TPS54260: buck mode light load

Hello Engindi

To help debug, could you share the waveforms at following nodes

1. SW
2. Vout
3. BST-SW
4. Comp

Thank you

Regards

Onkar Bhakare

please find waveforms at , Input voltage is 26V 

1.     NO load

2.     .05A load

3.     .055A load

4.     .06A load

1.  No load 

   Without load SW

  Without load Vout

   Without load Comp

  Without load BST-sw  

2. .05A load 

 50mA Load Vout

 50mA Load BST-SW

 50mA Load SW

 50mA Load Comp

3. .055A load

 55mA Load Vout

 55mA Load SW

 55mA load Comp

 55mA Load BST-SW

4.  .06A load = Vout going 0Volt

 60mA load BST-SW  output-0V.

 60mA load Comp  output-0V.

efficiency around 50-54%

Thanks engindi for update

One thing, when load is connected(60mA) and we give power to the IC direct 26V then IC burns.

What can we do?

Hello Engindi

Could please check with placing an electrolytic capacitor of 100 uF at the input for damping? See if it helps. Additionally, reduce inductor value to around 100 uH, currently it is quite high, it will reduce effectiveness of current control.

Let me know if this helps

Thank you

Regards

Onkar Bhakare

Hi, In my project we cannot use WET capacitor and DRY capacitor till 100uF quite expensive and there is also space issue so we cannot use more than 10uF 

We tried 100uH and found efficiency to be around 80% at 60mA and again after trying 3 times, IC got burnt on direct load and thermal PAD, GND, Vin, SW pins got shorted. ( with 300uH found 90% efficiency at 60mA)

Hello Engindi

Could please share you layout files and image of the test setup also?  It looks like case of Electrical Overstress (EOS) to me. Additionally, could you please probe Vin and SW with high bandwidth probe? 

1. You can set trigger at Vin, while applying the sudden input. Probe SW and Vin together 
2. Set trigger at Vout while applying the sudden load. Probe SW and Vout together

Moreover, share the part no./datasheet of inductor

Thank you

Regards

Onkar Bhakare

Hello Onkar , 

PCB layout for the entire project is under process, I will share with you once completed.

As of now I am using Zero PCB for IC testing.