TPS53319 Coil gets hot

No idea?

Maybe my output capacitance is not perfect ? (2x330u aluminium caps)

Maybe the coil does not accept 500kHz of switching? Maybe the inductance is too high?

Greets

Can we see your schematic and a waveform of the switching node?

Hello,

ready or not, here it comes. I used this output capacitor, maybe too much ESR ?

http://www.mouser.com/ds/2/420/17065026404d9b18b987fcb-7468.pdf

The 6.3V at the input capacitor is labeled wrong. Its actually 25V rated.

Greetings

Switching1

Switching 2

I can see a couple things.  What is the purpose of C4?  I would first remove it.  The calculated ripple current is 2.48 A.  Each of your output capacitors is rated for 1.19 A.

Hello,

i can not see C4 on this schmatic. The Ripple thing will befixed. What about the ESR ?

is the calculated value of ESR in the Datasheet a min. Value? Or a value that should be used? I also can not find the MOSFET On resistance value in the datasheet Rdson.

early morning typo...C24.

Hehe ok. So good morning John.

The reason for this capacitor is, I used the TPS53319 TINA-TI Transient Reference Design for simulation. The component was inset by default. The simulation looked good so i took it. Anyway i removed that component now in my device. Don't know if that changed a thing. Can you please answer my question from above?

Greets

Surprisingly, RDSon is not specified.  The ESR is referenced in a few different equations.  Which one were you asking about?

Huhu,

i need Rdson for EQ (7). And i use EQ (8) for the ESR Calculation. I use the (L/fFS)/60 part. For my 4.7uH and 500kHz i get an ESR of ~40mOhm for the capacitor. Is that a minimum value they should have, or a fix value they should have? Because i think my caps has at least ten time the value.

I didn't write that datasheet.  It is a little confusing, but you don't actually need to know RDSon.  You can substitute Rtrip(kohm)/12.3 for Vtrip/32RDSon in EQ 7.  Backing that out of EQ 3, you can solve for RDSon of 3.8 mohm.  Sounds about right for NexFETs.

I'll have to reverse engineer EQ 8, it is not obvious what they are trying to do there.  I may not get to it this weekend unless I get tired of watching hoops :-)

I looked at that equation.  It looks like minimum ESR to generate at least 10 mV of ripple at the feedback pin.  I do not know why they need the (1-D) factor though.

Huhu,

i do not find any 330uF Cap with that rated ripple and the min ESR.... Can i use a polymer cap with lower ESR which has highter ripple rating? But its Only ~40mOhm per Cap and i have 2 parallel...

The important thing is the fed back ripple.  If you cannot find suitable capacitors, then you can always decrease teh inductor value instead.  the reference design of figure 2 uses 2 x 330 uF and 0.5 uH.  Alternately you culd inject ripple with an R C network as shown in figure 1 and equations on page 23.

Thank you. Guess i am going to try the MLC1250-132M 1.3uH coil with the Nichicon  PCV1D331MCL1GS Polymer cap.

I made a small calculator for the Bulk Output Capacitors solution, maybe usefull to someone else.... (no guarantee here)