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Farshid Jafari Harandi
05/31/05 12:16
Read: 734 times

#94159 - many of my questions are answered ! :)
Responding to: Kai Klaas's previous message
Do always use ground wires between signal wires, whenever digital signals are transmitted.
By the way, '51 micros are not designed to directly drive cables or longer copper traces. Due to the special bidirectional port configuration, they do not show low output impedances all the time, which is extremely necessary when directly driving longer connections at port outputs. You should use 74HCMOS ships to drive the signals to the peripheral board, with filters at their according outputs (common mode ferrite choke preferred).

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) ?

Ground wires must always be connected to ground at BOTH ends. Otherwise they do not really work as a shield.

the purpose of don't connecting the ground wires in both ends was that i remembered a discussion here about that and what i remembered from that discussion was telling me to do that , now i know that i was wrong !

By the way, there are also special ferrite chokes for flat cables, where you only need to feed through the cable, without any turns.

I'll check the availability of such a ferrites here,thanks for the tip.i was thinking that there is a need to turn the wire around the core!

You worry too much about inductivity of EMI filters.

You're right it's because i don't have enough info to judge in anything in this field , but now with your help i've got the info :)

I just meant to use this filter directly at input of 5V regulator. That's the proper place for this kind of filter, because DC voltage drops caused by the filter will have the least relevant effects here

i did used the 220uH Toroidal inductor in the main board input with not much luck ,and i'have affected by some voltagte drops, i've to use these EMI filters which i bought today NEAR the LM7805K 5V Regulator .

Dear Kai ,
thanks for your help.
everytime i read your replys i learn much more and many of the questions in my mind are answered ,this makes me feel really satisfied ,i am really appreciated from you.

Best Regards :
Farshid J.H.

List of 22 messages in thread
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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