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PLL Programming project

PLL Programming project

The LMX2316 is MICROWIRE programmable with a maximum frequency of 1.2GHz. This project was in the iDEN band so we actually had 3 frequencies we needed to generate.
I had the need to test a frequency synthesizer design that had the controller separate. So the end result was to use a BASIC STAMP 2 ( as recommended by a RF engineer ) that would program the PLL. The PLL I needed to use was National Semiconductor?s LMX2316

The two NOT discussed here were in the 700MHz band and its application is proprietary. The 56MHz signal is used throughout a system that is doing upconversion and downconversion of these iDEN band frequencies. I had an old copy of National Semiconductor?s ?CODELOADER? software that would help you figure out what values to program into the PLL depending on your configuration.


My reference oscillator was 20MHz and phase detector frequency was 250kHz. I would recommend placing a 3RD order low pass filter at the output of the PLL but as close to the VCO as possible. You want a filter with a small bandwidth (at the output frequency of the PLL) to help reduce any spurs that may have been created from the PLL. If you see harmonics with a 250kHz spacing from your main signal, then you have a problem.

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