Other Parts Discussed in Thread: LMX2492, , LM6211
Hi,
I am using LMX2492 for synthesis of 9 to 10.4 GHz frequency.
I have my customised board with LMX2492EVM as a reference for schematic and layout. VCO used is HMC1162. XO used is CWX813 (same as TI LMX2492EVM).
I am using the active loop filter as my VCO needs more than 5 volts for targeted frequency. Loop filter uses LM6211 opamp (same as TI LMX2492EVM).
Register values are derived from the TICS Pro default configuration mode. All the reserved registers are written as 0.
I am using my own controller to write the PLL registers using MicroWire Interface.
Nothing at all is happening at CPout pin.
I have made following observations:
1. Register writing is Ok. I can enable and disable the PLL using POWERDOWN bit. Also reading the registers gives me appropriate readings (Lets say a reserved register cant be changed. So it is being read as its POR vale).
2. XO outout to REFin pin is ok. The 100 MHz (2.4 V to 0.8 V) wave can be seen using MSO in PLL REFin pin.
3. No activity at CPOUT pin (Whereas other PLL(ADF4159) shows some activity using MSO at CPOUT for same hardware). Loop filter goes to 12 V output as CPOUT(-IN) goes to 0 and +IN at 2.5 V.
4. Tried changing bits like CPPOL, PFD_DLY, DLD_PASS_CNT, DLD_TOL, DLD_ERR_CNT and Change Pump Gain to various values, but no effect observed.
I have 2 doubts about LMX2492 IC
1. What if my feedback is faulty and not going properly to PLL? My VCO output is 2 dBm and radiation level is so high that I get -20d Bm,10.4 GHz signal everywhere near PLL VCO Loop. I don't know how to check the feedback.
2. Can my PLL IC has a problem such that its digital section is working but RF section is not working?
Please help !!