PLL using LMX2301 IC.

Presently I am experimenting with the LMX2301 PLL IC from National Semiconductors. I am using my faithful VCO design , but this time using SMD parts. The VCO circuit remains the same for all my PLLs and is shown below

The LMX2301 is a high performance frequency synthesizer designed for RF operation up to 160 MHz. It is fabricated using National's ABiC BiCMOS process. LMX2301, which employs the digital phase lock loop technique, combined with a high quality reference oscillator and a loop filter, provides the tuning voltage for the voltage controlled oscillator to generate a very stable, low noise local oscillator signal. Serial data is transferred into the LMX2301 via a three line MICROWIRE ^TM interface (Data, Enable, Clock). Supply voltage can range from 2.7V to 5.5V.

The LMX2301 features very low current consumption, typically 2 mA at 3V. The LMX2301 is available in a TSSOP 20-pin surface mount plastic package.

PCBs (VCO and PLL) for the proto type are ready. I would be using my Personal Computer (PC) to load the code in the PLL and test it out. The Code loader software is available on the National Semiconductor site. After successfully testing it out , I would be using a Microcontroller to do the job.

The Application circuit of the LMX2301 is standard and is mentioned in the Data Sheet of the IC. The Charge pump would be providing the control voltage to my VCO to lock it somewhere in the VHF region. I am planning to use a 10 Mhz crystal for the reference Oscillator in the PLL design.

The design philosophy I am using is that the VCO and the PLL are on different PCB called the daughter cards which would be integrated using a Mother board. The reason being that I can use different PLL design and plug it in on the Mother board. The Mother Board would supply the Power and Interconnection between different daughter cards.

More details would follow as the project progresses.