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Design Clarification

Mahsheed , 08-19-2020, 02:37 AM
Hi, Please check the attached picture of FM8301 IC. Its basic purpose is to turn on/off the MOSFET to control the inductor current. Now, I am confused, what is the purpose of the capacitor that is placed across the output (LEDs). Its not the design of Buck Converter, and some designers of boards just skip this capacitor. Can anyone please explain its functionality?
Thanks in advance.
robertferanec , 08-24-2020, 04:42 AM
Please what is the full part number of this chip? When I google for FM8301 I can not find a standard manufacturer nor datasheet on a manufacturer website.

PS: In the search results, there are only some links pointing to alldatsheet.com ... not a good sign. This is telling me, that I do not have the full part number or .... if that is a full part number, then this is telling me that I should not use this component in my designs.
Mahsheed , 08-24-2020, 05:10 AM

Its Chinese company and datasheet is also in Chinese. Please find attached the datasheet.
qdrives , 08-24-2020, 12:24 PM
Yes, I found the Chinese data too. Google translate is unable to translate it.
Here are my 2 cents:
The capacitor parallel to the LEDs will make the LEDs light more constant (less blinking). Check LED lighting with mobile phone camera, then you may notice the blinking.
I had such lighting in an electronics workbench - terrible!
My advise would be to place the capacitor.
robertferanec , 08-25-2020, 12:20 AM
I agree with @qdrives
Mahsheed , 08-26-2020, 02:58 AM
What I wanted to confirm is if that has some link related to buck converter design? In my opinion, it should not be, as there the capacitor works as low pass filter. Also if the capacitor is only linked with the blinking of LEDs and does not link with the board to burn, then blinking would not be a major concern.
qdrives , 08-26-2020, 11:05 AM
Yes, it is like a buck converter. If the AC input is 230Vac and you are driving some LEDs with it, the 'control' will be more difficult without capacitor.
Mahsheed , 10-02-2020, 04:13 AM
I think the other capacitor is just for the time duration when the MOSFET is off and no current is flowing through it. At that time capacitor provides external voltage to the LEDs. What do you think?
qdrives, 10-02-2020, 01:22 PM
Correct, but that is also the case for switch mode power supplies.
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