Good day!
I received the video converter test sample very late. After research, I found out that DCDC MP9943 voltage ripples with a frequency of 390…410kHz fall into the Video range of the PAL format signal - this creates artifacts on the video. The frequency varies slightly with the body temperature. It gets better when either the frequency goes beyond the 380< DCDC >410kHz range or when I add an extra LC filter to the board.
Tell me, is there any pin-2-pin chip for MP9943 with a different sample rate? Maybe you can tell me how to get away from obstacles on Video more easily?
Thank you.
Hello @tararoev_dl,
Welcome to the MPS Technical Forum! Unfortunately, there is not a pin-2-pin replacement for the MP9943 with a different fixed frequency. Some possible solutions to your issue could be using the SYNC control pin on the MP9943 and using an external clock to switch outside the PAL frequency band. The MP9943 can synchronize from 200 kHz to 2.2 MHz with an external clock but is fixed at 410 kHz nominally.
If this solution does not work for you, please let me know and I can suggest another DC-DC converter that can fit your application.
Best,
Ryan
Thank you for the reply.
We used an external generator and confirmed the impact of the DC-DC converter’s operation on the video signal. Unfortunately, the PCB design does not allow for a fix.
There is an example where the video chip is rotated by 45 degrees, which made it possible to increase the distance from the DC-DC converter.
Could you suggest a type of inductor that has less electromagnetic interference in its vicinity?
Best regards,
Dmytro.
Hi Dmytro,
Shielded and semi-shielded inductors are meant to limit EMI interference between parts and can offer a solution to your issue. While there are many vendors that sell shielded inductors, MPS has its own line of inductors that are tailored for our DC-DC applications. Please see the link provided: Inductors.
Best,
Ryan