching occurs with the same polarity, regardless of whether the Start Mode Hysteresis is exceeded on the high side or on the low side.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
10
ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Undervoltage Lockout When the supply voltage falls below the undervoltage lockout voltage, VCC(UV) , the device enters Reset, where the output state returns to the Power-On State (POS) until sufficient VCC is supplied. ICC levels may not meet datasheet limits when VCC < VCC(min). This lockout feature prevents false signals, caused by undervoltage 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. For devices that must 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 for information on the circuitry needed for compliance with various EMC specifications. Refer to figure 6 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 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 7 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 continuously 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 variations over time. Running Mode Lockout The ATS667 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. Assembly Description The ATS667 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
VCC ATS667 1 CBYPASS 0.1 F (Required) VCC VOUT 2
VPULLUP
V+
RPULLUP
Internal Differential Analog Signal Response, without AGC
AGLarge
AGSmall
GND 4
TEST 3
CL
V+ Internal Differential Analog Signal Response, with AGC AGSmall AGLarge
Figure 6. Typical circuit for proper device operation.
Figure 7. 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, as shown in the lowest panel.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Power Derating
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 application. This section presents a procedure for correlating factors affecting operating TJ. (Thermal data is also available on the Allegro website.) The Package Thermal Resistance, RJA, is a figure of merit summarizing 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, RJC, is relatively small component of RJA. 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 x IIN T = PD x RJA TJ = TA + T For example, given common conditions such as: TA= 25C, VCC = 12 V, ICC = 7.5 mA, and RJA = 126 C/W, then: PD = VCC x ICC = 12 V x 7.5 mA = 90 mW T = PD x RJA = 90 mW x 140 C/W = 11.3C TJ = TA + T = 25C + 11.3C = 36.3C A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max), at a selected RJA and TA. (1) (2) (3) Example: Reliability for VCC at TA = 150C, package SG, using a single-layer PCB. Observe the worst-case ratings for the device, specifically: RJA = 126 C/W, TJ(max) = 165C, VCC(max) = 24 V, and ICC(max) = 12 mA. Calculate the maximum allowable power level, PD(max). First, invert equation 3: Tmax = 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) = Tmax / RJA = 15C / 126 C/W = 119 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) / ICC(max) = 119 mW / 12 mA = 9.9 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 RJA. If VCC(est) VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
12
ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Package SG, 4-Pin SIP
F
5.500.05
E B
2.20
8.000.05 LLLLLLL NNN 5.800.05
E1 E2
Branded Face
YYWW
1.700.10 4.700.10 1 2 3 4 A 0.600.10 0.710.05
D
Standard Branding Reference View = Supplier emblem L = Lot identifier N = Last three numbers of device part number Y = Last two digits of year of manufacture W = Week of manufacture
For Reference Only, not for tooling use (reference DWG-9002) Dimensions in millimeters A Dambar removal protrusion (16X) +0.06 0.38 -0.04 24.650.10 0.400.10
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides) C Thermoplastic Molded Lead Bar for alignment during shipment D Branding scale and appearance at supplier discretion E F
Active Area Depth, 0.43 mm Hall elements (E1, E2), not to scale
15.300.10
A
1.0 REF 1.600.10
C
1.270.10 5.500.10
0.710.10
0.710.10
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
13
ATS667LSG
True Zero-Speed, High Accuracy Gear Tooth Sensor IC
Copyright (c)2009, Allegro MicroSystems, Inc. The products described herein are manufactured under one or more of the following U.S. patents: 5,264,783; 5,389,889; 5,442,283; 5,517,112; 5,581,179; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; 6,091,239; 6,100,680; 6,232,768; 6,242,908; 6,265,865; 6,297,627; 6,525,531; 6,690,155; 6,693,419; 6,919,720; 7,046,000; 7,053,674; 7,138,793; 7,199,579; 7,253,614; 7,365,530; 7,368,904; or other patents pending. 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 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 life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website: www.allegromicro.com
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
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