AN4013 datasheet(30/37 Pages) STMICROELECTRONICS

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Advanced features for motor control

AN4013

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DocID022500 Rev 4

4.3.4

Specific features for feedback measurement

Encoder modes

The incremental encoder is a type of sensor used in motor-control applications to measure

the angular position.

In general, the incremental encoder generates three signals: phase A, phase B and index.

The direction of the motor depends if Phase A leads Phase B, or Phase B leads Phase A. A

third channel, Index pulse, occurs once per revolution and is used as a reference to

measure an absolute position.

The Phase A and B output signals are connected to the encoder interface to compute the

frequency and then deduce the velocity and the position. Velocity and position information

can be measured at X2 or X4 resolution. The following figures explain the encoder interface

function.

The timer's counter is incremented or decremented for each transition on both inputs TI1

and TI2.

Figure 7. Position at X4 resolution

The timer's counter is incremented or decremented for each transition on the selected input

TI1 or TI2.

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