SNOAA58 October 2020 DS26F31MQML-SP , DS26F32MQML-SP , SN55LVDS31-SP , SN55LVDS33-SP
The circuit biases the negative input of each receiver channel slightly above ground. Positive feedback changes the bias point of the positive input depending on the output state of the receiver. When the output is high, the positive input is biased higher than the negative input; when the output is low, the positive input is biased lower than the negative input. In this way, the receiver always remains in the last state that it was actively driven to. The time constant of the AC-coupling circuit is irrelevant, and there is no minimum operating frequency.
| Differential Inputs | Enables | Outputs | |
|---|---|---|---|
| VID = V(A) – V(B) | G | G | Y |
| VID ≥ 50 mV | H | X | H |
| X | L | H | |
| VID ≤ –50 mV | H | X | L |
| X | L | L | |
| X | L | H | Z |
Isolation is provided by the AC-coupling capacitors. These should be chosen with a voltage rating greater than the isolation voltage required. For improved failure tolerance, two capacitors in series can be used; however, each capacitor must be rated for the full isolation voltage.