zhangz64
Junior Member level 3
Hi Everyone,
I am trying to understand the how to select decoupling cap effectively.
I see people put a lot of caps at input of their LDO or VDD of Analog IC to filter noise.
Those cap are put in parallel and value ranges from 10uF to 12pF, I understand that those caps are meant to target noise at different frequency since each cap has a different impedence vs Frequency curve, where the minimum impedance sit differently.
Also reduce ESR i think?
My first question is :
Is there a rule of thumb for list of value for those decouple caps ? like, 10uF+1uF + 0.1uF + 1nF ? or Do i need to understand the frequency distribution of the my board?
For example I am using a LDO(lP38511-ADJ) to supply sensitive analog circuit(16 bit DAC) and there is no Switch convertor and high speed bus on the board. the data sheet suggested minimum 10uF. Does it help to put more cap at input to get cleaner output?
or if i want to filter a input to 16 bit DAC that takes 3.3V, that from a LDO what is the normal cap values for decouple ?
My second question is related the cap selection on digikey.
I was design a LDO based on a dev board. (LP38511-ADJ). The dev board used a 10uF as decouple cap which is 1.6 USD by searching its part number
yet i can find a cap with same rating for 0.4 USD. (Same voltage rating, X7R,tolerance).
Is there any other important factors impacting the performance for the cap to justify this price difference?
Also, For 10uF, There are 0805 package and 1206 package for similar price. Does 1206 offer any advantage at all?
Thanks a lot for the help,
Eddy
https://www.digikey.ca/product-detail/en/avx-corporation/1210ZC106KAT2A/478-1625-1-ND/564657
https://www.digikey.ca/product-deta...ca-inc/CL21B106KOQNNNE/1276-2872-1-ND/3890958
I am trying to understand the how to select decoupling cap effectively.
I see people put a lot of caps at input of their LDO or VDD of Analog IC to filter noise.
Those cap are put in parallel and value ranges from 10uF to 12pF, I understand that those caps are meant to target noise at different frequency since each cap has a different impedence vs Frequency curve, where the minimum impedance sit differently.
Also reduce ESR i think?
My first question is :
Is there a rule of thumb for list of value for those decouple caps ? like, 10uF+1uF + 0.1uF + 1nF ? or Do i need to understand the frequency distribution of the my board?
For example I am using a LDO(lP38511-ADJ) to supply sensitive analog circuit(16 bit DAC) and there is no Switch convertor and high speed bus on the board. the data sheet suggested minimum 10uF. Does it help to put more cap at input to get cleaner output?
or if i want to filter a input to 16 bit DAC that takes 3.3V, that from a LDO what is the normal cap values for decouple ?
My second question is related the cap selection on digikey.
I was design a LDO based on a dev board. (LP38511-ADJ). The dev board used a 10uF as decouple cap which is 1.6 USD by searching its part number
yet i can find a cap with same rating for 0.4 USD. (Same voltage rating, X7R,tolerance).
Is there any other important factors impacting the performance for the cap to justify this price difference?
Also, For 10uF, There are 0805 package and 1206 package for similar price. Does 1206 offer any advantage at all?
Thanks a lot for the help,
Eddy
https://www.digikey.ca/product-detail/en/avx-corporation/1210ZC106KAT2A/478-1625-1-ND/564657
https://www.digikey.ca/product-deta...ca-inc/CL21B106KOQNNNE/1276-2872-1-ND/3890958