TPS54260: no12V output

Hi Betty,

Would you be able to share some waveforms? 

Can you include the VIN, VOUT, and PH waveforms for both cases, no load and 100mA load?

Thanks, Jason

Hi Jason,

add waveform result.

TPS54260.zip

Hi Jason,

add waveform result.

0045.TPS54260.zip

Hi Betty,

Thanks for sending the waveforms.

From your waveforms, it does not look like the PH voltage is switching. I expect to see a square wave from 24V to 0V and about 50% duty cycle. It looks like there is only a DC voltage on the PH node. Can you make sure that you are monitoring pin 10 of the device?

Looking at your schematic, why does the connection between VOUT and the feedback resistors look different than the other connected wires? Is this point connected?

Thanks, Jason

TPS54260schematicdocx.docx

Hi Jason.

I think the PH waveform is correct because the TPS54260 is work in light laod. TPS54260 operate in PSM mode.

for VOUT, yes, this point is connect to other circuit, but now we have remove this circuit, only leave TPS54260.

Hi Betty,

Can you take another waveform of VOUT and PH? I would like to see these waveforms at start up, when VOUT is rising.

Thank you, Jason

Can you also see if the PH node begins switching once the load is increased?

We also noticed that your feedback resistors are placed further away from the VSENSE pin. It is recommended to place the FB resistors close to the VSENSE pin to avoid noise affecting the regulation. Can you try moving the feedback resistors in your design to create a short FB connection?

Regards, Jason

Hi Jason,

customer will move feedback reistors to see if it help.

for PH waveform once the laod, you can see the video named PH-load change. once add load, PH change to a stable voltage and don't switching.

just to confirm, which condition the TPS54260 will enter to PSM mode? customer's PH waveform is correct without load, right?

Hi Betty,

I will to find out the current where the device enters PSM mode.

The PH waveform looks to be correct for PSM mode.

Regards, Jason

Hi Jason.

customer change the feedback resistor, but not help. how to do next?

Hi Betty,

Please monitor and record the VIN, VOUT, PH and SS/TRK pins at start up. 

Also, please take waveforms of the same signals when load is introduced.

Regards, Jason

Hi Betty,

Here is a good app-note describing ECO-mode operation. It describes how to determine the current where the device transitions to ECO-mode.

Regards, Jason