ATS601LSGTN-LT-WU4-T Datasheet, PDF (11/14 Pages) Allegro MicroSystems – Single Element, Tooth Detecting Speed Sensor IC

ATS601
Single Element, Tooth Detecting Speed Sensor IC
Operating Modes
Startup Hysteresis Mode
After power-on, a minimum amount of peak-to-peak magnetic
movement is required before the ATS601 will begin generating
output edges. This required signal movement threshold is referred
to as the startup hysteresis. There are two programmable options
for this startup hysteresis threshold. With narrow (N option)
startup hysteresis, the device will switch to a farther air gap, but
will have reduced immunity to magnetic overshoot, thus limiting
its close air gap capability. With wide (W option) startup hyster-
esis, the device will have a reduced maximum air gap capability,
but improved magnetic overshoot immunity. After the magnetic
signal exceeds the startup hysteresis value for the first time, the
device will transition to Calibration mode.
Calibration Mode
In Calibration mode, the ATS601 uses threshold based switching
with continuous update. This ensures that all teeth and valleys
are captured correctly, but provides slightly reduced accuracy
relative to Running mode. The device stays in Calibration mode
long enough to correctly capture enough peaks to fill the Running
mode threshold memory. This corresponds to three output edges
with the single-tooth update (1 option) and nine edges with the
four-tooth update (4 option). After Calibration mode is complete,
the device transitions to Running mode.
Running Mode
In Running mode the ATS601 uses threshold based switching
with internal hysteresis described previously, in the Thresh-
old Update and Switchpoints sections. The threshold update is
intended to optimize output switching accuracy when used with
common camshaft targets, including cases with runout and nar-
row target valleys.
Stop Mode
The ATS601 has an internal timer that begins counting on each
output edge. If the timer reaches t_SM before another output edge
occurs, the device moves into Stop mode. Stop mode is the same
as Startup Hysteresis mode, but with a hysteresis value
determined as a percentage of the previously measured target
amplitude. Stop mode ensures no missed or extra output
edges, even during situations with large temperature drifts and
no target rotation.
Watchdog
The ATS601 has a peak detector continuously tracking the mag-
netic signal. If a sudden large signal change causes the sensor IC
output to stop switching but the peak detector continues to detect
valid signal movement, the watchdog will be fired. In case of a
watchdog event, the sensor IC performs a self-reset and returns to
the initial Startup Hysteresis mode to regain output switching.
Allegro MicroSystems, LLC
11
115 Northeast Cutoff
Worcester, Massachusetts 01615–0036 U.S.A.
1.508.853.5000; www.allegromicro.com