TPS54140A: Vout Ripple in case of a small Load (pulse skip mode)

Toshiya Asai

Part Number: TPS54140A

To reduce a ripple of TPS54140A in very small load (～less than 50mA) situation, I will choice a low inductance value(4.7uH). Is that OK ?
The inductance value calculated by the equation of Lo(min)(in 8.2.2.2 Output Inductor Selection (Lo)) is large (in case of lower Iout). But in case of pulse skip mode, this equation is not appropriate. Is that correct ?
If there's some advice about the capture shown below, Please let me know the point exactly. It would be great helpful.

over 6 years ago

0 Robert Blattner over 6 years ago

TI__Expert 6245 points

Hello user4778976,

You are correct, the maximum current in the equation is the part’s rated maximum, 1.5 A, not your typical load, 50 mA. 4.7 uH may be OK depending on your output voltage. Note that your inductor should be rated to saturate above 3 A if you want good short circuit behavior.
Could you share your basic circuit, including Cout, Lo, Vout, and compensation?

Also, could you try attaching your images again, they are not visible. I find that .png format works well when uploading images.

Regards, Robert

0 Katelyn Wiggenhorn over 6 years ago in reply to Robert Blattner

TI__Genius 11040 points

Hello,

I want to follow up on this post. Would you be able to share your basic schematic and images?

Best Regards,
Katelyn

0 Toshiya Asai over 6 years ago in reply to Katelyn Wiggenhorn

Prodigy 180 points

Hello,

Here is the circuit on our board.

The inductance value is originally 33uH, but it outputs long cycle ripple. 4.7uH is OK.

Regards,

0 Katelyn Wiggenhorn over 6 years ago in reply to Toshiya Asai

TI__Genius 11040 points

Hello,

Thank you for sharing your schematic.

As Robert said, this may be okay. You will want to verify the stability of this design for your range with loop response measurements. You can also use the circuit calculator tool in the product folder to verify the component choices as well.

Best Regards,
Katelyn

Power management

Power management forum

TPS54140A: Vout Ripple in case of a small Load (pulse skip mode)