TPS65130: the positive voltage has a drop during start up

Hi Jay,

Will this drop still exist if you disconnect the load when powering on the device?

BR

Patrick

Hi Patrick,

Yes, without load , this drop still exist . 

But I found the rootcause is that the difference between input and output voltage is too small today . 

After I add the difference , the drop dose not exist.

Hi Jay,

Could you please share the new waveform of VPOS?

BR

Patrick

Hi Patrick,

Below is the new waveform:

Hi Patrick

I tested the waveform of VSP and VSN with five TPS65120 on the same board.

I found that three of them have a big step and the other two have a tiny step(Same waveform as above). 

How can this step be eliminated ？

Hi Jay,

This step is as expected for a boost converter. The first step is when you powering on the device, the Vin will charge the output capacitor first and at this time, boost is not switching. When boost starts switching, the Vout will ramp up to the programmed value finally.

BR

Patrick

Hi Patrick，

I try to adjust C21 from 10nF to 2.2nF , this step can be reduced.

In the spec, the recommended value of C21 is 10nF .  

Are there any potential risks after C21 adjusted to 2.2nF ?

BR

Jay Li