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LM5141-Q1: Powering Sensing Circuitry from VDDA Output Pin

Ansel Barchowsky
Prodigy 75 points
Part Number: LM5141-Q1
Other Parts Discussed in Thread: TINA-TI, LM5141

I'm in the process of designing a buck converter based on the LM5141-Q1 which has some external sensing needs. Six OP-AMPS will be used to help measure input and output voltage and currents from the converter, each of which will draw a maximum of 2mA on the 5V supply to which they are connected. I was wondering if it would be possible to use the VDDA pin from the internal LDO to supply this minimal power. If not, I can add an external LDO for these OP-AMPS, but space is a serious constraint for this application, so I was hoping to source the current from the internal LDO.

As a separate concern, I was wondering if an unencrypted version of the PSpice model for the LM5141-Q1 was planned for release on spicerack, and if not, would it be possible to request one?

Thank you very much,

Ansel

  • 0
    TI__Prodigy 700 points
    Hi Ansel,

    keep in mind the internal LDO is not always 5Vout. From the datasheet:
    a) "Normally VDDA is 5 V, but there are two operating conditions where it regulates at 3.3 V. The first is in skip cycle mode with VOUT of 3.3 V. The second is when VIN is less than 5 V. Under these conditions both VCC and VDD will drop below 5 V."
    I would recommend to use an dedicated LDO for the OP-Amp circuit to have no interaction between the circuits.

    b) Unencrypted Spice model we have and can be requested under NDA.
    For simulations you can use TINA-TI spice and export spice model from Webench. Here the link www.ti.com/.../slvmay6

    Best Regards,
    Robert L
  • 0 in reply to Robert Loke
    Prodigy 75 points

    Hi Robert,

    a) Thanks for the feedback. We are operating the LM5141 as a 12V in - 5V out converter, with a very stable input. Because of that, can we expect the internal LDO to always be operating in the 5V range? If so, would you still recommend an external LDO to power the sensing circuitry?

    b) Where should I submit a request for the unencrypted model? Unfortunately for some of the other components in our system, TINA-TI does not seem to be a viable option.

    Thank you very much for your help!

    Ansel