hmc4069 PD output : +/-5V (pin NU, ND)， charge pump current is 10mA;
suppose vco tuning voltage is 0~15V.
As you see, they are not equal , and the latter（15V） is higher than former（5V)
As the datasheet recommemded , the loop filer is one op circuits , more likely a differential amp.
for AC signal , if the gain of amp >1, (for example , gain=3), the op can convert 5Vpp to 15Vpp.
but for pll, the input signal is a pulse signal.
my question is : can this circuit convert +/-5V pulse signal to a stable 15V tuning voltage ?
or it is more likely a integration circuits? once the tuning voltage is not reached, the pulse sigal will continue be produced.
and is there any other requirement for op, like VCC/VSS must be +/-15V likewise ?
Hi,
Yes it is possible to use the gain from the op amp in the active filter to tune over a wide vtune range such as 0 - 15V. So the loop filter here also acts as an amplifier. It also functions as an integrator…
Yes it is possible to use the gain from the op amp in the active filter to tune over a wide vtune range such as 0 - 15V. So the loop filter here also acts as an amplifier. It also functions as an integrator which takes the ND / NU pulses and converts to the tune voltage.
For designing the loop filter it is recommended to download free ADIsimPLL software, it has the HMC4069 included. Then you can add your model from the VCO's datasheet.
For more information on op amp choice with HMC series standalone PFDs please see here:
https://ez.analog.com/rf/f/q-a/91361/hmc439-loop-filter-op-amp-for-wide-bandwidth-pll