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11 years, 3 months ago.
The LPC1768 got powered off once connected to the circuit
Hi,
Below is the schematic of my circuit. Only 7 pins are used in this design. I checked all the pins and found out that as long as the pin 1 and 39 were connected to circuit, the microcontroller will be off immediately. (I use the USB cable to provide power for the whole circuit.)
I posted this problem to see if you guys have any ideas about what is going on.
THX
2 Answers
11 years, 3 months ago.
Pin 1 and 39 are the power supply of the USB. If the microcontroller turns off when you connect them (to what?), it is almost certainly a case of a short in the power supply of the circuit you are connecting to it (or it just draws way too much power for a USB port).
Dear Erik,
Thank you for you reply! Just for clarification, the microcontroller is actually only a part of my circuit. I plug the controller into the PCB that I made. I used the USB cable connected to my laptop to power up the whole system. So, what you mean is that it could be a short on my PCB? I upload my PCB just FYI. I checked the socket on the PCB where Pin 1 and 39 are supposed to be plugged in, there is no short between them. Looking forward for your reply. Thank you so much!
posted by 25 Jan 2013There most likely is a short between them. Did you check with a multimeter what the resistance is between p1 and p39 (without mbed plugged in)?
If that is high enough it could still be other things, such as a diode in forward. If you have a bench power supply you can connect it to your PCB (again without mbed), make sure current is limitted to reasonable values, and you can check if a component becomes hot.
posted by 25 Jan 2013