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ATS675LSE Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer ATS675LSE
Beschreibung Self-Calibrating TPOS Speed Sensor
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 13 Seiten
ATS675LSE Datasheet, Funktion
ATS675LSE
Self-Calibrating TPOS Speed Sensor
Optimized for Automotive Cam Sensing Applications
Features and Benefits
Chopper stabilized; optimized for automotive cam
sensing applications
Optimized absolute timing accuracy step size through
gradual transition from TPOS to Running Mode
High immunity to signal anomalies resulting from
magnetic overshoot and peak-to-peak field variation
Tight timing accuracy over full operating
temperature range
True zero-speed operation
Automatic Gain Control circuitry for air gap
independent switchpoints
Operation at supply voltages down to 3.3 V
Digital output representing target profile
Undervoltage lockout (UVLO)
Patented Hall IC-magnet system
Increased output fall time for improved radiated
emissions performance
Package: 4-pin SIP module (suffix SE)
Not to scale
1
2
34
Description
The ATS675 is the next generation of the Allegro® True
Power-On State (TPOS) sensor family, offering improved
accuracy compared to prior generations, gradual TPOS to
Running Mode adjustment for accuracy-shift reduction,
and longer output fall time for improved radiated emissions
performance. The ATS675 provides absolute zero-speed
performance and TPOS information.
The sensor incorporates a single-element Hall IC with an
optimized custom magnetic circuit that switches in response
to magnetic signals created by a ferromagnetic target. The IC
contains a sophisticated digital circuit designed to eliminate
the detrimental effects of magnet and system offsets. Signal
processing is used to provide device performance at zero target
speed, independent of air gap, and which adapts dynamically
to the typical operating conditions found in automotive
applications, particularly camshaft-sensing applications.
High resolution peak-detecting DACs are used to set the adaptive
switching thresholds of the device, ensuring high accuracy
despite target eccentricity. Internal hysteresis in the thresholds
reduces the negative effects of anomalies in the magnetic signal
(such as magnetic overshoot) associated with targets used in
many automotive applications. The resulting output of the
device is a digital representation of the ferromagnetic target
profile. The ATS675 also includes a low bandwidth filter that
increases the noise immunity and the signal-to-noise ratio of
the sensor.
The device package is lead (Pb) free, with 100% matte tin
leadframe plating.
Typical Application
VS
CBYPASS
0.1 μF
1
VCC
ATS675
32
A TEST
OUT
GND
4
A Recommended
VPU
RPU
Sensor
Output
CL
ATS675LSE-DS
Figure 1. Operational circuit for the ATS675






ATS675LSE Datasheet, Funktion
ATS675LSE
Self-Calibrating TPOS Speed Sensor
Optimized for Automotive Cam Sensing Applications
Signal Processing Characteristics
VOUT(high)
tr
tf
VOUT(low)
Figure 2. Output Rise Time and Output Fall Time
BST
BHYS
BHYS
Switchpoints
100
90
100
90 10
0
VPROC(high)
td tf
10
0 VPROC(low)
Figure 3. Output Delay Time and Output Fall Time
BST
VPROC(high)
VPROC(high)
Operational
Signal
Amplitude
VPROC(reduce)
Signal
Reduction
Breduce(G)(max)
Breduce(NG)(max)
Full Signal
Processing
Reduced
Signal
Processing
Lowest peak
0
Figure 4. Switchpoint and Internal Hysteresis
VPROC(low)
VPROC(low)
(Baseline)
Figure 5. Maximum Allowable Signal Reduction. Breduce for a given tooth
signal is calculated as follows:
Breduce
=
Signal Reduction
Operational Signal Amplitude
100%
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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ATS675LSE pdf, datenblatt
ATS675LSE
Self-Calibrating TPOS Speed Sensor
Optimized for Automotive Cam Sensing Applications
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 appli-
cation. This section presents a procedure for correlating factors
affecting operating TJ. (Thermal data is also available on the
Allegro MicroSystems 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 = 7 mA, and RθJA = 77 °C/W, then:
PD = VCC × ICC = 12 V × 7 mA = 84 mW
ΔT = PD × RθJA = 84 mW × 77 °C/W = 6.5°C
TJ = TA + ΔT = 25°C + 6.5°C = 31.5°C
A worst-case estimate, PD(max), represents the maximum allow-
able power level, 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=101 °C/W, TJ(max) =165°C, VCC(max)=24V, and
ICC(max) = 10 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔT(max) = 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) = ΔT(max) ÷ RθJA = 15°C ÷ 101 °C/W = 148.5 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 148.5 mW ÷ 10 mA = 14.9 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 RθJA. 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
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