How to power 3.3V peripherals of C6457 correctly if its not used?

Chad,

Thanks for answer.

Really, 6.4.2 of the C6457 HW Design Guidelines describe this case, but please correct me if I mistakes when read it:

1. EVERY LVCMOS_3.3V I/O pins (HPI ~42pins + EMIFA~100pins + UTOTIA~35pins = totally ~180 pins ) should pulled up undependentely to  1.8V power line;

2. All DVDD33 pins  should be left unconnected

I didn't count the actual IO pins, but yes that's the correct interpretation.

Best Regards,

Chad

I suppose that's a matter of interpretation.  You eliminate the 3.3V supply and power plane altogether. And you're not routing out the 3.3V IO's but can directly connect them to the 1.8V plane. It's no more complicated than requiring them to be tied to ground which has been done on other devices and the only way to be less complicated would be leaving them floating which we are not recommending.

Best Regards,

Chad

Chad,

Thanks for helping me to find the best way for my device.

But detailed method to "tie" unused 3.3V periph to 1.8 power rail is still unclear.

Chad Courtney said:

you're not routing out the 3.3V IO's but can directly connect them to the 1.8V plane

If so, there are some PCB simplification, but SPRAAV7B said: "the 3.3-V power supply can be omitted if the 3.3-V IOs are pulled up to the DVDD 1.8-V power rail". Typically docs like SPRAAV7B explicitly said "to tie directly" if it's true, but there wrote "pulled up", that typically implicit connection through ~some kOmh resistor (per 1 pin).

BR&Thanks,

Serge

Chad,

Thanks for help.

P.S. For my board I've decided to power DVDD33 by native 3.3V without any tricks (fortunately I have already 3.3V rail).

BR&Thanks,

Serge