Part Number: LMX2571
Please advise me on my questions bellow.
I wan to implement FM modulator using say LMH2571.
According to E2E article, there are two ways, analog and digital method.
Q1. Are there any TI designs which proof either or both ways?
Q2. In analog implementation, you can realize FM modulation tweaking VCO control voltage.
Can you show me an example schematic which can tweak VCO control voltage?
I concern that injecting audio signal to the loop filter may case substantial charge pomp
current leakage casing the PLL out of lock.
Q3. The method, tweaking VCO control voltage, require low loop band width.
If you need to support as low as say 100 Hz, PLL loop band width should to be
lower than 100Hz.
Can LMX2571 maintain good phase noise, or implement such low loop band width?
Can you provide me any update.
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In reply to user4779049:
Q1. No, we don't have TIDesign in this regard
Q2. Although it is possible, we do not recommend modulate the internal VCO.
Q3. As long as the phase margin is enough, the loop bandwidth could be smaller than 100Hz.
In reply to Noel Fung:
Thank you for the answers.
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