I was reading the datasheet of a switching powersupply RT8251. In the layout recommendations there is a statement -" Connect feedback network behind the output capacitors. Keep the loop area small. Place the feedback components near the RT8251" What does it mean by behind output capacitors. Consider the chip->Inductor->Output Capacitor->Feedback resistor tap point or is it chip->Inductor->Feedback resistor tap point->Output Capacitor A screen shot is attached. For that matter which is the apt point where I should tap the feedback resistor from the Vout ? enter image description here


1 Answer 1


They mean like this:


simulate this circuit – Schematic created using CircuitLab

Because there's a lot of current circulating in that loop between the chip Vdd or chip GND and L1/Rtrace/Ltrace/Count you don't want to take the feedback point before the capacitor- rather a kind of Kelvin connection so any voltage drop in that loop does not unduly contaminate the feedback signal. You also should keep the loop area for those two loops (switch on/switch off loops) as small as practical to reduce EMI and avoid other problems.


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