problem ramp generation

Hi Maged, 

Thanks for sending the configuration and register values. 

I couldnt observe any error on the register configuration. 

I have couple of questions? 

Have you ever disable the ramp and checked the single tone performance of the ADF4159? Can you read lock detect from MUXOUT?

What happens to VTUNE voltage when you set the PLL for fixed frequency operation?

What happens to Vtune voltage when you set the part continuous sawtooth ramp? 

Thanks,

Emrecan

Hi emrecangidik,

Thank you for your quick response; I really appreciate it.

First, as I mentioned earlier, I only receive a single tone at a specified frequency. I have no problem at all with single tone performance, though I haven't checked both lock detect from MUXOUT, or the tune voltage, but I'm going to check them and reply ASAP.

Second, for Vtune voltage during continuous sawtooth ramp, it will be difficult for me, unfortunately, I have no oscilloscope 

Could you reply for this question, "since this PCB is a custom one, does getting a tone at the desired frequency mean that both HW and SW to program the ADF4159 are correct?  " or the answer needs more investigation

Regards

Thanks

Maged

Hi emrecangidik,

Q1:"Have you ever disable the ramp and checked the single tone performance of the ADF4159? Can you read lock detect from MUXOUT?"

A1: I have no problem at all with single tone performance, YES I can read lock detector it gives High

Q2: "What happens to VTUNE voltage when you set the PLL for fixed frequency operation?"

A2: it gives fixed VTUNE voltage that changes at different frequency value as expected

Q3: What happens to Vtune voltage when you set the part continuous sawtooth ramp? 

ok now for any type of ramp lock detect gives LOW, very small fixed VTUNE voltage, and VCO output is fixed at the start of its frequency band

I am still trying to find a reason, but I couldn't manage, 

Could you reply for this question, "since this PCB is a custom one, does getting a tone at the desired frequency mean that both HW and SW to program the ADF4159 are correct?  " or the answer needs more investigation

Regards

Thanks

Maged

Hi emrecangidik,

I'm still waiting your reply

regards

maged

Hi, 

If the single tone performance is good. Then, I dont expect any problem with the hardware. Sweep parameters might incorrect. 

Another important point is the opamp in the active loop filter.

What is the supply voltage of the opamp? and what is the voltage value on the positive input of the opamp. This voltage should be set to 1.65V.

Thanks,

Emrecan

Hi Maged, 

I couldnt find anything out of ordinary on the schematic. Can you try to lock the VCO to different frequency values while ramp is disabled? One other recommendation would be testing the circuit by modifying the loop filter to achieve 55 degree phase margin. 

Thanks,

Emrecan

Hi Emrecangidik,

thank you for your support and advice, i used logic analyzer and it was a problem with code for SPI CS. now, i can perform frequency ramp with the chip. I hope this post may help others.

thanks again Emrecan

regards

maged