LMK04816: Generating 125 MHz and 150 MHz from the same LMK04816 part.

Doug Bailey

Part Number: LMK04816
Other Parts Discussed in Thread: LMK04805, LMK04808

I am trying to derive a 150 MHz and 125 MHz signal from a LMK04816 that is input with a 50 MHz reference clock.

When I run TICs Pro, it indicates that the PLL2 output is bounded from between 2370 MHz and 2600 MHz. Since I cannot find a common multiple for 125MHz and 150 MHz in the 2370-2600 range, I assume that I cannot derive these two clocks on the same part.

Am I wrong? How would I do this?

Regards,
Doug Bailey

over 5 years ago

0 Derek Payne over 5 years ago

TI__Mastermind 30770 points

Hi Doug,

The least common multiple of 150 MHz and 125 MHz is 750 MHz, so you will need a multiple of 750 MHz to generate both frequencies. There is no multiple of 750 MHz in the 2370-2600 range. So your assumption is correct, the VCO range on the LMK04816 cannot support simultaneously generating 125 MHz and 150 MHz.

The LMK04805 (2148 to 2370) and LMK04808 (2750 to 3072) both have VCO ranges which support simultaneous generation of 125 MHz and 150 MHz. The LMK0480x family is P2P compatible with the LMK04816 in most circumstances, though there are minor differences (LMK0480x has two clock inputs, and trades CLKin2 for a second OSCout). I recommend looking at the LMK04805 or the LMK04808 instead.

Regards,

Clock & timing

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LMK04816: Generating 125 MHz and 150 MHz from the same LMK04816 part.