high frequency pcb designing

[gehan_s]

Hi all,

I have to do routing between a pic micro controller and an ade7758 energy measuring chip. They communicate using SPI and the master clock is 1MHz. What kind of precautions do I have to take ?

Please help me to decide max track length, width, termination (Using pull down resistors or caps) etc

These two chips are optically isolated using a 6n137 opto isolator. Can it handle such high frequency communication ? (It says 10MBit/s but does anyone have experience with this IC?)

Thanks in advance !!!!!!!!!!!!!!!

 

[Mike odom]

1 MHz clock speeds are not that uncommon in microcontroller pcb design. As always, use max trace width/spacing available, and shortest run length possible. If the opto is rated for 10Mb/sec, then it should be fine. Keep spacing to ground planes at a maximum, 25+ mils should be alright. Also, try to keep a plane on the opposite side from the runs, and split it under the opto, keeping the input ground plane away from the output ground plane and separate. Do not run input lines over the output plane and vice versa. The data sheet for the ade7758 should tell you if you need line terminations or not. I would think not, but I guess it depends on your layout. I've done motherboards up to and including 100MHz.