USE DISCOUNT CODEEXPERT30TO SAVE $30 USD
I/O standard compatibility and other checks before PCB design
gyuunyuu1989 , 05-31-2023, 02:44 PM
When digital ICs interface with incompatible I/O standards, they will fail to communicate with each other. This means design failure.
If too high or too low power supply voltage is connected to an IC, it shall lead to eventual IC damage. This means (eventual) design failure.
When resistors have a too low power rating and they are driven by large current, they will burn out. This means design failure.
If differential signal are connected the wrong way around on the receiver side (i.e p and n are swapped), it shall lead to communication failure. This means (eventual) design failure.
Are these issues checked in Altium designer using design rules or they are at the mercy of the schematic designer to make sure that he has done the schematic design correctly? In other words, is there an automatic way to check these things in Altium designer or they can be checked only manually?
If too high or too low power supply voltage is connected to an IC, it shall lead to eventual IC damage. This means (eventual) design failure.
When resistors have a too low power rating and they are driven by large current, they will burn out. This means design failure.
If differential signal are connected the wrong way around on the receiver side (i.e p and n are swapped), it shall lead to communication failure. This means (eventual) design failure.
Are these issues checked in Altium designer using design rules or they are at the mercy of the schematic designer to make sure that he has done the schematic design correctly? In other words, is there an automatic way to check these things in Altium designer or they can be checked only manually?
qdrives , 05-31-2023, 05:46 PM
I will be very short: no they are not.
gyuunyuu1989 , 06-01-2023, 12:14 PM
So is there any other way that PCB designers check for this when there are dozens of ICs on the board that are connected together?
qdrives , 06-01-2023, 01:02 PM
First of all, then you select an IC, you select it for the voltage that your board is going to use.
If you have a 5V power MCU, do not use a 1.2V logic device. The other way around will also not work.
For every resistor you place in your schematic, you check the power that needs to be dissipated, the maximum voltage and current over and through it.
Whenever you are naming and numbering things, do a quick check after you placed / assigned them.
Yes, things can go wrong. But of every component you place, >99% can be done correctly if you apply these simple rules.
If you have a 5V power MCU, do not use a 1.2V logic device. The other way around will also not work.
For every resistor you place in your schematic, you check the power that needs to be dissipated, the maximum voltage and current over and through it.
Whenever you are naming and numbering things, do a quick check after you placed / assigned them.
Yes, things can go wrong. But of every component you place, >99% can be done correctly if you apply these simple rules.
robertferanec , 06-05-2023, 04:17 AM
There are some ways to check schematic - it is called ERC, but do not expect miracles. It's mostly simple input / output checking. If you really would like to check schematic properly, it needs to be done by an engineer.
This is how I check schematic: https://youtu.be/CDAuCchchtI
This is how I check schematic: https://youtu.be/CDAuCchchtI
gyuunyuu1989 , 06-05-2023, 06:21 PM
I am an electronic engineer myself actually 
The thing is, when we have a large schematic, it is possible to forget about checking the I/O voltage compatibility with other components. I am saying this since in the past, I have seen people make mistakes where e.g a 3.3V clock was connected to a 1.8V I/O buffer or the CMOS-TTL levels were mixed in such a way that communication could work in one direction but not the other. Sometimes fixing such simple mistake can be quite very expensive.
The thing is, when we have a large schematic, it is possible to forget about checking the I/O voltage compatibility with other components. I am saying this since in the past, I have seen people make mistakes where e.g a 3.3V clock was connected to a 1.8V I/O buffer or the CMOS-TTL levels were mixed in such a way that communication could work in one direction but not the other. Sometimes fixing such simple mistake can be quite very expensive.
qdrives , 06-06-2023, 02:17 PM
One of the ways I check the schematic is to set the net colors (View / Set Net colors / ...)
The net I am checking gets a color, ie orange. Either use the navigator or just go through all sheets to check the connections (this includes voltage levels if needed).
Once all connections are checked, give the net the Ok color i.e. green.
When all nets in the design are green, you have checked them all, so it is easy to verify if you are done.
Do not forget to save the project if you need to continue after closing Altium.
The net I am checking gets a color, ie orange. Either use the navigator or just go through all sheets to check the connections (this includes voltage levels if needed).
Once all connections are checked, give the net the Ok color i.e. green.
When all nets in the design are green, you have checked them all, so it is easy to verify if you are done.
Do not forget to save the project if you need to continue after closing Altium.
robertferanec , 06-13-2023, 12:23 AM
The thing is, when we have a large schematic, it is possible to forget about checking the I/O voltage compatibility with other components ...
here you can find a pdf I created a long time ago, it may help: https://welldoneblog.fedevel.com/201...ing-procedure/
Use our interactive Discord forum to reply or ask new questions.