Regarding Synchronization of the part. Is it NECESSARY to use an external clock, or can you simply connect the SYNC pin of one UCC12050 to the SYNC pin of another UCC12050? It is not clear that the use of an external clock is necessary for synchronization.
Thanks
Hi David,
My apologies for the lack of clarity in the UCC12050 data sheet. Thanks for bringing this to our attention and we will work to clarify the SYNC functional description. Yes it is necessary to use an external clock if you desire to SYNC two or more UCC12040/50 devices. If used, the SYNC pin is intended to be driven from an external 16 MHz digital clock. This is interesting because when an external SYNC signal is applied to the UCC12040/50, the internal spread spectrum modulation (SSM) is disabled. Some external clocking devices can have complex SSM algorithms which some advanced applications may want to use. The UCC12040/50 default internal SSM does a good job on its own of mitigating peak EMI and like all SSM techniques, the tradeoff is EMI reduction against low-frequency modulated output ripple.
From the UCC12050 data sheet, here is a good example of the impact that SSM has on low frequency modulated output ripple:
Regards,
Steve M
