What's VCO free-running meaning ?

[ilovebow]

Anyone give some explaination.

Thanks .

[khouly]

this is the frequency , which will be out of the VCO without applying the control voltage ,


khouly

[samchieh]

It's the frequency of the VCO outside of a PLL, yes I agree, it is the oscillation frequency when there is not a control voltage.

[E-design]

VCO can have a control voltage and still be un-locked. Steering a VCO with a voltage from say a variable bench PSU does not make it locked. I would say free-running is anything outside the closed PLL loop. A loop can be opened and the control voltage can go either pin high or low, depending on the design.

Wording from a patent document

BACKGROUND OF THE INVENTION

Electronic devices such as RF (Radio Frequency) receivers, transmitters and various other devices include a VCO operating within a PLL (Phase Locked Loop) to maintain a desired oscillation frequency.

It is conventional practice to tune a VCO to a particular initial frequency before it leaves its factory. This is typically accomplished by using factory equipment to measure the frequency of the VCO while it is free-running (i.e., the PLL is opened),

[ilovebow]

Thank you everyone

[Yahia Muhammad]

it's the VCO running stand alone ( not in closed loop with a PLL )

[trashbox]

The VCO is not in PLL closed loop, I think.

[jecyhale]

Anyone give some explaination.

Thanks .

it means VCO runs without PLL.