Software for calculating PLL registers in LMX2330
LMX2330 is a very powerful PLL since is has two internal synthesisers.
The circuit has 4 registers which must be filled with data to work properly.
R-reg and N-reg for the RF synth (2.5 GHz)
R-reg and N-reg for the IF synth (510 GHz)
The tricky part is to understand all the registers and settings.
Another tricky part is to calculate good combinations to get the PLL system working.
Below I will show you my software to calculate all the registers in a very easy way.
With this software you can easy calculate many combination for any frequency with just a button press.
Lets take a look at the software shall we.
Details:
At top you will set the Reference Crystal you are using, in this case I use 16.8 MHz (default).
Inside the circuit LMX2330 you have two PLL synth.
RF - which can work up to 2.5 GHz
IF - which can work up to 510 MHz
In the software you will find two identical frame, one for RF Setting and one for IF setting.
In this example I will focus on the RF Setting frame.
You will find a box Ref low and a box Ref high
With these boxes you can set the range you wish to have for the reference frequency in you system (PLL step).
The reason to have a range is to make it possible to find many combination that will make your system lock to desired frequency.
If you have a wide range (as it is as default) you will find many combinations.
The next box is the Freq, here you enter the frequency you wish to lock at ( in this case 144 MHz).
The Max Error box will set the max error you accept for the calculation (in this case 0 Hz)
You can also set some other options as Charge Pump Current, Prescaler, Phase Polarity, 3-state and Power.
The LMX2330 circuit has an output pin FoLD which can be configured for many purposes.
In this case I highlighed RF lock Detect as output.
Now, all you need to do is to press the button Calculate RF.
The software will now list all possible combinations and in this case we got 167 Nr of match.
Look at the high-lighted row of the calculations and I will explain what you got.
The software gives us that R-register should be 168 which will give a reference frequency of 100000Hz.
The N counter should be 1440 to make the PLL lock at 144 MHz.
The Error is 0 Hz as we wished.
You will also find the content for R-register which is 1202A2 Hex and the N-register should be 005A03 hex
R-reg and N-reg.
R-reg should be programmed to 1202A2 hex => 0100100000001010100010 Bin
N-reg should be programmed to 005A03 hex => 0000000101101000000011 Bin
Any computer program or microcontroller can easy send these two bitstreams to the PLL.
Important
The LMX2330 need to configurate both RF and IF all times, even if you only use one of the internal PLLs.
So in this case I will make a default (any value) calculation for IF to get the register data.
Conclusion:
Use the software to calculate the R-Reg and N-Reg for the synth you wish to use.
If you only use one synth, you should make a default (any value) calculation for the other to get the register filled with data.
R-reg and N-reg.
R-reg should be programmed to 001515 hex => 0000000001010100010101 Bin
N-reg should be programmed to 00e7C0 hex => 0000001110011111000000 Bin
The bitsream i s 22 bits and any computer program or microcontroller can easy send these two bitstreams to the PLL.
Please look into datasheeet for more details.
