• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 306 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5177: CFG pin: "PSM Entry Threshold" vs. "µSleep"

Al Hollmann
Prodigy 40 points
Part Number: LM5177

Tool/software:

Hi dear Experts,

I have three questions:

From the LM5177 datasheet, chp. 7.3.16, i get the information that one can configure the device for a 10% PSM entry level if R_CFG is smaller than ca. 8.3kOhm or a 15% PSM entry level if R_CFG is >= ca. 8.3kOhm.

So far, so good.

Now in the LM5177 eval board user's guide, chp. 2.4.1, it says that µSleep is disabled or enabled corresponding to whether R_CFG is < or >= ca. 8.3kOhm.

This doesn't sound equivalent to the aforementioned datasheet information.

Can you please clarify what "µSleep" means/implies and when (or when not) to activate this feature, or when to use 10% or 15% PSM threshold, respectively?

Also, i'd like to know with which R_CFG setting(s) you performed the eval board measurememts (chp. 4, etc.).

What is the eval board default setting for R_CFG?

And off-topic: the equation 22 in the LM5177 datasheet seems to be wrong. Instead of "1/2 I_in_avg" i'd expect "1/2 I_peak_peak". Please confirm.

Thanks in advance,

Al

  • 0
    TI__Prodigy 550 points

    Hi AI,

    Thanks for using E2E.

    Table 7-1 in the datasheet is the updated version. Please use that one when configuring your device. We will update the table in the EVM user's guide.

    In LM5177 device, "µSleep" is always there in the PSM. In LM51772 device, you can enable or disable "µSleep" in PSM. Please refer to chapter 7.3.2 in LM51772 datasheet for further explanation:  https://www.ti.com/lit/gpn/lm51772

    And about equation 22, you are right, it should be I_peak_peak, we will correct this typo.

    For the R_CFG performed on the evm, I will get back to you when the engineer is back. Thanks for your patience.

    Best regards

    Yezi

  • 0 in reply to Yezi Yang
    Prodigy 40 points

    Hi Yezi,

    Thanks for your helpful answer so far!

    Ok, i'll wait for the information about the applied R_CFG (and maybe EVAL board default R_CFG dip switch position?).

    BR,

    Al

  • 0 in reply to Al Hollmann
    TI__Guru 66700 points

    Hello AI,

    Please use the datasheet as reference for the configuration functions. At the end, there is no default dip switch position, you just put them into the position for the function you want to achieve.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 40 points

    Hello Brigitte,

    Thanks for your answer. So no default setting here - fair enough.

    But please let me rephrase my question:

    I would like to know the exact R_CFG setting(s) used for all the various measurement results in the LM5177 eval board user's guide, so i'd be able to correctly interpret their implications.

    Thanks and BR,

    Al

  • 0 in reply to Al Hollmann
    TI__Guru 66700 points

    Hello AI,

    The default connections for the jumpers can be found in table 2-2.

    DRSS is disabled, SCP and current limit cannot be observed during the shown measurements.

    The efficiency measurement seems to show no PSM entry. We will need to check this again when the responsible engineer is back in 2 weeks from now.

    Best regards,
    Brigitte