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???
04/04/12 11:09
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 		 #187002 - It's a high speed circuit !!!!
Responding to: ???'s previous message
Although your throughput may be low, this is still a high speed circuit. USB runs at 12MHz and the FT232RL generates an internal 48MHz clock to sample the USB data. You need to make a PCB that's suitable for such a high speed circuit. My advice is:

1. The PCB MUST be double sided so that you can put a ground plane under the FT232.

2. The decoupling capacitors are much too far away from the FT232 chip. They should be surface mount 0603 parts that can be placed close to the chip.

3. Remove the capacitors on the DM and DP lines or at least change them to 0603 SMT parts.

4. Add the TVS to DM, DP and USB 5V as previously mentioned.

5. Connect the shield to ground. Do not leave it floating!

List of 36 messages in thread
TopicAuthorDate
FTDI F232RL Noise issues            01/01/70 00:00      
   GND,cables            01/01/70 00:00      
      of this is it, then            01/01/70 00:00      
   leakage effects..            01/01/70 00:00      
      Thanks for the comments..            01/01/70 00:00      
         changing the serial port data....            01/01/70 00:00      
         cable, bought off the shelf            01/01/70 00:00      
            Test standard solutions            01/01/70 00:00      
               Options..            01/01/70 00:00      
                  VCP /D2X            01/01/70 00:00      
                     Problem exists with both drivers            01/01/70 00:00      
                  Aten serial to USB cable uses a FTDI chip            01/01/70 00:00      
   FTDI chip ESD sensitivity            01/01/70 00:00      
      Thanks Oliver...            01/01/70 00:00      
         Zeners are slow            01/01/70 00:00      
         show Your circuit            01/01/70 00:00      
            F232 is USB powered but.. + circuit            01/01/70 00:00      
         USB Isolator Chips            01/01/70 00:00      
            Isolators            01/01/70 00:00      
         Better than zeners            01/01/70 00:00      
            just a thought            01/01/70 00:00      
               Layout            01/01/70 00:00      
                  VCP/Direct drivers            01/01/70 00:00      
                  Layout attached            01/01/70 00:00      
                     It's a high speed circuit !!!!            01/01/70 00:00      
                        Totally 100% Agreed            01/01/70 00:00      
                           the trouble with schematics ....            01/01/70 00:00      
                              Bandwidth limitation            01/01/70 00:00      
   22 ohms between serial port ground and FT232 ground helps...            01/01/70 00:00      
      of course it does            01/01/70 00:00      
         Erik,            01/01/70 00:00      
            Links please            01/01/70 00:00      
               Link...            01/01/70 00:00      
                  Solved            01/01/70 00:00      
                     Magnetics            01/01/70 00:00      
                        Ethernet input is connected to serial port ground            01/01/70 00:00      

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