Single Element, Tooth Detecting Speed Sensor IC

ATS601

9

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Functional Description

Sensing Technology

The ATS601LSG contains a single-chip Hall effect sensor IC, a

4-pin leadframe and a specially designed permanent magnet. The

Hall IC supports a chopper stabilized Hall element that measures

the magnetic gradient created by the passing of a ferromagnetic

object. The difference in the magnetic field strength created by

teeth and valleys allows the device to generate a digital output

signal that is representative of the target features, independent

of the direction of target rotation or rotational orientation of the

sensor IC.

The ATS601LSG gear tooth sensor device contains a self-cali-

brating Hall effect IC that provides a Hall element, a temperature

compensated amplifier, and offset cancellation circuitry. The

IC also contains a voltage regulator that provides supply noise

rejection over the operating voltage range. The Hall transducers

and the electronics are integrated on the same silicon substrate by

a proprietary BiCMOS process. Changes in temperature do not

greatly affect this device due to the stable amplifier design and

the offset rejection circuitry.

Output Polarity

The polarity of the output is programmable to either be low

opposite target teeth (LT option) or high opposite target teeth (HT

option). See figure 5.

Start-Up Detection

The ATS601LSG always powers-on in the high output state,

independent of the polarity option (HT or LT) selected. The

output will transition to the low state at the first mechanical edge

corresponding to a high-to-low output transition. See figure 6.

Threshold Update

The ATS601 has two programmable options for the threshold

update used to establish running mode switching levels. With

single-tooth update (1 option) the switching threshold for a tooth

Target

Mechanical Profile

Processed

Input Signal, V

PROC

0

V+

Target

Magnetic Profile

|B|

0

Output Switch State

HT option

(Following)

On Off On Off On Off On

Off

Output Switch State

LT option

(Inverting)

On Off On Off On Off On Off

Figure 5. Output Polarity (when connected as shown in figure 1)

Figure 6. Start-up behavior (when connected as shown in figure 1)

Power-on opposite

middle of valley

Rising mechanical

edge

Falling mechanical edge

Target motion

HT option output

LT option output

Power-on opposite

rising mechanical edge

HT option output

LT option output

Power-on opposite

middle of tooth

HT option output

LT option output

Power-on opposite

falling mechanical edge

HT option output

LT option output