Some quadrature encoder datasheets describe their outputs as either Differential Line Driver or Line Driver. On closer inspection of the diagrams, they appear to be the same thing (differential line drivers).

However, my research tells me that a differential line driver provides 0-0.8v when Low, and 2-5v when High (TTL?). I.e. an "active" circuit without floating, and therefore no need for pull up/down resistors.

On the other hand, I found this definition for Line Driver:

"A line driver is a sourcing output. When in the on state, a line driver will supply Vcc. In the off state, a line driver will float. Because of this, a sinking input is required for proper operation. Please refer to the table below for a simple example of a line driver."

This implies a pull up/down resistor is needed.

So, what is the difference/similarity between the two, if any, in regards to quadrature encoders?

  • \$\begingroup\$ It depends on the specific line driver. \$\endgroup\$ – immibis May 3 '18 at 6:27
  • \$\begingroup\$ There is no generic line driver. Find one, link the data sheet and someone will tell you what it does. \$\endgroup\$ – Andy aka May 3 '18 at 7:38
  • \$\begingroup\$ ecatalog.dynapar.com/downloads/60Roto_DS_701841-0002.pdf This is what I'm planning on using. What does it mean by "sink or source"? \$\endgroup\$ – M-R May 3 '18 at 7:39
  • \$\begingroup\$ @Andyaka, encoder.com/core/files/encoder/products/… This is an example of an encoder, whose datasheet uses the term "line driver". Does that mean I am to assume that when the encoder channel is reading "low", the wire is left floating? \$\endgroup\$ – M-R May 3 '18 at 9:06

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