TRF3750 operation while ref_in signal off

Alber, Moon

Intellectual 720 points

Other Parts Discussed in Thread: LMK04808

Hello

I'm Alber as Arrow Korea FAE.

my customer asked the operation of TRF3750 when Ref_in signal is disappeared.(Ref_in signal off)

Ref_in Signal will be off, TRF3750 will be unlock status. at that time, what is the state of Charge Pump voltage?

zero volt? or fixed voltage?

in the past, customer tested and got the result that the voltage was swing in Charge pump voltage range randomly, like as below picture.

is this right operation?

over 7 years ago

0 RJ Hopper over 7 years ago

TI__Mastermind 18065 points

Yes, when the reference signal is lost the PLL will go out of lock. Without the reference the PLL control loop will be influenced by the noise within the system. The charge pump may rail to low or high or fluctuate randomly as you depict above.

--RJH

0 Alber, Moon over 7 years ago in reply to RJ Hopper

Intellectual 720 points

Hi, RJH

Thank you for your feedback.
Then, is there any way to go out fixed frequency when go out of lock? like as LMK04808's Hold Over Mode.....

0 RJ Hopper over 7 years ago in reply to Alber, Moon

TI__Mastermind 18065 points

No, the TRF3750 does not have such a feature. --RJH

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TRF3750 operation while ref_in signal off