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Original question:

LM3102 Output Regulation Issues

LM3102: Allowed output voltage range

Michal Sir
Prodigy 10 points
Part Number: LM3102
Other Parts Discussed in Thread: LM20242

Hi Ti,

I am facing light load regulation issues with LM3102 - output voltage 12.5V, input voltage from range 15-30V. Voltage goes up to 14V at the DCM condition, IC feedback is not reacting according to the datasheet - new Ton cycle is starting sooner than FB drops below 0.8V.

In this post, similar issue is noted: 

(+) LM3102 Output Regulation Issues - Power management forum - Power management - TI E2E support forums

TI, I would like to ask you - is the operating output voltage range really limited to 0.8-7V? 

Thank you

Regards

Michal 

  • 0
    TI__Guru 71105 points

    Hi Michal,

    Thank you for posting.  I consulted other team members, and also read the old E2E thread that you referred to.  It appears that the output can be well regulated for the range between 0.8V and 7V.  In your 12.5Vout target, it should work but the regulation may become less accurate due to the reasons mentioned by the previous technical owner in that old E2E thread. The larger ripple seems to be lack of ripple injection.  Could you also try the design tip shown in http://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-components-files/858/1258._5B00_E2E_5D00_-David-Planthaber-LM3102.pdf?

    I also learnt that the device LM24220 can be used as a replacement but it can support higher output voltage up to 24V.  You may take a look at it, too.

    Thanks,

    Youhao

  • +1 in reply to Youhao Xi
    Prodigy 10 points

    Hi Yuahao Xi, 

    thank you for your quick answer, I tried this circuit already and only slight improvement was achieved - at light load output voltage reaches almost 15V, which is not acceptable. I think the major problem is behavior of the IC , which is clearly not respecting 0.8V threshold to start new cycle but instead of this enters OVP mode at 0.92V (resulting in approx. 14.5V output voltage).

    TI should state this recommended output operating voltage 0.8-7V in the datasheet.

    LM24220 - Does not exists, can you provide link pls? did you mean LM20242?

    Regards

    Michal 

  • 0 in reply to Michal Sir
    TI__Guru 71105 points

    Hi Michal,

    Very sorry for the typo. The p/n is LMR20242.

    Thanks,

    Youhao