Software for calculating PLL registers in LMX2322
Below I will show you my software to calculate the 2 PLL registers R divider and N divider.
With this software you can easy calculate many combination for any frequency with just a button press.
Both N-register and R-register are 18 bit long. (see datasheet for details)
The databits is shifted in the PLL on the rising edge of the clock pulse.
Now, let's make a calculating example:
Let's say you want to lock your receiver to NOAA-17 satelite which is at 137.62 MHz.
Our IF is 10.7MHz so the PLL should lock the VCO at 137.62 +10.7 = 148.320 MHz
I enter that value into the Freq input.
Since I use a 13MHz to drive the reference frequency I enter the value into Xtal input.
The Ref low and Ref high set the calculating range for
PLL frequency.
Press Calculate button
In the box below you will see all possible combinations to obtain close match for PLL.
First you see R-counter, Ref frequency, N-counter,
Error, R-reg, N-reg.
Look at the marked line. R-counter is set to 650 which gives: 13e6 / 650 = 20000Hz as Ref frequency
If N-counter is set to 7416, the PLL will be 7416* 20000 = 148.320MHz
The ERROR is 0 meaning we got perfect match for this frequency.
Now, look at the R-reg and N-reg.
R-reg should be programmed to 001515 hex => 000001010100010101 Bin
N-reg should be programmed to 00e7C0 hex => 001110011111000000 Bin
Any computerprogram or microcontroller can easy send these two bitstreams to the PLL.
