TPS73633 parallel connection

Expert 1200 points

Hi Darwin,

I am sorry to insist but I would like to check on this:

The reazon why I want to use 2 LDOs in parallel configuration it is not to increase the current. It's is a safety issue.

My idea is to connect in parallel two NMOS LDOs TPS73633 with different battery input. If any battery fails, the regulated output should be fine because the other battery input is still working. No current will flow back to the broken battery because the LDOs are NMOS.

Moreover, the load current is 1/2 of the output current of a single LDO, so in case the current is not balanced, the LDO that has to deliver all the current is able to do it.

Do you see any problem in this configuration?

Thanks a lot in advance.

5 Replies

  • Hi Nuba,

    If load sharing of more than the rated current of TPS73633 is not an issue, such as your application, then I do not see a problem with your configuration.

    Regards,

    Darwin 

  • Expert 1200 points

    In reply to Darwin Fernandez:

    Hi Darwin.

    Thanks a lot for the answer.

    Is there any app note about the different kinds of LDOs failure modes: short circuit, open circuit....

    Best Regards.

    Nuba

  • In reply to Nuba:

    Hi Nuba,

    Unfortunately, we do not have application notes for this. Typically, if there is internal protection (current, thermal) that takes the output voltage out of regulation but does damage the part. However, from what I have seen, MOSFETS usually damage into a short circuit.  If the output of the LDO just follows the input without regulating, the LDO is probably damaged.

    Regards,

    Darwin  

  • Expert 1200 points

    In reply to Darwin Fernandez:

    Dear Darwin,

    Thanks for the answer.

    So, if i understood you right, from what you have seen, MOSFETS damage in shortcircuit. So Input and Output are connected together and i will see at the output the input voltage. Is this what you meant?

    Is there any failure mode that  a LDO can present a shortcircuit to GND at the output? This case would be more dangerours to me since i have two LDO in parallel.

    Thanks in advance.

  • In reply to Nuba:

    Hi Nuba,

    Yes, anytime I notice the output following the input all the way to the maximum input rating, the IC is probably damaged.

    Fortunately, the TPS73633 has short circuit protection and limits the output current of the device to 450mA when the output goes below 0.5V. See page 13 of the datasheet.

    Regards,

    Darwin