In my design I want to distribute an externally provided clock, but switch to a backup on-board clock (both are 10MHz) if the external clock fails. I'd like the mux to make this determination without external control, and I'd like the transition to be smooth (no missing or runt pulses). The ICS581-02 basically does this, but unfortunately it's obsolete.
Does TI offer anything with this functionality? CDCUN1208LP looked close, but it seems that it doesn't have a PLL inside, and therefore the output will stall during switchover.