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Feedback path for TPS40305

Bruce Warkentin
Prodigy 30 points 
Our design has the Vout connected to the FB pin (close to the TPS40305) though the datasheet's recommended RC network.  Are there any issues in moving the Vout feedback point connection closer to the point of load?  I am seeing too much drop in our power distribution. Other power modules I have used have a sense line which specifically has that intent...

How much voltage drop can the feedback mechanism compensate for.  We currently have about 70mV drop with a 3A load but we are not fully loaded yet.

thanks much

Bruce

  • 0
    TI__Genius 11095 points

    Hello, this should be fine.

    The major concern is noise pickup along this line, you have to be careful not to route it near the driver signals, boot, SW nets, and keep it out of the high dV/dt, dI/dt "loops" on the layout. My suggestion would be to keep the RC components local to the controller, and route a single sense line from VOUT at the load, back to the controller. You may also want to look at adding more copper plane etc... for the output voltage, since you've got about 20 mOhms of PDN resistance, from your observation. 

    Another option would be to either add an external differential remote sense amplifier with an op-amp, or even use a controller with one integrated.