Dear All,
Please let me talk about the countermeasures for undesired oscillation of TPS5430 on the customer board.
Our customer confirmed an undesired oscillation of Vout on their board.
We attach the document which we summarized board layout and the oscillation waveform of our customer in.
Our customer is going to change the input capacitance. (from ceramic to POSCAP)
With the data sheet, it recommend the using the ceramic capacitor as an input capacitor.
■Question1
Is not there the problem even if customer use POSCAP for input? (What kind of problem is thought about?)
■Question2
Do you think the cause of undesirable oscillation to be what?
(We think whether it is a cause that ESR of the parallel capacitance of the output side is too low. Is there the Min spec of the ESR? )
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■Problem and its features
①An undesired oscillation of Vout was confirmed with a constant current.
(Especially, undesired oscillation is remarkable with the high load current.)
②In this case of ①, undesired oscillation might not happen.
Under the situation, this problem occurred when a customer cooled these parallel capacitances of the output side with a cold wind.
③Although the low load current, this problem occurred when its part was cooled.
■Their countermeasure
Customer tried a change of these input capacitances. (value/kind)
These points are C1235 and C1236 on customer’s block diagram.
Before：Ceramic capasitance 4.7μF
After：POSCAP 33μF
