Ground Plane Query for dual layer PCB

Thread Starter

SHARANYADAS

Joined Apr 13, 2017
60
Hi all

I am designing a wristwatch PCB in which there will be two seperate parts.The analog part consists of a Li-ion battery charger IIC,one Fuel gauge IC & some supporting discrete components(Diode,Mosfet,Resistor,Cpacitor etc).
The digital part consists of a MCU,RTC,Buzzer,Display & some supporting discrete components.By far,i've placed all the analog parts in the bottom player.The top layer is containing all the digital parts except the RTC chip due to lack of space in the top layer.
I will apply ground plane in the bottom layer.
Now,I have some queries :
1) Should I apply ground plane for the top layer also?If so,then should I use single/multiple via to connect it to bottom layer as I think If i use single via,then there would be voltage drop...
2) If i don't apply ground plane for the top layer,can I connect every individual grounds of digital part using vias to the bottom layer ground plane??

Please suggest!My ongoing PCB design is as follows:

1581067402188.png
 

dl324

Joined Mar 30, 2015
10,072
Here's the relevant portion of your picture:
1581091702291.png

Complete all of the routes before you start worrying about ground planes.
I will apply ground plane in the bottom layer.
Now,I have some queries :
1) Should I apply ground plane for the top layer also?If so,then should I use single/multiple via to connect it to bottom layer as I think If i use single via,then there would be voltage drop...
Ground planes can be used for shielding, but they aren't always needed.
2) If i don't apply ground plane for the top layer,can I connect every individual grounds of digital part using vias to the bottom layer ground plane??
It depends on the circuit. If you have high current in some of the connections, you'll set up a voltage gradient in ground. That can sometimes be a problem.
 

ronsimpson

Joined Oct 7, 2019
454
I would fill all the red side with ground. Area fill. This will pick up the connectors and switches. There is a through hole connector with pads not connected, connect these to ground. I think you can get ground to be all around the outside.

I might also fill the blue side with ground area fill. The top and bottom will connect through J1-ground pin and some VIAs.

It does not hurt to have more ground.
You do not have to connect traces to ground if you area fill over the parts. It will all happen.
You can turn on /off how you see area fills. Clear or Red, clear or blue.
Just save the board and play with grounds. See what happens.
 

Thread Starter

SHARANYADAS

Joined Apr 13, 2017
60
The max current flowing through the circuit on the load side when on battery(OLED on) is 17mA.The charge current is restricted to a max of around 48mA.
This is FYI...
 
Last edited:

eetech00

Joined Jun 8, 2013
1,843
Hi

I would:
1. route all power supply traces first.
2. Route critical signals.
3. Apply copper pour (GND) to both sides of PCB.
4. Clean up silkscreen (if any)

eT
 

Thread Starter

SHARANYADAS

Joined Apr 13, 2017
60
Ok,one of my query is resolved!The majority likes to apply copper pour on both sides.I will also do that!
Now,my next query is,How many vias should I use to connect both sides??Please mentioned proposed via size also....
 

Thread Starter

SHARANYADAS

Joined Apr 13, 2017
60
My pcb is nearly complegted.Only a mosfet & resistor will be placed on either side of the board for the Buzzer!Please take a look now.I have given several vias in places to lower the resistance!But,there is a main via connected to battery- on which all the ground planes are connected.Should I use another via near that to lower the resistance??please take a look!

Wristwatch1.png
 

Janis59

Joined Aug 21, 2017
1,063
Generally there are a number of well working methods. First is to use an another side as the pefect gnd. Simple, but problematic for any microprocessor for lack of place to realize the multitude of wire crossings. Then solution to push some wires toward zone of gnd plane and then back may demand a hundreds of vias, thus better be avoided. Second method is three-laye pcb but it is damn expensive and then any homebrewed pcb etching must be forgotten. Thus the third way is the copper hairbrush lines. Just some 5 mm x 0,5 mm current bar with a triangular feets, probably once a centimeter or once the inch. Those are going to gnd patches where concentrates the local multitudes of gnd pins, thus those busbars is just kind of third layer, however, most of cases it may be combined with identical bars for Vcc and then there is one beautiful thing one may solder the Vcc anti-ripple capacitors hanging free between both bars - it is rather good economy of space and as well gives a nice profesional made view, and gives a bar inductance hardly reduced. System proposed was extensively used by soviet military pcb~s in late 80 up to 90 and was extremely trustworthy.
 
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