Hello.I have this PLL loop filter around Tsa5511 and i have some questions.
What is the role of the circuit after uA741?
I also have an almost same circuit but with different values for the parts inside the red circle.
R26,R27=1K5
R28=680
C32=200nF
C33,C34=100nF
Which of the values perform better?
Thank you.
PLL Loop filter values
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fmmpastouni
- who u callin ne guy bruv
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PLL Loop filter values
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reverend
- tower block dreamin
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Re: PLL Loop filter values
The circuitously circled circuit is a Twin-T notch filter, presumably to notch out the loop filter reference frequency. Which works best depends on what the reference frequency is.
if it ain't broke, keep tweaking
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Krakatoa
- no manz can test innit
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Re: PLL Loop filter values
It is a notch filter. Presumably it's there to suppress residual reference frequency that may escape the loop filter itself. It helps to improve the spurious products nearest to the carrier frequency.
Just find out what's your reference frequency in your circuit and tune the notch circuit to filter it out.
There are design equations for the component values in typical electronics books, or maybe use a circuit simulator to try and tweak to taste.
Just find out what's your reference frequency in your circuit and tune the notch circuit to filter it out.
There are design equations for the component values in typical electronics books, or maybe use a circuit simulator to try and tweak to taste.
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fmmpastouni
- who u callin ne guy bruv
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Re: PLL Loop filter values
Hello.Thank you for answering.Things are more clear now.If i have understood well ,looking at the datasheet of TSA5511 the reference frequency derives from the frequency of the external crystal divided by 512 so for a crystal of 3.2MHZ the reference frequency is 6.25Khz.Is this the reference frequency you are talking about?
I run a simulation with LT spice and the frequency of the Tnotch i posted is around 6.4Khz while the frequency when using the othe values
(R26,R27=1K5
R28=680
C32=200nF
C33,C34=100nF)
is around 1Khz so these values dont do the job.
I run a simulation with LT spice and the frequency of the Tnotch i posted is around 6.4Khz while the frequency when using the othe values
(R26,R27=1K5
R28=680
C32=200nF
C33,C34=100nF)
is around 1Khz so these values dont do the job.
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fmmpastouni
- who u callin ne guy bruv
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Re: PLL Loop filter values
what type should pll loop filter capacitors be? multilayer or polyester film?
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jvok
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Re: PLL Loop filter values
Film will work fine, or C0G or NP0 ceramic. The ceramics will be cheaper