Hi Team,
Customer is looking for a PLL solution that can realize fast frequency switching.
I saw that lmx2485 supports Cycle slip reduction and fastlock functions.
Do we have corresponding test data that can show the effects of Fastlock and CSR at different fComp frequencies?
Also, do we have any further explanation on how Fastlock and CSR work?
BR
Adrian
Hi Adrian,
LMX2485 datasheet has a section describe CSR and fastlock. LMX2470 datasheet has a little more information. basically the concept is, during frequency switching, we make the loop bandwidth wider (using the additional shunt resistor) and at the same time increase the charge pump current. As a result, the loop bandwidth will be much higher than normal, and therefore the lock time will be shorter. After changing the frequency, the PLL will resume to using the normal loop filter and charge pump current. For example, at normal state the loop bandwidth is 2kHz. During frequency switching, the loop bandwidth is 20kHz, that's why the loop time is shorter and cycle slip problem become less severe.
additional training slide here: https://www.ti.com/lit/pdf/snap002?keyMatch=CYCLE%20SLIPPING
We can use PLL Sim (www.ti.com/.../PLLATINUMSIM-SW to simulate the lock time. Check the user's guide from menu bar.
