Single Element, Tooth Detecting Speed Sensor IC

ATS601

10

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615–0036 U.S.A.

1.508.853.5000; www.allegromicro.com

is established based on the measured peak value of the previous

tooth. This option can be used with any number of teeth-targets,

and is comparable to the Continuous Update mode used on many

Allegro sensor ICs.

With the four-tooth update (4 option), peak information from the

last four teeth is stored in on-chip memory. Switching thresholds

for the upcoming tooth are established based on the stored infor-

mation from four teeth earlier. When used with four-tooth targets,

this is allows for optimized switchpoints based on the same tooth

from the previous revolution of the target. The programmable

threshold update results in improved output switching accuracy

on targets with runout and tooth-to-tooth variation (including

narrow valleys). With the four-tooth update option, during the

first target rotation the device behaves the same as in single-

tooth update while one rotation of target information is stored to

memory. Similarly, if a direction change or other sudden mag-

netic signal change is detected, the device returns to single-tooth

update mode and re-learns four target teeth before returning to

four-tooth update mode.

Switchpoints

The running mode switchpoints in the ATS601LSG are estab-

lished dynamically as a percentage of the amplitude of the signal,

with the U or M options. The ATS601LSG uses a single switch-

ing threshold (operate and release point identical) with internal

hysteresis.

performance switching accuracy on both rising and falling edges

while maintaining immunity to false switching on noise, vibra-

tion, backlash, or other transient events. Figure 7 demonstrates

the function of this hysteresis when switching on an anomalous

peak.

Power Supply Protection

The ATS601LSG contains an on-chip regulator and can operate

over a wide range of supply voltage levels. For applications using

an unregulated power supply, transient protection may be added

externally. For applications using a regulated supply line, EMI

and RFI protection may still be required. Contact Allegro for

information on EMC specification compliance.

When the supply voltage falls below the undervoltage lockout

state. The device remains in that state until the voltage level is

netic profile have no effect until voltage is restored. This prevents

false signals caused by undervoltage conditions from propagating

to the output of the sensor IC.

Time

Switchpoint Level

On

Output State

for POL Bit = 0

Off

On

Off

Figure 7. Switching on internal hysteresis