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Kai Klaas
06/01/05 08:50
Read: 929 times
Germany


 
#94192 - Long lines
Responding to: Farshid Jafari Harandi's previous message
Farshid said:
Does the MCUs which don't have Bidirectional ports and capable of Sinking/Sourcing 20mA with CMOS outputs can drive long wires (shorter than 50cm) ?

There are some '51 derivatives which can have the ports be programmed as push-pull stages. These will show very low output impedances and are suited to drive longer lines.
Nevertheless, it's the rise time of signal which determines how long the line can be. If the rise time is very short and the lines very long, then you will suffer from transmission line effects. Means, you get trouble with reflections and echoes, unless you use proper termination of the lines. If you need the full bandwidth, then series termination is adequate. But if you don't need the full bandwidth, for instance because you only control some relays or similar, then a simple low pass filter in series to port output can be used. This will help to avoid reflections and to suppress radiation effects. Something in the range of 1...2.2k + 47pF is a good choice.

Kai

List of 22 messages in thread
TopicAuthorDate
Info on Murata Inductors for LC filter ?      Farshid Jafari Harandi      05/27/05 03:55      
   Ground routing and filtering        Kai Klaas      05/27/05 04:57      
      Examples of soft ferrites      Kai Klaas      05/27/05 05:07      
         good link      Farshid Jafari Harandi      05/27/05 17:13      
      Ground routing      Mehdi      05/27/05 07:24      
         Ground routing techniques      Kai Klaas      05/31/05 04:34      
      Ferrite on cables and filtering      Farshid Jafari Harandi      05/27/05 17:05      
         Answers...        Kai Klaas      05/31/05 05:18      
            many of my questions are answered ! :)      Farshid Jafari Harandi      05/31/05 12:16      
               Long lines      Kai Klaas      06/01/05 08:50      
                  the other reason      Erik Malund      06/01/05 09:24      
                     Buffers good !      Farshid Jafari Harandi      06/01/05 17:18      
                  my next PCB would be way much better !      Farshid Jafari Harandi      06/01/05 17:18      
   BL02RN2 in Tehran      Payam Soltany      05/27/05 20:10      
      thanks a thousand dear payam      Farshid Jafari Harandi      05/28/05 09:28      
         On-Board Type EMI Suppression Filters      Payam Soltany      05/28/05 18:37      
         Basics of EMI Filters      Payam Soltany      05/28/05 18:38      
         More...      Payam Soltany      05/28/05 18:40      
         Tell me when it's enough        Payam Soltany      05/28/05 18:43      
            you're doing a favor for me!      Farshid Jafari Harandi      05/28/05 19:49      
               Not all available in Tehran probabely//      Payam Soltany      05/28/05 20:40      
               BL02RN2 Datasheet      Payam Soltany      05/28/05 21:13      

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