TMC424 Datasheet – (V1.04 / 2015-JUL-01)

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Copyright © 2011 TRINAMIC Motion Control GmbH & Co. KG

6 Incremental Encoder

Incremental Encoders are translating the rotary motion of a shaft into a two-channel digital quadrature

output. The light emitted from a LED is focused onto a reflective code wheel. As the shaft moves, the

code wheel rotates, reflecting light from an alternating bright and dark pattern.

The TMC424 samples the incoming signals ENCx_A and ENCx_B from the incremental encoder. A

internal algorithm block counts the amount of edges generated by the encoder. A prescaler value can

be used to adapt the incremental encoder resolution to the stepper motor resolution.

For high resolution the TMC424 evaluates the encoder signals 4-times during each encoder step. This

has to be kept in mind when choosing the prescaler value.

Channel A

Channel B

Evaluation

Step

Channel N

Figure 10: Encoder Output and Evaluation

Note: It is possible that the encoder signals ENCx_A, ENCx_B and ENCx_N are polluted with crosstalk

noise. Crosstalk could influence the internal logic, to overcome this problem internal filters are applied

to ensure correct functionality. Furthermore is saves the need for external analog filters.

e.g.: Figure 11: Crosstalk on Encoder Wire shows crosstalk from channel A to channel B.

Figure 11: Crosstalk on Encoder Wire