TMS570LS3137: TMS570 Recommended Layout

Hello Joey,

We don't have PCB layout guidelines. Do you use 337-pin ZWT package or 144-pin PGE package? How many signals are used for your application? If all the signals are required, it is impossible to lay all the signals on one layer.

Please be aware of that each digital signal has a return signal through the group trace. The signal and its return trace should run together and be of equal length. It is better to have a separate ground layer.  

The CMOS circuits draw large currents at every transition, producing current spikes on the supply rails. The bypass or decoupling capacitors placed across the power pins and ground are used for such filtering. One capacitor on each power pin is recommended. The capacitor should be placed as close to the power pin as possible. For PGE package, the capacitors can be placed on top side or bottom side. For ZWT package, placing the capacitors on bottom side beneath the MCU is suggested.

Hi QJ, thanks for your feedback, apologies for the delayed response.

We are using the 337 ZWT package. Currently using ~20-25 analog ports, ~15 GPIO, some comm peripherals, ~16 HET inputs.. call it ~75 total signals or so.

We will plan to have dedicated power and ground layers. The bypass/decoupling caps would be as close to physically possible around the perimeter of the footprint to minimize distance as best we can on the primary side. Good to know regarding the recommendation for matching digital signal and return trace length. 

If we are able to place a minimum of one cap per power pin as close as possible (on primary/top side), and accommodate your other suggestions, do you believe that this configuration would incur significantly more risk than opening up the space below the BGA for a more traditional layout scheme in line with your general recommendation?

Thanks,

Joey

Hi QJ, is there a way for us to share a PM or email on this topic? I have a top side layout concept that reflects your recommendations as provided and would like to share some additional dialogue if possible without posting it to this forum.

Thanks,

Joey

Hi Joey,

It sounds like a good idea, but I haven't tried this way before.