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    USB filtering confusion

    Hi, thanks for your reply. The two filtering configurations are different. My thinking is that you would need to clean the USB supply by filtering before it goes to the FTDI chip. Whereas the top schematic has VBUS1 connected straight to the FTDI chip, surely that means you will have a noisy...
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    USB filtering confusion

    Hi, I have attached a part of the datasheet for a FTDi device. The evaluation schematic board has a filter and 10nF connected between VBUS1 and 0V. I can't see the point of the filter as VBUS1 is connected directly to the FTDI chip (pin 12)? The FTDI hardware recommendations state there is a...
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    USB connector shield

    Hi all, I wonder if someone could please clear this up for me. I have a portable tablet device which has a USB type A connector. Which I am going to connect a separate set of electronics, to get power and GND via a micro USB connector. Do I need to connect the shield of the micro USB to OV or...
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    USB upstream downstream

    Thanks, I was looking for a chip that contained the EMI and series termination resistors too, to save PCB space. Guess I will have to add these and go for a similar ESD chip you mentioned. Could I just not use a duplication of my original schematic i.e. RCLAMP0503F plus EMI cap/ resistor and...
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    USB upstream downstream

    Hi, I have attached a datasheet of a ESD/EMI protection IC. This mentions upstream? I have seen others that mention downstream? This is what is confusing me. Thanks in advance.
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    USB upstream downstream

    Thanks for your help. I was looking at ESD/EMI protection for the additional circuit (all in one package to save PCB space). This is why I posted my earlier message, they give you either a downstream or upstream ESD/EMI protection. Based on my requirements, I believe that I need upstream...
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    USB upstream downstream

    Hi I have attached a schematic. The top schematic is a Stan alone unit that is sometimes connected to a PC. I need to use this to power a circuit to be powered from 3V via the Type A USB. My questions are as follows: 1. The additional circuit has a micro usb 5 pin connector, do I still need...
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    USB upstream downstream

    I will post up a schematic later today, my description is probably not the best. Thanks
  9. R

    USB upstream downstream

    The unit we have connects to a PC for Comms. The same unit when we are not talking to the PC will be connected to our electronics board to provide power. Yes we have a micro usb on our electronics board but for ESD/EMI protection, all I see when looking up suitable protection circuits is that...
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    USB upstream downstream

    We have a unit that is powered from DC or battery. This has USB connections both type A. They connect to a PC. However we are looking to use one of these to power a set of electronics. This electronics will have a micro b connector. It will need USB/EMI protection and then some filtering (of...
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    USB upstream downstream

    Hi, I wonder if someone could please clear this up for me. I have a set of electronics that will be powered from 5V USB. I need some USB ESD/EMI protection. I have seen quite a few solutions but some are upstream and others downstream. I have looked at various sites but am still confused. Which...
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    Car battery voltage spikes

    Thanks for the valuable advice, much appreciated.
  13. R

    Car battery voltage spikes

    Hi, thanks for your advice. I was going to use a X10 probe, perhaps also use a voltage divider to reduce the signal further say using 2 x 1M resistors. I was also going to ring the manufacturer too. Thanks again.
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    Car battery voltage spikes

    I have a OBD unit that has a 60Vmax IC, this is getting destroyed. I am not sure if it is due to voltage transients (due to inductive) or current surge. Hence I am trying to find out by firstly monitoring the voltage, when the car switches on etc. I just want to make sure that I do not destroy...
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    Car battery voltage spikes

    Having some issues that through OBD, which blows up IC. I want to build a voltage comparator to indicate voltage levels initially, hopefully the experiments will help me to see if spikes are the issue.
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    Car battery voltage spikes

    Hi, Thanks for your help. I was going to look at the voltage on the : 1. Car battery - scope across the negative and positive terminals 2. Car cigarette lighter 3. OBD socket through a cable I was slightly concerned that any transients (that I have read about can be >150V) and the last thing...
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    Car battery voltage spikes

    Perhaps I should have said was monitor any spikes when the car is switched on from overnight i.e. starting up the engine
  18. R

    Car battery voltage spikes

    I think starter motor, inductive spikes etc
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    Car battery voltage spikes

    Hi all, I was after a bit of advice. I want to measure voltage spikes from a car battery using my scope. I am building a car voltage monitor (to show state of battery), I am a bit worried that I might damage my scope. Are there any precautions that I should take? Do I need some kind of divider...
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    Testing TVS diode

    Thanks. I will have a look.
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