115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

ATS612LSB

DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,

DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR

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DEVICE DESCRIPTION — Continued

Peak-Detecting vs. AC-Coupled Filters. High-pass

filtering (normal ac coupling) is a commonly used tech-

nique for eliminating circuit offsets. AC coupling has errors

at power on because the filter circuit needs to hold the

circuit zero value even though the circuit may power on

over a large signal. Such filter techniques can only

perform properly after the filter has been allowed to settle,

which is typically greater than one second. Also,

high-pass filter solutions cannot easily track rapidly

changing baselines such as those caused by eccentrici-

ties. Peak detection switches on the change in slope of

the signal and is baseline independent at power up and

during running.

Peak Detecting vs. Zero-Crossing Reference. The

usual differential zero-crossing sensors are susceptible to

false switching due to off-center and tilted installations,

which result in a shift in baseline that changes with air gap.

The track-and-hold peak-detection technique ignores

baseline shifts versus air gaps and provides increased

immunity to false switching. In addition, using

track-and-hold peak-detecting techniques, increased air

gap capabilities can be expected because a peak detector

utilizes the entire peak-to-peak signal range as compared

to zero-crossing detectors that switch on one-half the

peak-to-peak signal.

NOTE — “Baseline” refers to the zero-gauss differential

where each Hall-effect element is subject to the same

magnetic field strength.

Power-On Operation. The device will power on in the

OFF state (output high) irrespective of the magnetic field

condition. The power-up time of the circuit is no greater

than 500

µs. The circuit is then ready to accurately detect

the first target edge that results in a HIGH-to-LOW transi-

tion.

Under-Voltage Lockout. When the supply voltage is

device is OFF and stays OFF irrespective of the state of

the magnetic field. This prevents false signals, which may

be caused by under-voltage conditions (especially during

turn on), from appearing at the output.

Output. The device output is an open-collector stage

capable of sinking up to 20mA. An external pull-up

(resistor) to a supply voltage of not more than 24V must

be supplied.