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REG103UA-3.3 - Can the outputs of two or more of these regulators be tied together?

Robert Chiraz
Prodigy 10 points
Other Parts Discussed in Thread: REG103

REG103UA-3.3 - Can the outputs of  two or more of these regulators be tied together? I am bringing an RS-485 serial interface to a connector as well as the flash programming signals and the +3.3V to the same connector. When I connect multiple circuit boards together the 3.3V regulator outputs from multiple boards are connected. I didn't notice anything in the datasheet about paralleling outputs. In general I know this is not recommended, but I was wondering if the DMOS transistor topology allowed paralleling outputs.

  • 0
    TI__Guru 55940 points
    Hi Robert,

    How much current would the total load be when the circuit boards are all tied together?

    When multiple outputs are tied together, each LDO output will be slightly different. Whichever output is highest will carry the entire load. This is because it will have pulled the outputs of the other LDOs high. When the output of an LDO is biased high, it will let go until the load pulls the output back down (LDOs do not sink current).

    If your output current exceeds 500mA (the rated current for REG103), then you could see issues and run into current limit.

    In general a current sharing design such as the following would be recommended. Unfortunately I am unaware of a design for fixed devices other than using ballast resistors.

    www.ti.com/.../tida-00270

    Very Respectfully,
    Ryan