Arduino Mega schematic

Hi, I'm drawing Arduino Mega schematic for my project and I have some question that I appreciate your help by answering them.

1- In the attached pic. the parts in the blue circle, (L1, F1, Z1, Z2) can I ignore them in my circuit? If not, can I replace them with other values (please mention the possible value), because these parts are not available in the SMT service of my supplier.

2- In the yellow circle. When do I have to connect both grounds and when I should not?

3- Why I have two ICSP in Arduino Mega (one for ATMega2560 chip and one for ATMEGA16U2-MU)? and to which one I have to use to burn the bootloader?

Thanks

2- In the yellow circle. When do I have to connect both grounds and when I should not?

Do a search for "arduino mega ugnd" for many discussions on that.

3- Why I have two ICSP in Arduino Mega (one for ATMega2560 chip and one for ATMEGA16U2-MU)? and to which one I have to use to burn the bootloader?

One is for programming and bootloading the 2560 chip and the other for the 16U2 USB to serial converter. Bootload the 2560 with the 6 pin header next to the 2560 chip. See the image.

Thank you for your answer.

So the first question is remaining. Can I remove the mentioned components from the circuit?

F1, that protects your PC in case of a 5V overcurrent situation on the board.
Look at your source for PTC Resettable Polyfuse, see if you can find a low resistance part to use.

Z1 and Z2 are Transorbs.

These come into effect when there is static discharge on the connector.

Static would be shunted to earth.

If there is no concern about ‘static’ these components are not necessary.

The earth ground is probably already connected to 0v back at the host usb connector.

Thank you guys for your answers, I have one last question.
I asked if I can ignore them because I didn't find exact same parts, so can you advice if I can replace them with the following parts.

This part
https://lcsc.com/product-detail/Ferrite-Beads_Murata-Electronics_BLM15PD300SN1D_Murata-Electronics-BLM15PD300SN1D_C85822.html
Instead of this part
https://www.onlinecomponents.com/en/bourns/mh2029300y-10752288.html

And this part
https://lcsc.com/product-detail/Surface-Mount-Fuses_0-5A-60V-Self-healing-fuse_C178319.html
Instead of this part
https://lcsc.com/product-detail/Surface-Mount-Fuses_BOURNS_MF-MSMF050-2_0-5A-15V-Self-healing-fuse_C17313.html

And is there any replacement exists here
https://jlcpcb.com/parts
Of this part
https://www.digikey.com/en/products/detail/bourns-inc/CG0603MLC-05E/2538084

Thank you again and appreciate any help

Regarding Z1 and Z2, while it is correct you don't need them if you will not have any ESD into your USB input. The fact is it is very likely you will have ESD which will blow out your processor.

While there are a number of ways to suppress ESD I would look for a trv diode with a standoff voltage of 5V.
If you can find a bidirectional trv you can use one to replace the Z1 (and another for Z2)
If you can only find unidirectional trv's you will need two to replace Z1 and another 2 for Z2.

Question:
Are you attempting to make your own PCB? If so you need to look very closely at the current production mega layout. Especially at the input power and crystal. Physical location on the PCB is important for this type of circult.

Good luck.
John

This part
Murata Electronics|Murata Electronics BLM15PD300SN1D|Ferrite Beads|LCSC
Instead of this part

No that is a totally different type of component. The Transorb protects against specific over voltage, so in this case anything over 5V gets absorbed because the Transorb's resistance changes sharply. You could achieve a similar, but not as good effect, using a series resistor and a 4.2 to 4.7V zener diode. The bigger the resistor the more protection but at the expense of slowing the signal edges.

The part in that link is just a ferrite bead and just slows down current rise times, there is no voltage protection, other than that which results from a slower rise.

When posting links please do not click on the box that prevents a new tab opening, it makes it hard to follow things.

Grumpy_Mike:
When posting links please do not click on the box that prevents a new tab opening, it makes it hard to follow things.

Then we agree. :grinning: I have been saying the same. I would/ will say it more regularly if/ when I am no longer constrained by this laptop on a hospital bedside table!

One tends to wonder why people click it, but it seems that the fact that it is offered at all makes it appear that it may actually be some sort of “good thing”, is somehow desirable! :roll_eyes:

What not infrequently happens however, is that when you back out of the link using the same tab, you have for one reason or another in the browser operation, lost the previous place and context. Of course I always have the “Open in New Tab” option for links.

Hi,
Is there a reason you are making a new PCB?

If you are after a smaller footprint then google Arduino Mega 2560 PRO MINI

s-l1600.jpg
If it is to be part of an embedded PCB, you place header sockets on your PCB for the above assembly to plug into.
90% of your work is done, bootloader already loaded.

Tom... :slight_smile:
PS, I do this with 328 based projects using a Nano.

s-l1600.jpg

Sorry guys, I don't know why it is the second time my reply is being posted partially! I have updated my last reply. Please check it again

This not generating new tabs behaviour is on the increase, especially people new to the forum.
I often find myself clicking on a link to check something after I have composed most of my reply. Then the back button some times loses the post but other times doesn’t.

when I am no longer constrained by this laptop on a hospital bedside table

Hope you are out of there soon.

TomGeorge:
Hi,
Is there a reason you are making a new PCB?

I'm creating my own PCB to add other drivers and modules in the same PCB board. I have already done some similar projects using ATMEGA328P but it is much more easier than using ATMega2560.

hsalame:
Sorry guys, I don't know why it is the second time my reply is being posted partially! I have updated my last reply. Please check it again

Please do not update a post after it has been replied to, always add a new post so that the flow of the thread is not misleading and confusing.

I'm creating my own PCB to add other drivers and modules in the same PCB board. I have already done some similar projects using ATMEGA328P but it is much more easier than using ATMega2560.

Well you still can, but save yourself a lot of work and firmware uploading and debugging by using a readily available assembly.
Tom... :slight_smile:

TomGeorge:
Please do not update a post after it has been replied to, always add a new post so that the flow of the thread is not misleading and confusing.

Ok.

TomGeorge:
Well you still can, but save yourself a lot of work and firmware uploading and debugging by using a readily available assembly.

I don't want to go that way. I have already finished the schematic and ready but just have this little question, about replacing (L1, F1, Z1, Z2).

Grumpy_Mike:
This not generating new tabs behaviour is on the increase, especially people new to the forum.
I often find myself clicking on a link to check something after I have composed most of my reply. Then the back button some times loses the post but other times doesn’t.

Now that as you mention it, is a seriously frustrating aspect to to the problem as I have also found. :roll_eyes:

There are better components available now for the USB input protection circuit. You should have a shop around instead of copying the Mega.

I didn't get answer for this question, could anyone help me?

Is there any replacement exists here
https://jlcpcb.com/parts

For this part
https://www.digikey.com/en/products/detail/bourns-inc/CG0603MLC-05E/2538084
Data Sheet

Hi,
Did you have a live chat with JLCPCB, on the library page?

How many PCBs are you aiming to build?
If this is the prototype then add the varistors yourself.

SMD is not hard to solder, especially if only a few and you make sure you have the space to get the soldering iron tip in.

Tom... :slight_smile:

TomGeorge:
Did you have a live chat with JLCPCB, on the library page?

How many PCBs are you aiming to build?
If this is the prototype then add the varistors yourself.

Hi,
I asked them about other parts but they don't support in the pcb design and picking parts.
Actually yes it is a prototype, but I need it to be soldered with their service because if everything is fine, I will order too many PCBs