MC145151/2 p2 calculation dip swich vs xtal divader

[rigmo]

Hi Guys Boys
Im 41 old an I stop play with this since 1997... but few month before I starting play again with my old FM pirate station.. I newer know how its PLL works indeed... i know now...
My biggest problem is I do not know how to calculate steps with different xtal and get formula to adjust dip switch 14...
can you help me to understand in few examples..

(Pleas can you help me to understood this IC to get almost any combination for my play.
I can not see haw calculate with this https://www.fpqrp.org/pigg20/SPECS/pll-des1.gif
And haw calculation goes if i change crustal 5.120mHz 3.2mHz...
step 25 50 100kHz

Sorry ... Yes PLUS and if I use difrent diveder... /8 /10 / 64.......
Can you show me some example.. )

Thank you in Advance
Best Regards

 

[BigBoss]

But this is Reference Divider truth table.
You should calculate the Xtal frequency by backward.I mean, if the Step Frequency 25 kHz so this is also Channel Step, you should select a proper Xtal by Dividing Ratio..
For instance, let say Step Frequency is 75 kHz, you assign a divider ratio 256 to the Reference Divider.In this case Xtal frequency will be 256*75kHz=1.792 MHz etc..
You can play with either step frequency ( Reference Divider Output ) or Xtal frequency.

 

[betwixt]

I'll try to keep it simple:

The device is two frequency dividers and a phase comparator. The comparator circuit produces a voltage proportional to the difference in the frequencies LEAVING the two dividers.

The two dividers are essentially the same except for how configurable they are.

Divider 1 is driven from a crystal oscillator, this is what gives it the overall stability. Whatever crystal frequency you choose, it can be divided by 8, 128, 256, 512, 1024, 2048, 2410 or 8192 by connecting RA0, RA1 and RA2 as appropriate to ground. The result of the crystal frequency divided by the selected number is a fixed reference frequency and will be the same as the frequency difference between one 'step' and the next.

Divider 2 is driven from an external VFO source, the frequency it sees is whatever frequency the VFO runs at. The 'N' pins select a number which is used to divide that frequency by the selected 'N' value. So 'VFO/N' comes out of the divider, it is directly available at the 'fV' pin on the IC.

So you have two signals leaving the dividers, one is fixed by the crystal and 'RA' divisor, the other is the VFO frequency divided by 'N'. The difference between them is produced by comparing them in a phase detector circuit. It gives you the error between the two signal frequencies which you can then use to tune the VFO to make the error zero. When (if) it detects zero error it means (Crystal / RA value) = (VFO / N) and it lets you know by making the LD pin (Lock Detected) pin high.

If you change the 'N' value, the divided VFO frequency will no longer match the divided crystal frequency so the phase detector will again produce an error voltage which you use to tune the VFO so it brings the frequencies together again.

Hope that makes sense!

Brian.

 

[rigmo]

Thank You guys pleas do not close this post. I need time to see. I make few more questions.
Thank You in advance
Best Regards

p.s.

22/5000
here we have experts for VCO ? I heave electric schematic and I need to se its good or need some changes.. ? I planed meke in smd ( do i need open new post) ?

 

[KlausST]

Hi,

I planed meke in smd ( do i need open new post) ?

your headline is: "MC145151/2 p2 calculation dip swich vs xtal divader "

If you want to discuss other things than mentioned in this headline, then open a new thread.

I heave electric schematic and I need to se its good or need some changes..

My advice: keep on the datasheet, application notes and other informations provided by the manufacturer

Klaus

 

[rigmo]

Tnx, its good to know And understood to, now.
how to get dip switch 1-14... how to calculate this? If I know for example:

step 25khz (2048*25=5.120Mhz) RAO RA1 RA2 its 101 ( its 1 open ( not connected on the ground) or 5V supply )? = 0 its on the ground in this example.. ?

this MC145151 heave potential.. its old but... I do not know anything about pic-s... Have anyone ever written a PIC program so that they could manage with DIP and RA?

- - - Updated - - -

I'll try to keep it simple:

The device is two frequency dividers and a phase comparator. The comparator circuit produces a voltage proportional to the difference in the frequencies LEAVING the two dividers.

The two dividers are essentially the same except for how configurable they are.

Divider 1 is driven from a crystal oscillator, this is what gives it the overall stability. Whatever crystal frequency you choose, it can be divided by 8, 128, 256, 512, 1024, 2048, 2410 or 8192 by connecting RA0, RA1 and RA2 as appropriate to ground. The result of the crystal frequency divided by the selected number is a fixed reference frequency and will be the same as the frequency difference between one 'step' and the next.

Divider 2 is driven from an external VFO source, the frequency it sees is whatever frequency the VFO runs at. The 'N' pins select a number which is used to divide that frequency by the selected 'N' value. So 'VFO/N' comes out of the divider, it is directly available at the 'fV' pin on the IC.

So you have two signals leaving the dividers, one is fixed by the crystal and 'RA' divisor, the other is the VFO frequency divided by 'N'. The difference between them is produced by comparing them in a phase detector circuit. It gives you the error between the two signal frequencies which you can then use to tune the VFO to make the error zero. When (if) it detects zero error it means (Crystal / RA value) = (VFO / N) and it lets you know by making the LD pin (Lock Detected) pin high.

