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TPS65023: Looking to add an additional LDO in parallel to the PMIC's LDO

Bob C
Intellectual 615 points
Part Number: TPS65023
Other Parts Discussed in Thread: TPS650250, TLV755P, TLV758P, TLV733P, TPS7A11, LP5912

Hello,

We're using the TPS65023, and we need additional current from one of the LDO rails in certain circumstances (e.g., shields are added).

The TPS65023 states the LDOs have reverse conduction prevention and allow the possibility to connect external regulators in parallel. 

We want to add an additional discrete LDO to provide up to an additional 500 mA of current @ 1.1V.  

Can I please get a recommendation on a low cost part that we can power simultaneously and in parallel with the 65023 LDO output?

We're looking for something small and cheap. (less than 50 cents).  

Hereis a a link to our online hardware spec for this design: mindchasers.com/.../darsena-hw-spec

Thank you,

Bob

  • 0
    TI__Mastermind 30310 points
    Bob,

    The TPS65023 has another limitation for the LDOs that you may not be aware of: Section 7.5.1.1 DEFLDO1 and DEFLDO2 on page 28 of the TPS65023 datasheet explains that the DEFLDO1/2 pins can only be set high or low, resulting in 4 possible combinations of LDO output voltages.

    Your options would be to (a) ignore the TPS65023 LDOs completely and use only external LDOs to generate your 1.1V and 2.5V rails in the spec you shared, or (b) use the TPS650250 which has LDOs which can be configured externally using feedback resistor dividers. The TPS650250 is capable of less output current on the DC-DC converter rails, but it could work depending on the actual load current required by your system (which is not included in the spec you shared).

    Either way, I would recommend the TLV755P fixed output voltage or the TLV758P adjustable output voltage LDO to meet your requirements of 1.1V output at 500-mA load current.
  • 0 in reply to Brian Berner
    Intellectual 615 points

    Hi Brian,

    Thank you for pointing out the DEFLDO pin straps.  However, our board leaves the LDOs disabled until the micro programs them via the I2C bus.  

    BTW, we already have working boards with the TPS65023, but we want to provide an option for more current on the next board spin. 

    The TLV755P with a 1.1V fixed output looks like a great choice.  However, it only appears to be available in the X2SON package.  Can you please confirm this?

    I was just reading about this package in November's PC Design & Fab magazine.  We're trying to keep the PCB cost low, so it doesn't have any plated VIPs or 4 mil traces (6 mil and up).  

    Hopefully you'll tell me it's also available in one of the alternate packages, or we'll figure out a way to fit it into the PCB fabrication process.

    Lastly, can we keep both 1.1V LDO rails enabled to drive up to 700 mA current?   I'm going to dig into the datasheet later today. 

    Thanks again,

    Bob

  • 0 in reply to Bob C
    TI__Mastermind 30310 points
    Bob,

    Yes, I see the TLV75511P is only available in a single package, as the TLV75511PDQNR (X2SON). I would say that you could order samples of the TLV758P to test this device in your system and generate any voltage you need.

    I am not the expert on the LDOs, nor do I know the expected release date of the TLV758P device (currently listed as PREVIEW), so I will need to re-assign this question to a different forum so the LDO experts can finish answering your questions.
  • 0 in reply to Brian Berner
    TI__Expert 4320 points
    Hi Bob

    Depending on your current needs, we may have some other devices that you may also be interested in.
    In terms of fixed voltages we have the LP5912-1.1DRVR which is in a WSON Package. If less current is needed we also have the TLV733P which comes in both the X2SON package and SOT-23 package. Another added benefit is that it can be capacitor-free (meaning the input/output capacitors are optional for operation).

    If you have any additional questions please let us know.

    Regards,
    Wilson
  • 0 in reply to Wilson Fwu
    Intellectual 615 points
    Hi Wilson,

    We could use the 300 mA device if its possible to drive both LDOs in parallel to power the same load? Does TI recommend using it this way?

    If not, what is your recommendation for a 500 mA LDO that can supply 1.1V and offers a package other than the X2SON?

    Thank you,

    Bob
  • 0 in reply to Bob C
    TI__Expert 4320 points
    Hi Bob,

    No we do not recommend load sharing the LDO with the PMIC.
    Currently we only have a few LDOs that can support 1.1V fixed output and up to 500mA. The TLV755P only has this option in the X2SON package. LP5912 has it in a WSON (2x2) package. The only other device I can recommend is the new TPS7A11 which also comes in a WSON (2x2) package but is considered "LILO" which means it is meant to support lower input and lower output. In terms of adjustable outputs, TLV758P would be the best device as Brian had mentioned earlier.

    Regards,
    Wilson
  • 0 in reply to Wilson Fwu
    Intellectual 615 points
    The LP5912 looks like it might be a good choice. If you don't mind, I'm going to dig into the datasheet for a couple days before closing this out / marking the question resolved.

    Thank you,

    Bob