LMX2582: The LMX2582 VCO core range

Hi, Vicente,

We have some issue for the LMX2582:

1. We use the LMX2582 based on the datasheet, and record the N and FVCO, but there are some differnet between the datasheet and PLLATINUMSIM, and we hav no idea which one is right?

2. Please advise the fasting locking time for LMX2582? We read it in the PLLATINUMSIM is more than 10us;

3. when configuring the initialization of LMX2582, I followed the instructions in the specification sheet to configure the quick lock function, but it couldn't be locked. Can you help me find out where the problem?

Hi Vincente,

When our company is using LMX2582, we found that during frequency switching, the lock signal output by the MUXout (LDTYPE=1) of the chip is 20us later than the measured Vtune. please advise how to solve this issue, thanks.

Hi Zhang, 
I suspect the frequency might not actually be stable. 

Do you have equipment capable of frequency vs time measurements? 
Please refer to the last reply done by Noel to get a better idea of what I am talking about. 
https://e2e.ti.com/support/clock-timing-group/clock-timing-internal/f/clock-timing---internal-forum/1384021/lmx2572lpevm-lock-time/5320658#5320658

If we look at frequency for a wide band, a device can appear "locked" while in reality the output frequency is still settling (analog settling time). 
Only using a narrow band can we directly determine when the device is within the threshold for lock detect to go high. 
This could explain why LD takes a bit longer to go high. 

Regards, 

Vicente 

Hi Vicente,

What optimization methods are available for LMX2594 and LMX2582, which have high spurious frequencies of 100M on each side of the lock frequency?

Hi Zhang, 
These are spurs from your PFD or ref clk (both are 100MHz). 
I assume you see more spurs at 200MHz, 300MHz, etc? 

You can try utilizing the input doubler or multiplier to change your phase detector frequency. 

Regards, 

Vicente 

Hi Vincente,

We have try more multiplier to change the phase detector frequency, but there are no improve, so please advise if there are any other possible cause for this issue, thanks.

Hi Zhang,

I fear these are spurs due to OSCin.

You can try reducing the charge pump to reduce the amplitude of the spurs but I cannot guarantee this will eliminate the spurs altogether.

Regards,

Vicente