Position Sensor IC

with Speed and Direction Output

ATS696PSM

9

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

Pulse Occurrence Location

The output pulse can be programmed to occur at the target

mechanical features of either polarity, i.e., at the center of a tooth

(Option N) or at the center of a valley (Option S) with a ferro-

magnetic target.

Switchpoints

The switchpoints of the ATS696 are established dynamically as a

ure 5. This is accomplished by using two tracking signals to track

are established at fixed percentages of the two tracking signals.

Due to the switchpoint thresholds being established dynamically

as a percentage of the peak-to-peak signal, the effect of a signal

shift is minimized. The position of the output switching threshold

on the speed channel is programmable to ensure the most accu-

rate and consistent output switching. Additionally, it allows the

ATS696 to properly detect direction of rotation when used with

targets containing signature regions. A 50% threshold is recom-

mended for standard crank targets, while the other programmable

options allow for functionality on targets with different mechani-

cal geometries.

Operating Modes

STARTUP HYSTERESIS

When the part is powered on, the first mode of operation is

startup hysteresis mode. While in startup hysteresis, the sensor

IC begins to internally detect the magnetic profile of the target.

This operating mode is used to ensure the detected magnetic

signal amplitude exceeds the minimum gauss threshold for the

ATS696 algorithm to function properly. The required magnetic

signal amplitude is programmable such that it can be optimized

for the application, (see the Programmable Options Table). A

meets the minimum requirements and the part powered on over a

switching feature.

CALIBRATION MODE

Once it is determined that the magnetic signal amplitude meets

the minimum signal requirements, the ATS696 begins its calibra-

tion. The calibration period allows the internal signal tracking

algorithms to properly acquire the magnetic signals.

While in calibration mode, direction information is not available.

given on speed channel switchpoint crossings, independent of the

true target rotation direction. This pulse width is programmable

to meet specific application requirements (see Programmable

Options table).

RUNNING MODE

After calibration is complete, the target relative rotation direc-

tion information is available. This information is communicated

through the variable pulse-width protocol. While forward rotation

grammed for application-specific performance optimization (see

Programmable Options table). Additionally, see the Direction

Detection section for a description of the target’s relative direc-

tion of rotation.

In running mode, signal tracking algorithms are employed,

allowing the ATS696 to track signal drift resulting from tempera-

ture changes, as well as the tracking of target variations such as

pole-to-pole variation and runout, while still maintaining high

accuracy output switching.

The ATS696 provides a tolerance to vibration during calibration.

If the part satisfies the calibration criteria on target vibration,

the part will recover once normal rotation begins. The vibration

recovery algorithm allows the part to recover within three periods

(tooth-valley pairs). The quantity of consecutive monodirectional

pulses that vibration recovery is available for is programmable;

see Programmable Options table. For the standard option of 63,

once the 63rd consecutive pulse in a single direction is given,

vibration recovery can no longer be tripped until the part is reset.

Figure 9: Output Pulse Location

Switching Feature

Switching Feature

Ferromagnetic Target

Ferromagnetic Target

Option S

Option N

Output Pulse Stream

Tooth

Tooth

Valley

Valley

Tooth

Tooth

Valley

Valley