TPS54917: TPS54917 Low side mosfer Negative Spike

Kao Mick

Intellectual 330 points

Part Number: TPS54917

Hi SIR

We use tps54917 to design 3.3V to 1.0V_9A power supply for asic use.

A phenomenon was found during the measurement.

As long as the inductor current enters the continuous conduction mode (about 1A),

Low Side Mosfet_Vds shows obvious negative spike and exceeds the maximum absolute value of the specification.

How can we improve this phenomenon?

over 4 years ago

0 Dorian Brillet de Cande over 4 years ago

TI__Genius 14876 points

Hello Kao,

What you observe here is normal behavior of TPS54917, phenomenon is well explained in the following App Note.

http://www.ti.com/lit/an/slva494a/slva494a.pdf

Let me know if you have any questions.

Thank you very much!

Regards,
Dorian

0 Dorian Brillet de Cande over 4 years ago in reply to Dorian Brillet de Cande

TI__Genius 14876 points

Hi,

I haven't heard back from you. Do you have any further questions on this topic?

Thank you very much!

Regards,
Dorian

0 Dorian Brillet de Cande over 4 years ago in reply to Dorian Brillet de Cande

TI__Genius 14876 points

Hello,

I am closing this thread due to inactivity.

If you have any further questions, please reply below.

Thanks a lot!

Regards,

Dorian

0 Kao Mick over 4 years ago in reply to Dorian Brillet de Cande

Intellectual 330 points

HI SIR

I discussed this issue with the local ti fae. He also explained to me that this is the phenomenon that the inductor current appears through the flywheel diode when it is dead time, but this phenomenon is not written in the spec. This makes us feel a little confused.

0 Dorian Brillet de Cande over 4 years ago in reply to Kao Mick

TI__Genius 14876 points

Hello,

Thank you for this valuable feedback!

I talked to FAE to explain this phenomenon. This is normal operation and inherent to its design.

In the datasheet you can find explanation on Dead-Time Control and specifications, figure 15 show you behavior on the PH node.

It could be more explicit how this part behaves at very low-load, especially on the SW node.

TPS54917 is not our latest device and is not optimized to work at very low-load. I can recommend you newer devices which are more optimized to work at low and high loads if you need.

Let me know if you have any questions here.

Thanks again.

Regards,
Dorian

Power management

Power management forum

TPS54917: TPS54917 Low side mosfer Negative Spike