Original question:
Hi Team,
I have a question about Cbulk of TPS2372.
Due to board size limitation, my customer wants to reduce Cbulk value or remove Cbulk if possible.
PSE Type is 3,4.
Regarding Cbulk, I got following questions so could you help?
Question 1
What is the purpose of Cbulk? How does Cbulk work?
Question 2
is it possible to reduce or remove Cbulk and what is the problem if there is no Cbulk?
Question 3
How to calculate Cbulk value?
Regards,
Kai
Hello Kai,
Question 1
What is the purpose of Cbulk? How does Cbulk work?
- The purpose of Cbulk is to help with the transient response when the DC-DC converter is started. Initially, the IC keeps the DC-DC converter off during detection and classification. Then when the PSE applies full power the Cbulk cap is charging. Once the IC turns on the DC-DC, the Cbulk capacitor should be fully charged to handle that transient.
Question 2
is it possible to reduce or remove Cbulk and what is the problem if there is no Cbulk?
I suggest having two 47uF caps in parallel for Cbulk. That way you could try populating only one, but not loose any development time if both are needed. The converter won't startup without it.
Question 3
How to calculate Cbulk value?
There is not a specific calculation, but here is a table to aid in choosing. Please follow my suggestion above.
If this post answers your question, please indicate so by marking this thread as resolved. Thank you.
Regards,
Michael P.
Applications Engineer
Texas Instruments
