The LMX2485E Evaluation Board simplifies evaluation of the LMX2485E 2.6 GHz/0.8 GHz PLLatinum™ dual frequency synthesizer. The primary function of this board is to evaluate the LMX2485E device performance at low RF input frequencies, which is 50 MHz.
The board enables all performance measurements with no additional support circuitry. The evaluation board consists of a LMX2485E device, an RF VCO module and RF loop filters built with discrete components. The SMA flange mount connectors are provided for an external reference input, an RF VCO output, and a power connection. A cable assembly is bundled with the evaluation board for connecting to a PC through the parallel port. By means of MICROWIRE™ serial port emulation, the CodeLoader software included can be run on a PC to facilitate the LMX2485E internal register programming for evaluation and measurement.
The VCO used on the evaluation board is a Sirenza VCO190-52U. Using a 5 Volt supply, the frequency range of the Sirenza VCO190-52U is specified to cover 51 to 53 MHz with a 0.5V to 4.5 V control. The LMX2485E device is powered from a 3.3 V regulated supply, which gives a Charge Pump output dc voltage swing of 0.5 to 2.7 volts for optimum performance. Charge Pump output voltage can be measured at TP1. With these voltages, the VCO output frequency will nominally be 48.6 to 49.6 MHz. No IF VCO is attached. Therefore, the IF section is powered down for all measurements.