TPS2412: What to do if my FET Ciss is lest than 1nF data sheet recommendation

Robbie Valentine86

Part Number: TPS2412
Other Parts Discussed in Thread: MSP430FR5969

Hello,

My schematic is attached.

Questions 1:

Per section 8.3.6 TI recommends that a fet with 1nF Ciss or greater is used. I'm referring to the first of the three bullet points. My load is very light and because of that I'm using the PMPB215ENEA N-Channel FET. This has a Ciss of ~215pF. What should I do to make sure my TPS2412 is stable and operates correctly with this FET?

Question 2:

Per the second bullet in section 8.3.6, does every TPS2412 circuit require 100uF ceramic output capacitance? I'm wondering if I need to add this as my load is very light (basically an MSP430FR5969 and some peripheral digital circuitry). Right now my output is 4.7uF which is way off according to this statement in the datasheet.

Screenshot of the bullets from the datasheet I'm referring to.

over 5 years ago

0 Karikalan Selvaraj over 5 years ago

TI__Genius 16305 points

HI

I am looking into this and will get back shortly.

Regards,
Kari.

0 Robbie Valentine86 over 5 years ago in reply to Karikalan Selvaraj

Expert 1550 points

Thanks Kari!

0 Karikalan Selvaraj over 5 years ago in reply to Robbie Valentine86

TI__Genius 16305 points

Hi

One way to improve stability is to add ESR to the capacitance on the cathode.

1uF in series with a 1ohm intentional ESR could help to remove the oscillations.

Let us know if this helps out.

But, for such a small current what is the benefit of using MOSFET, simple diode could server the purpose.
Are you concerned about the forward drop?

Regards,
Kari.

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TPS2412: What to do if my FET Ciss is lest than 1nF data sheet recommendation