A small, external filter capacitor is recommended on the CS pin. Track the filter capacitor as directly as possible from the CS to GND pin.
Referring to Figure 44, a series resistor such as R5 is typically connected between the current sensing resistor R16 and the CS pin to form an R-C filter. A filter time constant between 100 ns and 200 ns is recommended. If the filter time constant is made too large, the filtering causes the transformer peak current to exceed the control loop demand level, which affects regulation and standby power. Place resistor R5 as close as possible to the CS pin.
Reduce the total surface area of traces on the CS net to a minimum.