Part Number: LMX2492EVM
Other Parts Discussed in Thread: LMX2491
Hi all,
I posted about this during the summer. I'm having trouble getting the LMX2492EVM to produce ramps.
Since I was limited in the frequency range due to a lack of appropriate equipment, I added a new VCO in the 400 - 800 MHz range and rerouted the components to reflect this.
There are a few steps I'm still confused about to produce a ramping signals:
1. The OSCin reference signal is my signal generator. I normally set it between 10-20 MHz (again due to a lack of high-end scopes). I can't find what the voltage range should be for the signals on the datasheets. I normally set OSCin to be 2-3 Vpp but that might be too high since the RFout and RFout/2 are always in the 50 mV range. I have no clue what the output voltage range should be. the 10-50 mV RFout voltage leads me to think that the whole thing is not working at all or that I need to attach an amplifier at the output if this is really what the output voltage range normally is.
2. When setting up ramps, I write the values in and then click on "Ramp enable". Then I click on "Write all registers" under USB communications. Sometimes the FFT of the output changes significantly so that is why I continue to "write all registers" even if it isn't necessary.
3. In the "User Controls" tab I changed the MUXout_MUX to Output R and Output R/2 on separate occasions.
4. Something really weird that I've noticed (may be a common issue in general) but it appears that the output shows a waveform only when the input is being measured. Do you know what causes this?
5. I really need to show the ability to produce ramps of various lengths by November 10th. If anyone could give me a basic procedure and tell me what fundamental mistakes I'm making, I'd be forever grateful. I doubt there is any hardware issues because I was really careful soldering the SMD components during the addition of the new, lower frequency VCO.
Thanks for your time.
Here are a few screenshots below:
