TPS54331-DC2DC Voltage Output

[tiwari.sachin]

I have designed a DC to DC that has input of 12 to 18V and output at 8.5V.

Following is the schematic used

I am getting the desired result but when I measure the output, I am getting the following result

The output rise isnt smooth as expected.

What could be causing this or am I doing something wrong on the schematic side.

Regards

Sachin

 

[KlausST]

Hi,

Please use the [insert Image] button or use [Ctrl]+[P] to upload pictures.

What does "isn´t smoot as expected". --> please tell us what you expect. Draw a sketch.

Switch mode power supplies need careful PCB layout design to operate properly. -->Show us your PCB layout.

Klaus

 

[tiwari.sachin]

Hi,

I was expecting the output curve for the given schematic as below

--- Updated Dec 13, 2023 ---

Schmatic and Output curve that I am getting is attached.

 

[KlausST]

Hi,

if you want a start upt ime of more than 20ms as shown in the "output_expected" picture, then use Formula 3 of the datasheet.

I expect the correct SS capaciotr will bring some benefit.
But the start up ripple most probably is caused by a bad layout ...
Also critical is capacitor, inductor, diode selection. We don´t see what exact parts you did use. Hopefully you followed the datasheet guide.

If you want me to give more detailed feedback: Provide the missing informations.

Klaus

 

[tiwari.sachin]

Hello,

I have attached the various waveforms I tried and also the routing of DC2DC Section (Bottom is mirrored so that understanding of routing can be easy in image)

--- Updated Dec 13, 2023 ---

I expect the correct SS capaciotr will bring some benefit.

Signal shown as "Expected Signal" is only for reference. I am ok with the rise time of output I am getting

 

[FvM]

I wonder if the DC/DC is loaded with actual output current in your test. For me it looks like a badly compensated control loop (gain to high).

 

[KlausST]

HI,

removing C6 is counter productive.

I´m talking about the SS capacitor. C15. --> don´t remove it. Calculate the correct value. I expect a bigger value.

Btw: If you do multiple scope pictures: please keep horizontal and vertical setup .. for them to be compared more easy.

Klaus