Timeline for Ferrite bead resonance
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 24, 2015 at 17:13 | vote | accept | Quentis | ||
| Sep 23, 2015 at 17:22 | answer | added | Spehro 'speff' Pefhany | timeline score: 3 | |
| Sep 23, 2015 at 16:22 | comment | added | The Photon | Reference design are never perfect, and some aren't very good at all. If you can make your design better than the reference design, then you should do that. | |
| Sep 23, 2015 at 14:27 | comment | added | Quentis | Unfortunately I haven't got any measurements right now. The model is not bad in my opinion it gives back the impedance curve in the datasheet. The saturation is not modeled however and maybe the very high frequency behavior is different too but this is a low frequency phenomenon. Maybe we can agree in that ferrite beads are inductors on low frequency and if it is the case a resonance frequency might occur if the dampening is not right. 140uF capacitor removes the ringing but it is huge.Also a 10uF capacitor series with 1 Ohm resistor parallel to 100nF cap removes resonance too.(dominant pole) | |
| Sep 23, 2015 at 10:19 | comment | added | user16324 | Does a real measurement show the same resonance? What effect does changing the capacitance (C214) have? There is usually no downside to improving the decoupling on an analog or PLL supply. | |
| Sep 23, 2015 at 10:01 | comment | added | corecode | Your model of the ferrite is very crude. Additionally, does the voltage rail slew rate reflect reality? | |
| Sep 23, 2015 at 9:59 | comment | added | Quentis | Sorry I wanted but I pushed the enter acidentally. ipblox.com/pubs/Ferrite_beads/… | |
| Sep 23, 2015 at 9:56 | comment | added | efox29 | You feel that these documents which describe your problem are not worth posting for someone to answer your question, about why this is happening ? no ? | |
| Sep 23, 2015 at 9:54 | comment | added | Quentis | There are some documents which mentions these problems. The problem is a 3.3V rail is pushed by 6V voltage. Plus if there is any noise source on the board which causes some spikes on 300kHz then it is amplified on the resonance frequency. (so this filter is garbage on 300kHz) Actually it is worse on 300kHz than if it wouldn't there at all. | |
| Sep 23, 2015 at 9:33 | comment | added | efox29 | And what is the problem exactly ? Is it your simulation or your real world measurements ? | |
| Sep 23, 2015 at 9:32 | comment | added | efox29 | Reference boards are for a particular layout and stackup. A reference design is not guaranteed to work exactly as is, if you change anything from the original design. | |
| Sep 23, 2015 at 8:56 | history | asked | Quentis | CC BY-SA 3.0 |