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LMR36506: RRPER Vref specs

Erik Floden
Prodigy 30 points
Part Number: LMR36506


I have been working on the adjustable output LMR36506 trying to get 3V output, but I keep finding that the resistor feedback calculation doesn't match within what is expected. Using 1M ohm between the output and FB and 500k between FB and GND - getting roughly 3.18V.

Vref looks to be 1.04V when probing FB with a DMM, and the only mention of Vref in the datasheet is referring to the FPWM - what is the spec of the reference?

Thanks in advance.

  • 0
    TI__Mastermind 22300 points

    Hello,

    The device regulates to a voltage reference of 1V (see Section 7.5 of datasheet). The voltage that you are measuring on the FB pin is not the reference voltage of the device, it is the feedback voltage created by your voltage divider, which is then compared to the reference. (See block diagram in Section 8.2)

    Your top feedback resistance is quite large. Typically, it is recommended to use RFBT in a range of 100k to 1M. You should lower the RFBT value from the maximum of 1M.

    What are your operating conditions aside from Vout? (Vin, Fsw, AUTO/FPWM, Iout, etc.)

    Best regards,

    Ridge

  • 0 in reply to Ridge Lahti
    TI__Mastermind 22300 points

    Hello,

    Since we have not heard from you in a while, I am going to close this thread. If you have more questions, you can re-open this thread by replying or create a new thread.

    Best regards,

    Ridge