LM5176: Schematic and PCB review

HI Noel,

thank you for using the E2E forum,

You can use the private Email on the forum to send the schematic. (Click on my name - send private message)

Please drop a note here once done, as I am not as regularly checking the forum inbox as the forum content.

Best regards,

 Stefan

I have shared the required files. Please check your chat

HI Noel,

the phase margin with 40 Degree is very small - recommend to go over 60 Degree - please check over the full input voltage range - could not do the check as the attachment was only a pdf

connection of VIN is wrong

The current sense in the schematic shows 3 times 1k

Recommend to add a 0Ohm series resistor into the Gate lines of the MOSFET, in case need a resistor could be placed there.

Recommend to add a placeholder for a snubber on SW1 and SW2. So components can be placed if required, e.g. due to EMI

Move FB connection behind the big bulk cap - may add another small cap behind  that as well

Best regards,

 Stefan

By SW1 and SW2, do u mean (Q1 and Q2 as it is on my schematic) or both the high side switches (Q1 and Q3)?

Hi Noel,

put them from the SW1 to GND and from SW2 to GND - close to the MOSFETs.

Best regards,

 Stefan

Aha ok got it! i thought you meant the mosfets. Got it cleared now. I will get back to you soon after the changes and with the PCB

THANKS for now!

Hi! I've forwarded you the PCB . Please check the chat 

Stefan Schauer Please do check

Hi Noel,

Note: for a layout review we typically need 2-3 days. 

So here we are:

- it looks like the ground plane is split from left (controller) to power stage.
This will limit the grounding of the LM5176
- the Current sense resistor should be connected via a Kelvin connection to the CS and CSG pins

- PGND (Pin 19) should be directly connected to the decoupling cap C19

- Connect all AGND ground related components to the AGND pin directly

- do you have vias on the Thermal pad to connect the Thermal pad to the GND layer for Thermal connection.

Please check out the layout recommendations in the datasheet chapter 10.

And also this article gives many recommendations:

https://e2e.ti.com/blogs_/b/powerhouse/posts/four-switch-buck-boost-layout-tip-no-1-identifying-the-critical-parts-for-layout

https://e2e.ti.com/blogs_/b/powerhouse/posts/four-switch-buck-boost-layout-tip-no-2-optimizing-hot-loops-in-the-power-stage

https://e2e.ti.com/blogs_/b/powerhouse/posts/four-switch-buck-boost-layout-tip-no-3-separating-differential-sense-lines-from-power-planes

(+) Four-switch buck-boost layout tip No. 4: routing gate-drive and return paths - Power management - Technical articles - TI E2E support forums

Best regards,

 Stefan

Hi Stefan

Ok got it!

Stefan Schauer said:

it looks like the ground plane is split from left (controller) to power stage.
This will limit the grounding of the LM5176

Can you suggest ways to improve the Grounding connections??

Also please check the private chat as i have uploaded an updated board for review.

Hi Noel,

Stefan has forwarded me the layout files, as I will take over this thread.
I will review the updated board and get back to you within 1-2 days.

Thank you very much for your patience.

Best regards,
Niklas

Thank you so much Niklas! 

Ya i did not provide the updated files. The GND has since been connected.