we are using ADRF6755 we want calculate REFIN freq registers. if our Ref in pin freq is 24 MHz after using Doubler and 5 bit divider we need 18.5 MHz our requirement how to calculate and get 18.5 MHz to PFD.
It is not possible to generate an 18.5MHz PFD from a 24MHz Reference on this device. Please see the table below for the possible PFD values you can achieve using 24MHz Reference Frequency. 16MHz is the closest one to your target of 18.5MHz.
In the table above I have highlighted in red those PFDs which are outside the specified range of 10 - 80MHz as shown at the bottom of page 6 on the datasheet.
If you want an 18.5MHz PFD you could get this by using
Reference = 37MHz (/2 = 18.5)
Reference = 74MHz (/4=18.5)
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