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Original question:

TPSM365R3: Webbench efficiency deviation

TPSM365R3: Webench efficiency and frequency values

Neil Arnold
Prodigy 60 points

Part Number: TPSM365R3

Tool/software:

I have a circuit designed using the Webench tool. 14.5V input, 6.5V output at 200 mA operating up to 70C ambient using the TPSM365R3R (not FR) device. The details are in the attached PDF generated by the tool.

Recently, due to devices that don't seem to provide that expected efficiency or output voltage under load, my attention has been drawn to a related post for this part:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1358313/tpsm365r3-webbench-efficiency-deviation?tisearch=e2e-sitesearch&keymatch=TPSM365R3#

So my first question is: Was the webench updated per the issues raised in this post (as it appears to be generating the same model as when I first designed this circuit 18 months ago)?

Secondly, my attention was also drawn to Table 9-6 of the datasheet.  This seems to suggest that accepting the 1 MHz default frequency from the Webench may be insufficient for reliable operation of the part.

So my second question is: Do I need to increase the frequency (say to 1.2 or 1.4 MHz) to increase my reliability?

Lastly, I would ask: Is there a better tool (than this table or the Webench output) or available formula for estimating the best case operating frequency and efficiency?

6p5V0p2A365R6.pdf

  • 0
    TI__Genius 15670 points

    Hi,

    The efficiency numbers from Webench does seem to be off. However, I noticed that for TPSM365R3F the numbers seem reasonable. At 200 mA both F version and non-F should behave similarly. So you can use the TPSM365R3F in Webench. 

    The frequency recommendations are based on the inductor current ripple. At 1 MHz, for 14.5V to 6.5V, the inductor ripple comes out to around 360 mA peak to peak which is quite high. While this shouldn't cause any critical issues at 0.2A, this is much higher than recommended and can affect the ripple, efficiency etc. I would suggest increasing the frequency following the datasheet table, to around 1.6 MHz

    Regards,

    Niranjan