LMK03318: no output

user4125429

Part Number: LMK03318

HI,

I am using LMK03318 now, but there is no output.

I use an 10MHz oscillator as secondary reference input， doubler enable， M-divider set /2 ，VCO at 5000MHz ，and VCO out at 1000MHz, C2 is 33nF.

I need some 40MHz CMOS output so i set output-divider as 25.

But there is no output.

When i set clock source at secondary reference input, for example channel 5, i can see 10MHz output.

I think this problem maybe the wrong set of R2 R3 C1 C3，but not sure.

help me please.

Best regards!

Leon

over 7 years ago

0 Alan O over 7 years ago

TI__Mastermind 32575 points

Check the GPIO0 pin is pulled high to de-assert the output divider synchronization.

Try toggling RESETN_SW bit low then high to re-initialize the device and trigger VCO calibration after programming the registers.

See this tutorial on the LMK033x8 loop filter design and simulation tool.
training.ti.com/lmk03328-webench-clock-architect-design-tutorial

Alan

0 user4125429 over 7 years ago in reply to Alan O

Prodigy 70 points

Thank you so much! It works!
But now I have another problem, when using an 10MHz single-end sinusoidal signal (Vpp @ 800mv, Vdc @ 1V) as primary reference input, and there is no output.
I just change R50 from 0x83 to 0x82, is there any other register i have to change?

0 Alan O over 7 years ago in reply to user4125429

TI__Mastermind 32575 points

The swing is too small for S-E/LVCMOS input buffer mode. Try changing to DIFF input mode which allow smaller input swing.

Alan

0 user4125429 over 7 years ago in reply to Alan O

Prodigy 70 points

For some reason i must use S-E primary input reference, so I try 1.6V Vpp@1V Vdc, but it still no work.
And in datasheet it says that, Vin high voltage is >1.4V, and low voltage is <0.5V, sheet8.9, page 10. I think my input signal is match the voltage level.
So is there any other reason can cause this problem?

0 user4125429 over 7 years ago in reply to user4125429

Prodigy 70 points

And also when i set clock source at primary reference input, for example channel 5, i cannot see any output.

0 Alan O over 7 years ago in reply to user4125429

TI__Mastermind 32575 points

The reference detector has a more stringent requirement than the Vih/Vil specs. Try to set Reference Detector = Disabled, and check if the PLL locks and if PRIREF can be seen on OUT5. If it works, that means the Reference Detector was previously disqualifying the input due to not meeting it's input threshold criteria.

Alan

0 user4125429 over 7 years ago in reply to Alan O

Prodigy 70 points

OK now!!!

Thank you so much!!!

It works when i set reference detector disable.

Thanks again.

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LMK03318: no output