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Dear Members!
I would like to ask your opinion about impedance control on PCBs. I am hardware developer and I design high speed PCBs at a big company where we have more high speed interfaces on the boards, like oLDI, HDMI, FPD link, APIX, LPDDR4, MIPI CSI etc. Until now we did not use impedance control on our PCB-s. Our maximum datarate is currently 3Gbit/s.
I think that impedance control is very important but most of my colleagues say that until now there were no problems then why should we use...
What is the border where we should begin to use impedance controlled pcb-s? Do you know with what kind of tolerance pcb manufacturers work with and without impedance control?
I know that these problems could occur:
- video distortions (pixel errors and synchronization gaps)
-- data interfaces will have transfer gaps, bit errors
-- DRAM errors
-- significant increased EMC (impedance jump -> causes reflections -> causes emissions)
-- Impedance jump from Chip-out to trace and on Board-to-Board routings
The problem is that I have never seen such problems in our projects (we sell from one product 300-400 thousand pieces / year) and I do not know how I could prove that without impedance control we are bad.
And we use higher and higher datarates. For example we use in our new projects LPDDR4 instead of DDR3, where we have instead of 533MHz a clock frequency of 1600 MHz, so rise and fall times are also much shorter. That's why I am thinking that maybe the time has come to use impedance control
What do you think about this topic?
Thank you for your answers in advance!
best regards,
Andras
I would like to ask your opinion about impedance control on PCBs. I am hardware developer and I design high speed PCBs at a big company where we have more high speed interfaces on the boards, like oLDI, HDMI, FPD link, APIX, LPDDR4, MIPI CSI etc. Until now we did not use impedance control on our PCB-s. Our maximum datarate is currently 3Gbit/s.
I think that impedance control is very important but most of my colleagues say that until now there were no problems then why should we use...
What is the border where we should begin to use impedance controlled pcb-s? Do you know with what kind of tolerance pcb manufacturers work with and without impedance control?
I know that these problems could occur:
- video distortions (pixel errors and synchronization gaps)
-- data interfaces will have transfer gaps, bit errors
-- DRAM errors
-- significant increased EMC (impedance jump -> causes reflections -> causes emissions)
-- Impedance jump from Chip-out to trace and on Board-to-Board routings
The problem is that I have never seen such problems in our projects (we sell from one product 300-400 thousand pieces / year) and I do not know how I could prove that without impedance control we are bad.
And we use higher and higher datarates. For example we use in our new projects LPDDR4 instead of DDR3, where we have instead of 533MHz a clock frequency of 1600 MHz, so rise and fall times are also much shorter. That's why I am thinking that maybe the time has come to use impedance control
What do you think about this topic?
Thank you for your answers in advance!
best regards,
Andras
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