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UA9638: Output Waveform

Part Number: UA9638

There is a question about UA9638 output waveform. 

We found when output of UA9638 is no connection with downstream circuit, the output waveform is abnormal as A diagram. but when it's connected to downstream circuit, the waveform is ok as B diagram. 

1. Why the output waveform is abnormal without downstream circuit connection?

2. Do you suggest a termination resistor between differential output when the communication distance is only 30 - 50mm?

3. We tried to use 100 Ohm (package: 1206)termination resistance, but it looks the thermal is higher. 

A Diagram

B diagram

  • Hi Brian,

    What are the four waveforms you show, and what is the downstream circuit being connected?

    Typically termination is not required for such short-distance communication.  I think something else is going wrong when the downstream circuit is not connected.  Could you please share a schematic so that we can analyze it further?