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Maybe my best option is to just use the 1 MOSFET for switching the USB VCC and 2 Diodes for power source selection, as long as I can find a diode with a voltage drop of less than 0.25V @ 250mA.
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Thanks, I finally get it :D.
So do you think I should scrap them 2 MOSFETS and should just use 2 diodes like that in the second diagram?
I have tried Schottky diodes (SS12 E3 **broken link removed** to be exact) in my circuit, the voltage drop I get is around 0.3V - 0.4V, I also tried 1N5817...
Thanks,
So the second diagram with the diodes is ok, but the first diagram with MOSFETS in place of diodes is not ok?
I found this on the internet showing MOSFETS being used in place of diodes, does this look correct?
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Thanks, just trying to understand why this wouldn't work, the above diagram and the one in this post should be equivalent except one uses MOSFETS to do the job of the two diodes right?
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I rebuilt the circuit and it worked fine (so, I must have just had something the wrong way around) with only around 30mV voltage drop (does that sound about right?).
I modified the cct diagram out of the FT232R data sheet and added in back to back MOSFETS.
I am trying to have two MOSFETS act...
I have made a circuit based on the FT232R data sheet example "Figure 6.3 Bus Powered with Power Switching Configuration". Basicly it uses a IRLML6402 (P-Channel MOSFET) tp power up the rest of the circuit once the FT232R has request > 100mA current.
The voltage drop over the IRLML6402 is 0.5V...
Thanks for the very informative replies :D
I should mention, when the project is unplugged from mains it switches over to being USB powered. (I am using 2 diodes for the power supply selection)
Could I still opto-isolate the FT232R and still have it power the board when mains not turned on...
Thanks everyone for all the help with this.
Good news, problem solved, so to help anyone with the same problem, you could try what ended up fixing it for me. Placing a 100k pull down on the 12MHz output solved the problem. I am using the 12Mhz clock out of the FT232R for the UART clock, when...
I have built a project the uses the FT232R USB to serial converter. My project is mains powered and is working fine but I keep worrying that if I plug my project into different computers and laptops that the ground between my project and the PC could be at a different level.
Is this possible...
Thanks guys, that does make sense.
Another issue I have noticed is that when I plug or unplug the USB cable to my project I recieve some random serial data. Is this normal or expected?
My project is in "self powered configuration", so it'a already powered on before I connect or disconnect the...
I am using a FT232R to download files into a project I have built using a terminal program (RealTerm). The Files download fine with no data lose or any other problems even at high Baud rates.
However, the speed of the transfer is incredibly slow. The file I am downloading is 160kB, at a Baud...
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