RoadTest: RoadTest Review the TI LMX2582EVM
Evaluation Type: Evaluation Boards
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?:
What were the biggest problems encountered?: Long delivery period.
Today we are going to look at LMX2582EVM. LMX2582EVM is a High Performance, The LMX2582 device is a low-noise, wideband RF PLL with integrated VCO that supports a frequency range from 20 MHz to 5.5 GHz. The device supports both fractional-N and integer-N modes, with a 32-bit fractional divider allowing fine frequency selection. Integrated noise of 47 fs for 1.8-GHz output makes it an ideal low-noise source. Combining best-in-class PLL and integrated VCO noise with integrated LDOs, this device removes the need for multiple discrete devices in high performance systems.. The PCB is optimized for performance as well as designed for easy customization of the loop filter. An LED is designed for quick visual check on the PLL lock status. With an on-board oscillator, setup process only requires a 3.3V power supply and an included USB2ANY module. The software is simple, with an intuitive and user friendly GUI .
Connecting module to computer
Nice thing about this lmx2582evm development board is that it comes with programmer, that can load correct register over USB to LMX2582 device, so you don't have to deal with complex register maps and so on. If not this USB2ENY module, i would not be able to generate any clock from this EVM, this is very complicated device. I am more familiar with Altera PLL, that can work from 1MHz up to 200-400MHz, but this is completely different beast. You can download software from here : After downloading software i noted that the are no file extention, you have to manually change snac014e to snac014e.zip. After that you can open zip with multiple programs.
TICS Pro - LMX2582 GUI
This is how GUI looks like. It looks simple but in 10 minutes i was unable to output any frequency. This was very frustrating. But after reading datasheet was able to finally get it working. Since i have MDO3104, i was able to capture some spectrograms. While GUI does work, on board crystal oscillator is not that precise, that means you will not be able to get exact frequency. But you can tweak it with fractional PLL, no problem at all
In time domain signals also look quite good. At the output node there is 100pF capacitor fro DC blocking. At lower frequency's you will get horrible waveform, so i just soldered 4.7uF to make it more representative at lower frequency. It is hard to tune it for correct frequency , PLL and VCO are very picky where the optimum frequency is, so if you messing around with registers, not all the time you will get stable clock. But then you do, it is down to last number with basically no visible jitter
In this shot i set trigger to 0, and shifted time base by 10us ( that translates to 1000 period's of this 100MHz signal). After that, i set Persist on, and was zoomed to rising edge ( again, trigger was 10us ago)
To my surprise ( yeah right, best VCO PLL with industry leading phase noise) , it was sooooo clean, my cope was limiting factor here, it just to good for equipment i have. Just take a look at that, it is zoomed as close as i can, 400ps/div
Conclusion;This is very good and simple PLL-VCO to get frequency you need. Only thing is that you have to carefully select registers where PLL is stable. That why the TICS - Pro tool is so useful, it helps you to create config map for your registers, so you can compile that to micro controller or FPGA. Ability to set nearly any frequency you want makes me want to make wide band frequency ( or more precise ) clock generator for my lab that is under construction, with some STM32 for the GUI. I really starting to like this module, and will find a use in my lab or in my work, because in my job we deal with lasers, and to get any frequency you want from laser oscillator will be usefull to our clients, since right now we are only limited to Altera Cyclone 4 PLL, that is no where near as capable as this one, and we do care about jitter, so this will fill our needs for synchronization of electronics to laser. Only downside of this LMX2582EVM is the cost. And the cost is high , ready ? 300$. While the chip itself cost only 10$. I get that if you working with ultralow jitter, you usually have deep pockets, so 300$ is nothing to you. Also PCB material looks like exotic one