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TPS54314 EVM "C1" capacitor

Atsu K
Prodigy 100 points
Other Parts Discussed in Thread: TPS54314

Hi, I'm looking at the TPS54314 EVM User's Guide (http://www.ti.com/lit/ug/sllu036a/sllu036a.pdf). 

In Section 1.3.4, it references the "C1" capacitor as the slow-start capacitor. However, in the schematic in Section 4.1, C1 is not attached to the SS/ENA pin which should be used for slow-start.  So my questions are

1) What is the C1 capacitor in the schematic for? 

2) Is it connected to PGND or AGND?

3) Similarly, on p8 of the TPS54314 datasheet, there's a same 1000pF "C11" capacitor in the Figure 10 reference schematic.  Is this also the same thing?

Thank you very much for your help.

  • 0
    TI__Guru**** 191445 points

    For the EVM, C8 is the slow start cap.  It is not installed.  Sometimes the example equations do not reference the actual schematic (but they should in my opinion).  In this case there is only one capacitor in the equation so it is referenced as "C1".  C1 in the actual schematic is a high frequency bypass capacitor.  The main output capacitor, C4 is an electrolytic type with 40 mohm ESR.  It is sometimes helpful to include a low value, low ESR ceramic cap in parallel to reduce HF noise on the output.  In the datasheet, C11 is the same as C1 in the EVM.