Author Topic: Ground pour in double output buck converter - one pcb  (Read 643 times)

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Offline SombiefogTopic starter

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Ground pour in double output buck converter - one pcb
« on: July 15, 2019, 07:51:35 am »
Hi!

So im making a dc/dc buckconverter using TI's LM5088 and LM5117. These are going to make two different outputs and have two seperate inputs. Im going to use a microcontroller to switch the relays from the input on/off which then gets fed into the two different circuits. And i've come over a little question which i thought somone here might be able to answer. Right now im having the ground pour be seperate for the two different circuits of the LM5088 and LM5117 - BUT they still grounded together inside my AC/DC converter (Im guessing here - should be tought right? :D).

So my question is - is it ok to use the same groundplane for the two different outputcircuits.

For some reason i thought it would mess with the fidelity of the output if i leave two different outputs with the same groundplane.

(The outputs are 4,5V 15A - 12V 7A.
Input is 48V 10A)

Thanks for any reply  :-+

 

Offline capt bullshot

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Re: Ground pour in double output buck converter - one pcb
« Reply #1 on: July 15, 2019, 08:22:23 am »
If their output is at the same GND (as you descibe), just use one ground plane for everything.
Regulation will be referenced to that GND, which should be the same for both. If you split the planes (and don't have a connection on your board), the wire resistance from the 48V will induce some (probably small) difference to these two GNDs, if your converters feed two isolated circuits, this wouldn't matter, but if your converters feed two voltages into a circuit with common GND, you don't want this difference. Additionally, you'd create a GND loop then, this isn't a good idea EMC wise.
Safety devices hinder evolution
 
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Offline SombiefogTopic starter

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Re: Ground pour in double output buck converter - one pcb
« Reply #2 on: July 15, 2019, 08:27:23 am »
Great!

Il merge the grounds  :-+
 


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