ATS674 Allegro MicroSystems, ATS674 Datasheet - Page 13

• Manufacturer Part Number: ATS674
• Description: (ATS673 / ATS674) Self-Calibrating TPOS Gear Tooth Sensor Optimized
• Manufacturer: Allegro MicroSystems

ATS673 and
ATS674
Update
The ATS673 and ATS674 incorporate an algorithm that continu-
ously monitors the system and updates the switching thresholds
accordingly. The switchpoint for each transition is determined
by the previous two transitions. Because variations are tracked
Figure 9. 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 (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
Switchpoint
B
B
B
B
B
B
B
B
OP1
OP2
OP3
OP4
RP1
RP2
RP3
RP4
(A) TEAG varying; cases such as
eccentric mount, out-of-round region,
normal operation position shift
Sensor
Target
Determinant
Peak Values
Smaller
TEAG
Pk
Pk
Pk
Pk
Pk
Pk
Pk
Pk
(C) Referencing the internal analog signal, V
1
2
3
4
5
6
7
8
OP
, Pk
, Pk
, Pk
, Pk
, Pk
, Pk
, Pk
, Pk
and B
Self-Calibrating TPOS Gear Tooth Sensor Optimized
2
3
4
5
6
7
8
9
PROC
RP
). The hysteresis, B
, as shown in panel C.
Sensor
Target
V+
PROC
for Automotive Cam Sensing Applications
Larger
TEAG
HYS(#x)
, shown in panel B. The Continuous Update algorithm is used to establish accurate
, at each target feature configuration results from this recalibration, ensuring that
Pk
1
V+
PROC
Pk
in real time, the sensor has high immunity to target run-out and
retains excellent accuracy and functionality in the presence of
both run-out and transient mechanical events. Figure 9 shows
how the devices use historical data to provide the switching
thresholds for a given edge.
B
0
OP1
2
, to continuously update device response
Smaller
TEAG
Pk
B
HYS
B
3
RP1
Pk
B
(B) Internal analog signal, V
typically resulting in the sensor
B
HYS
4
OP2
Pk
Target Rotation (°)
B
B
5
RP2
HYS
Larger
TEAG
(Delimited by switchpoints)
B
Pk
B
HYS
PROC
OP3
6
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
Hysteresis Band
B
.
Pk
HYS
B
7
RP3
B
Pk
B
HYS
PROC
OP4
8
Smaller
Pk
,
TEAG
B
B
9
HYS
RP4
B
360
HYS
t+
13