DC-DC buck layout

[Pranav.Dosajh]

Hi

I am having difficulty in routing high voltage to low voltage buck converters on embedded automotive boards (specifically 24V to 5V --3A converters) I am using a 6 layer stackup with TOP--> GROUND PLANE--> SIGNAL1 --->SIGNAL 2 --->POWER PLANE----> BOTTOM. most of these buck converters have reference layout for (2 Layer or 4 layer ) and many times these converters end up failing due to ground loops,These converters work very good if i use them as a standalone PCB and connect to my embedded board via connectors. I need to use the converter on the same board and require some help on what is to be taken care when routing specially ground since it is a non isolated buck converter it shares a common ground.

[robertferanec]

What is the chip?

PS: Use a chip which has a reference board (so you can do layout the same/similar way) and PCB layout/placement requirements described in datasheet. Requirements are usually very similar e.g. keep the high current and switching tracks short, wide, keep critical components close and on one layer, you may want to use shielded inductor etc.

You can read for example this ISL6236A datasheet (Page 35): https://www.renesas.com/eu/en/www/do...t/isl6236a.pdf
And have a look at reference layout here: https://www.renesas.com/jp/ja/www/doc/guide/an1272.pdf

[Pranav.Dosajh]

Hello Robert

Thanks for the reference designs will surely look into it.
I am using TI's TPS54340DDAR, followed the reference layout of the IC but it gets hot at no load and stops working after 1 or two hours of working. I am not able to figure out the reasons for its unstable behavior. There is some design error only because this chip works in standalone pcb.

[Lakshmi]

1) Check for the continuity/ short. (usually capacitors)
2) Is 3A is your continuous Load current Or peak(max) current?
3)Looking at your stack-up I'd assume all the IC which requires12V,5V are on the top layer, If not I'd recommend using S1, GND,Power&Signal, Signal, GND, Signal Layer stack-up. (Make sure you've reference plane for each Signal and Power Layers)
4) TI has an e2e forum where you can post your queries and also can get your design reviewed before Manufacturing.
5) Usually, It's not a good idea to use NRND(not recommended for new design) part number.

[Pranav.Dosajh]

1) Checked the continuity no problems in that
2) 3A is the peak load, The IC never touches the peak load, In fact the current draw is only about 12mA at minimum load.
3) I have placed all the IC's on Top Layer as per my stackup
4) I shared my problem on e2e forum but did not got any solution although i got a reference design
5) TI suggested a drop replacement for the part so I designed with the older part which I had

[mir0mik]

Hi

I am having difficulty in routing high voltage to low voltage buck converters on embedded automotive boards (specifically 24V to 5V --3A converters) I am using a 6 layer stackup with TOP--> GROUND PLANE--> SIGNAL1 --->SIGNAL 2 --->POWER PLANE----> BOTTOM. most of these buck converters have reference layout for (2 Layer or 4 layer ) and many times these converters end up failing due to ground loops,These converters work very good if i use them as a standalone PCB and connect to my embedded board via connectors. I need to use the converter on the same board and require some help on what is to be taken care when routing specially ground since it is a non isolated buck converter it shares a common ground.

You can change the stack-up locally for the buck if you cut it out in Z axis...
Also I suppose you should be able to route it on one layer + another for ground (not that the vias are only for input, output, ground and ther rest is just for test points on the bottom side) and still have minimal loops...

[robertferanec]

I am using TI's TPS54340DDAR, followed the reference layout of the IC but it gets hot at no load and stops working after 1 or two hours of working.

- this looks to me more like design problem ... something connected wrong way.