Hello,
My customer is considering replacing the MAX2870 with a TI LMX2487.
Could you please provide data on the lock time of the LMX2487 under the following or similar conditions?
If not, please provide examples of various lock times for 3GHz of the LMX2487.
Thank you.
JH
Hi JH,
MAX2870 is a synthesizer (PLL + VCO) while LMX2487 is a PLL only device.
Our cross reference is LMX2572, LMX2582 are LMX2592.
The picture in your post shown the lock time reduction from below topology. This is a common fast lock technique to reduce the analog lock time by increasing the loop bandwidth during lock acquisition. Since it has four VCOs insides the chip, there is a VCO selection process which will also consume lock time. It seems that this specification is not written in the datasheet. Total lock time = programming time + VCO selection time + analog lock time.
Our synthesizer does not have the above fast lock feature, however, our VCO selection process (we called it VCO calibration) is controllable.
You can select Auto-calibration or full-assist.
Auto-calibration, users do not need to do anything, the chip will pick the right VCO, calibration time will depend on the reference clock frequency and configuration, usually it is <100µs.
With full-assist, there is virtually no VCO calibration time, the total lock time (excluding programming time) could be <50µs.
Details of calibration and lock time can be found in below application note.
https://www.ti.com/lit/an/snaa336a/snaa336a.pdf
