TL5001A: Trouble with external MOSFET driver

Hello,

I use TL5001 for a long time without any trouble, but I use this PWM controller without any external MOSFET driver. A new design requires a better efficiency and I have tried to use the circuit I have found in "example of application with the pulse width modulator TL5001" (SLVAE05, page 9). Indeed, input is 28V/10A, and output can reach 200W. Feedback is a resistor network between Vreg and PowerGNDout.

Whit no load, I obtain expected voltage. But when current increases, voltage falls (until 0V when current reaches 1A...).

I have tried to remove the field effect transistor, to change some resistors without any result.

I have found in SLVA034A three designs and I don't understand where is my mistake.

All help will be welcome.

Best regards,

JB