I am working on a new PCB design that is supposed to deliver power to another PCB I call this with a dummy name “Board A”. The Board A already exist in the lab. There are two identical circuits on the Board A. Each require 1.0 V DC and 2 A. This means in total the Board A needs 4 A current at 1.0 V.
The new PCB design I am working is to deliver power to that Board A.
As the main power supply we have 9 V to 12 V available at the input. I will be using DC-DC converters on the new PCB to convert the input voltage to 1.0 V.
We already have decided that we need two identical DC-DC converters on the new PCB design. Each DC-DC converter will deliver 1.0 V DC and 2 A that is sufficient for half part of Board A.
My question is on designing power and ground planes for DC-DC converters.
Should I have one power and one ground plane for both DC-DC converters ?
Or should I have one power and one ground plane for each DC-DC converter ?
Why are you using two converters? Is it just hard to get a single converter that puts out 4 amps, or are you trying to protect the two circuit copies from each other?
Are you trying to get large planes to spread the heat from a pair of circuits that will often run at different times, or are you running two sensors and trying very hard to avoid letting them couple?
A little background. In fact there are two identical circuits on the Board A. Each circuit require 1.0 V DC and 2 A current. In total the Board A needs 4 A current at 1.0 V. We are using two DC-DC converters on the new PCB design. Each DC-DC converter will deliver 1.0 V DC and 2 A current that is sufficient for half part of Board A.
I understand that one can find a DC-DC converter that deliver 4A output current but the selection of DC-DC converters is already done and for some reasons we need to use two DC-DC converters. Each DC-DC converter will power up half of the BoardA.
We actually need to protect at least half of the circuits on the BoardA. In case of one DC-DC converter failure, or if one DC-DC converter does not turn on at the same time, then the other DC-DC converter will still be able to deliver power to half of the BoardA. This way each DC-DC converter will work independently and deliver power to half of the BoardA.
I think we should not combine the output of both DC-DC converters and connect them to a single wire or a single plane. In addition, we also need to keep their return paths separate. This means there will be four wire delivering power to the BoardA. One pair from each DC-DC converter. Is that right approach ?
As noted, the first thing you want to know is the goal of your design. Is it redundancy, cost, thermal management, etc. My very first thought was “Why two converters? I’m sure it could be done in one chip.” So, not knowing the end goal I can’t add a lot to what’s been posted but if it’s for redundancy purposes I think I would keep grounds separate along with power planes, return paths, and anything else you can isolate.
DC-DC converters are very important for any PCBs and can be a source of EMI/EMC as you may know. From that perspective, its important to keep one solid ground plane.
I dont have much details about why do you need two separate converters, but if its redundancy then in theory you dont have to have one common power plane. You can treat them as seperate power supplies and have two separate power plane.
Does Board A use separate GND references per circuit? If so, then the PWR supplies should also maybe be configured the same. If the GNDs are common, then the PWR GNDs can be common so long as the connections can support the total current. It sounds like the 1V PWR should be separate - reason being that if one load fails, you do not want it taking down both power sources.
Also, 1V source supplies generally need to support very tight tolerances to stay within the load requireements. You do not want to create any unintended situations that might affect independent regulation.
One last thought - Tying multiple power supply outputs together is generally a bad idea since one supply may attempt to react quicker than the other and if that happens, you might find one supply being overloaded while the other one coasts.
We are not going to combine the PWR and GND of both power supplies. Each power supply will just power up half of the load on BoardA, not full. If one power supply is down or broken then we only lose the half of the BoardA. We will keep PWR and GND of each power supply as separate planes on BoardA.