LM5146-Q1: WEBENCH® Tools/LM5146-Q1:

Hello

I will pass this to our controller engineers for help.

Thanks

Dinar,

Is your converter switching stable?

Is your Exposed pad underneath the IC connected to a copper pour for heat spreading? Do you have thermal vias there?

Please see related app note on PCB design: https://www.ti.com/lit/an/snva183b/snva183b.pdf

Hope this helps,

-Orlando 

Hello Orlando. Tell me please how can i check "converter switching stable" ?

There are thermal vias under ic, please look attached gerber files.

Project Outputs for LM5146Q.zip

Dinar,

Please scope shot SW node so I can see frequency & duty cycle to check stability.

-Orlando

Please look on it:

There are SW node shots without output load

Dinar,

SW node wave should be a square wave from 0V to VIN at switching frequency.

From your 23.7kΩ RT your switching frequency is 420kHz, Are you able to zoom in more? like 1µs/div.

Your layout around the IC is ok, you have a good amount of GND copper that should help dissipate heat.

Also your schematic is only orderable parts and difficult to check values, can you fill out LM5146DESIGN-CALC with your design?

Thanks,

-Orlando

here are some more detail vues, frequency is not stable.

there is no output load

Dinar,

Please try tying SYNCIN (pin 8) to GND to enable diode emulation mode. 

Also your schematic does not show values, please fill out and attach LM5146DESIGN-CALC so I can check it easier.

-Orlando