UCC2897A: Frequency mismatch issue.

Hi,

Please provide zoom-in the 750kHz portion waveform so details can be seen, for example to show about 10 switching cycles in on the oscilloscope for 750kHz after zoom in.

Hi,

Please check the zoom-in the 750kHz portion waveform as below,

Rgds

Hi,

The pulses are stable with fsw 750kHz. Please check below:

check RON, ROFF and RDEL resistors to make sure they are soldered properly. As fsw is only related to these resistors so if solder not solid or not clean then fsw can be affected.

Check these resistor values to make sure they are good resistors or change them to new from different resistor producers.

Change to new UCC2898A (typo error and it should be UCC2897A) device in case the one used already damaged. Also make sure the IC soldered properly.

By the way what are these three resistors values?

Hello,

In above waveform,

Orange colour represents voltage at OUT Pin, Blue Colour represent voltage at Ron Pin and purple colour waveform represent Voltage at Roff pin.

Here, if we neglect the noise, the constant value are measured  2.66V at Ron pin and 2.9V at Roff pin.

We also verified Ron and Roff  resistor values after taken out from PCBA and found ok 

Even if Resistors are not selected properly, then also voltage at this pins should not exceed 2.5V as per datasheet.

Rgds

AM

Hi,

As I suggested, replace the unit with a new to see if the issue can be resolved since the unit might be damaged.

Hi,

As you suggested to change new UCC2898A parts, however I am unable find the part with P/N : UCC2898A in TI website.

Can you send the weblink of datasheet /application note of  P/N : UCC2898A ,which you asked to changed

Thanks

Rgds

AM

Hi,

Sorry, that is a typo. I mean UCC2897A same as you are using but a new unit.