LMX2571: how long the channel switch require

Hi Verna,

33ms is not right with the internal VCO, when did your start triggering the test equipment? Were you using external VCO?

With internal VCO, the total switching time is equal to (1)programming time + (2)VCO calibration time + (3)analog PLL lock time. You should ignore the programming time in your measurement. Depending on the reference clock frequency, VCO calibration time will be less than 1ms, in general. Analog pll lock time depends on the loop filter bandwidth, approx. equation is lock time = 4 / loop bandwidth.

Hi Noel,

Thanks for reply.

From customer,

1.We used external VCO;
2.Value of components at loop filter was the same as value recomended in your datasheet;
3.It is trigered by the last rising edge of CS for PLL when I measure lock time;
4.Configuration in simulating is the same as actual configuration.

SCH as following, the channel 1 of oscilloscope is connected to TP8 (CS), channel 2 is connected  to TP11 (PLL LD OUT), triggered by the falling edge of channel 1

Hi Verna,

Could you share the simulation file?

What is the frequency switching programming sequence? are you doing F1 F2 switching?

The frequency switching programming is 326.65MHz to 396.65MHz,or 396.65MHz to 326.65MHz in the same VCO(F1),and trigered by the last rising edge of PLL CS when I measure lock time,It's mean to the time from the last rising edge of  PLL CS to frequency stabilization.---------------------------------------------------

326.65MHz to396.65MHz

HI Noel，

There is a problem with uploading simulation files. Could you send me an email? I'll get back to you with the simulation files.

B&G,

Verna

VERNA.HONG@arrowasia.com