LTM8002IY#PBF giving 2.6V every time even Rfb and RT Resistors are changed

There are two ways to quickly check the FB divider.

1) Measure the FB pin voltage and verify it is within the spec'd 0.95V - 0.98V range.  Then remove your FB resistor and measure the resistance from Vout to FB and verify that it is about 100kOhms.

2) Alternatively if you have limited equipment, you can set the FB and RT resistors for the 0.97V configuration and see if the output voltage measures 0.97V

Either of these options would be a good first step in narrowing down the location of the issue.

First Thanks for your reply.

I have measured the FB Pin voltage is coming around 0.47 V. And resistance from Vout to FB is 100K is coming.

As FB pin voltage is 0.47 only what can be the issue?  Please help.

Thank you

The next step is to measure your TR/SS pin voltage.  The TR/SS pin can be used for tracking (see "Output Voltage Tracking and Soft-Start" from pg 19 of the LTM8002 datasheet)  If the TR/SS pin voltage is stuck at 0.47V, then it is limiting your output voltage.