TPS650250 Input Filtering

Q: TPS650250 Input Filtering by 7382

Can I use a high frequency ferrite bead in series with the input voltage feeding the buck converters. I want to connect the VIN and the LDO input to the source side (left side) of this bead. Please advise if there is any reason that they should do something different than this. Thanks.


Q: Re: TPS650250 Input Filtering by 10449

If I understand correctly, you are adding an inductor between the input capacitors to the TPS650250 and the VINDCDC1, VINDCDC2, VINDCDC3, and VINLDO.  You can NOT add extra inductace between the input capacitor and the IC.  If you want to provide additional filtering, you can layout your design per the EVM recommendations and then add the ferrite bead outside of that design.  In other words, connect the ferrite bead between the input voltage comming into their board and the input capacitors to the power supplies.  For buck converters, one of the most critical component placements is ensuring the input capcitor is located as close to the power FETs as possible with the smallest inductance in the loop as possible.  The "loop' is the path from the input cap, through the power FET, through the synchronous FET (or diode) to ground, and then back to the capacitor ground.