LNK304 overshoot when Drain-Source turn off

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Hi there,
have a big problem with the strong overshoot of the "Source" connection of LNK304 when switching off the DS transistor.
This leads to interference in the transmitter (868MHz).
Tried different output capacitors (55, 100, 150, 360, 500 mOhm). The same applies to various inductors. A Wurth 680uH (744 777 26) is currently installed.
Can someone help me with this?

첨부 파일Size
Sch.33.76 KB
Source Pin69.34 KB

Hi tidoretan,

Can you send a picture of your PCB layout file? Also how far is the transmitter with respect to the LNK304 board?

I suggest minimizing the length and width of the SOURCE copper area, as this is the nosiest voltage in the circuit. Also ensure that critical loop is kept as small as possible.

Hi PI-Jango,

1. It's a "sandwich", with Transceiver on the top. Distance r. about 2.5cm.
2. 33pF capacitor at FB helped me to reduce the steepness of the falling edge

thank you,
tidoretan