I am designing a 3V battery-powered simple micro-controller to collect sensor data in RAM. How can I avoid a conflict with the 5V of a USB when it comes time to upload the data? Disconnecting the battery would lose the RAM. The solution needs to be very simple as the PCB is very small.

  • $\begingroup$ Are you trying to manage both 5V and 3V supplies such that it will not affect your system. What type of micro controller are using? Please add additional detail. $\endgroup$ Apr 5, 2017 at 12:15
  • $\begingroup$ I am powering a PIC with a 3V battery but then have to attach to 5V USB to get data. $\endgroup$
    – Jim Lewis
    Apr 5, 2017 at 14:22
  • $\begingroup$ What type of PIC? $\endgroup$ Apr 6, 2017 at 13:54

1 Answer 1


There are two possible options based on the limited infomation you have provided

  1. Consider storing data in Non-Volatile Memory.
  2. Use a LDO such as TPS73633 that can support wide input voltage range TPS73633 support a range of 3.5V and 5.5V. The output is 3.3V. An provide both the supply voltage options.

enter image description here

  • $\begingroup$ Non-volatile won't work for me. The LDO does not solve my problem. $\endgroup$
    – Jim Lewis
    Apr 5, 2017 at 14:24
  • $\begingroup$ @JimLewis Why will Non-volatile memory not work. Why does a LDO not solve the problem, $\endgroup$ Apr 5, 2017 at 22:41
  • $\begingroup$ Because I need 16kb and don't want an extra chip. Where is the 3V battery and 5V USB in your LDO circuit? $\endgroup$
    – Jim Lewis
    Apr 6, 2017 at 8:36
  • 1
    $\begingroup$ With a couple of diodes to prevent backflow you can connect both the power sources to the +vbus $\endgroup$ Apr 6, 2017 at 10:23
  • $\begingroup$ Yes that might do the trick though the drop from 3V might be pushing limits. And I suppose I don't need a diode on the higher 5V supply. $\endgroup$
    – Jim Lewis
    Apr 6, 2017 at 10:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.