At page 3 of LMX2485E PLL datasheet:
“…The voltage at all the power supply pins of VddRF1, VddRF2,VddRF3, VddRF4, VddRF5, VddIF1 and VddIF2 must be the same. VCC will be used to refer to the voltage at these pins and…”
and the normal operation condition is 3.0Volts.
My question is: In the future, WIll be any planified improvement of this component to increase the RF charge pump VCC to 5.0Volts with a VCC pin dedicated?
Another PLLs from your competitors like ADF4252 from Analog Devices haves that funcionality that improves phase noise.
Due to process limitations, the max voltage is 3.6 volts. At this time, to use this part with a 5 volt VCO, you would need an active filter with an op-amp.
Another workaround is that you could just use a device with an integrated VCO that eliminates this issue of tuning voltage.
But if you have a 5 volt external VCO that you really want to use and are unwilling to use an op-amp, we have no solution today.
We are discussing this kind of thing in the future and have means to do this, but this is not certain now and even if it was, I can not discuss in an open forum.
For this application, what frequency is your VCO running at and are you really needing a fractional PLL or would an integer PLL be sufficient?
Thanks Dean for your information.
With regards to your question, we have the TRF3765 (http://www.ti.com/product/trf3765?DCMP=analog_signalchain_mr&HQS=trf3765-pr), powered at 3.3V but it has the VCC_TK pin than can be powered up to 5.5V increasing device performance.
In the other hand, if power comsumption is not a concern, there are some other parts with supply rails up to 5V or 5.25V.
Please, feel free to contact me directly if you have further questions!.
BR, Jose Luis.
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