If you change the 'N' value, the divided VFO frequency will no longer match the divided crystal frequency so the phase detector will again produce an error voltage which you use to tune the VFO so it brings the frequencies together again.

Hope that makes sense!

Brian.

Hi
If I understood this explanation..

example step 25khz xtal 5.120Mhz...
divider external is /10 100Mhz / 10 is 10Mhz... MC145151 divede this to with 2048? 0,0048828125 - 4.8828125khz?

 

[betwixt]

step 25khz (2048*25=5.120Mhz) RAO RA1 RA2 its 101 ( its 1 open ( not connected on the ground) or 5V supply )? = 0 its on the ground in this example.. ?

The RA and N pins on that IC have internal pull-up sources so if you leave them disconnected or make them high, they are interpreted as a '1'. If you ground them they are a '0'.

If you wanted 25KHz steps with a 5.120MHz crystal, the setting would be RA=101 so the reference is 5120000/2048 = 2500 (2.5KHz) then choose 'N' numbers in multiples of 10 so the spacing is 2.5KHz x 10 = 25KHz.

Remember the PLL does not produce the final frequency, the VFO does that so don't expect any output pin to have the frequency you want on it. It isn't a synthesizer but it is the frequency controller when you use an external oscillator circuit.

When you have set the crystal and RA divider to produce the reference, the frequency the VFO will try to produce is 'N' times that reference. Using the example above, with 5.210MHz crystal, RA = 101 gives a reference of 2.5KHz so if the 'N' value is 1000 it would try to produce 2.5MHz. If 'N' was 1001 it would produce 2.5KHz higher and if 'N' was 1002 it would be 5KHz higher and so on.

The PLL produces the voltage to tune the VFO so its divided by 'N' frequency is the same as the reference, it is up to the VFO design to actually be able to produce the frequency.

Brian.

 

[rigmo]

Brain and all ho can answer. sorry explan to me for complite understooding. how to get foruma.
tnx to you an anther guys now I understood part about DIL RA012 part and Xtal.
I do not understood part about DIPs14 on MC145151.
How I get dip sw position for 14DIPswitch
If i need in exsample 98.800Mhz step 50 or 100khz divader 8 10 or 64... ?

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This is schematic since 1993... I lost documentation for calculation...
And now I wont to know how to calculate, if I use different divider and xtal...

 

[rigmo]

Yes I forget to Ask
what is difference between MC145151 vs p2 and MC145152 p2 ?

 

[betwixt]

I do not understood part about DIPs14 on MC145151.
How I get dip sw position for 14DIPswitch

The 'N' pins are a binary number. The pin is a '1' if the switch is open and a '0' if the switch is closed because the switch connects the pin to ground and the IC contains a circuit to make it appear high if disconnected. The binary number is the division ratio, in other words the number the VCO frequency is divided by before it is compared to the reference. To make a frequency from the VCO, work out how many times higher it is than the reference and set that number on the switches. For example if the reference was 10KHz and you wanted to produce 10MHz, the division ratio is 1000 (1000 x 10KHz = 10MHz) so you work out what 1000 is in binary (=00001111101000) and make that number by closing the approriate switches.

To get the step size you want there are several options. The step size is the same as the reference frequency so work out what crystal frequency you need based on the RA pin value and the table in the data sheet. Remember that the DIP switch sets the division ratio so if necessary, add more than one to the binary number to achieve the step you want. For example, if you want 50KHz steps but the easiest reference frequency is 10KHz, just add 5 to the binary number each time so you jump 5 steps at a time.

Note that the highest frequency the MC1415x family of ICs can handle at the VCO input is about 25MHz so you cant produce 98.8MHz directly. There are two solutions to the problem, either add an external divider circuit between the VCO and divider input so it sees a lower frequency and adjust the division ratio accordingly -or- down mix the 98.8MHz to a lower frequency using an external circuit, in which case the division ratio stays the same.

what is difference between MC145151 vs p2 and MC145152 p2 ?

The difference between the 14151 and 14152 is they have slightly different RA divider values and the 14152 has a modulus output instead of a reference frequency output. The modulus control connects to a special kind of external frequency divider that has two different pre-set ratios (for example 64 and 65). It makes it slightly easier to produce some frequencies but at the expense of extra components. The 'p2' just means version 2 of the IC with slightly better performance.

Brian.

 

[rigmo]

Hi Brain
IF I understood this value of external divider (/8 10/ 25/ 64) ( vco ) does not affect the calculation directly
Only important is chosen step on RA DIL vs VCO frequency how many times is higher.. X100 x1000 x1000?
example
N=(Ft/25step)*1000 ( 110MHz N=(110/25)*1000=4400, convert 4400 u 14 bit binary code = 01000100110000

 

[betwixt]

I'm not understanding your question. There is no x100 x1000 x1000.

The reference frequency is the crystal frequency divided by the selected value (using RA) in the table. The result is in Hz.

The VCO frequency will try to be 'N' times the reference. 'N' is a binary number.

The VCO has to be at less than 25MHz or:
1. be divided externally so it arrives at the MC14151 at less than 25MHz, or
2. be down-mixed (have a fixed frequency subtracted from it) so it arrives at less than 25MHz.

Brian.