TPS54260: TPS54260 overcurrent protect when Inverting Power application

Hello Jack

I would need your help to understand the issue clearly. 

--when power up of +24V input, IC will be into overcurrent fault at once.

Does it mean device went into current limit momentarily and came out of it?

Is there any load on at output other than LED during startup?

Could please share the waveform indicating the issue?

Thank you

Regards

Onkar

Hi Onkar,

Delta used this device for several years, only reported this issue recently. and there is no new PCN after my check.

Based on Delta R&D feedback that there is no PWM output when power up ( Vinput = +24V.), and customer test it with no load, it is same.

Can you support the following questions firstly:

Q1:  Help check the parameter in Delta's schematic is reasonable based on their application (In Excel document.)

Q2:  What's the difference the following two top mark IC?

Regards,

Jack

Hello Jack 

I have one comment their schematic. compensation components need improvement. Rcomp(RR3) value is bit small and Chf(CR13) looks pretty big. They can use values suggested by the quickstart calculator. Rest of the schematic looks fine to me.

Two ICs shown in picture are sourced from different assembly sites but functionally, both are same. To get more information about the ICs, could you please share the lot no. or label for the left one.

Thank you 

Regards

Onkar

Hi Onkar,

Delta changed RR3/ CR13 based on the values from our calculator tool, but this problem can't be fixed.

Do you have a TPS54260 Inverting power EVM to repeat this issue?

And I plan to on-site check this issue next week, do you have some debug tips for me?

Regards,

Jack

Hello Jack

TPS54260 EVM (TPS54260EVM-597) can configured in the following way to make it inverting buck boost.

 I'll provide you my suggestions for testing on Monday. As I am out the office today.

Sorry for the inconvenience

Regards

Onkar  

Hello Jack

Try probing following nodes to understand the issue.

1. SW node w.r.t Vout
2. Voltage across CR2
3. SS pin voltage w.r.t Vout
4. Inductor current
5. GA w.r.t Vout

Thank you

Regards

Onkar

Hello Jack

Let me know when are going to conduct experiment. If possible, we can connect online over webex while you are testing.

Thank you 

Regards

Onkar

Hello Jack 

Any update on this?

Thank you

Regards

Onkar Bhakare