LMX2492EVM: Chirp rate and lock time

Amit kumar

Prodigy 90 points

Part Number: LMX2492EVM

Dear Texas team,

We want to know two things in LMX2492EVM module which is mentioned below,

1. What is the maximum chirp rate we can get in this EVM board?

2. What is the analog lock time of PLL in this EVM board?

over 2 years ago

0 Noel Fung over 2 years ago

TI__Guru** 108550 points

Hi Amit,

Loop bandwidth is over 400kHz.

For EVM information, please read the EVM user's guide. https://www.ti.com/lit/pdf/snau160

Theoretical analog lock time is approx. equal to 4 / loop bandwidth.

You can use PLL Sim to design the loop filter and simulate PLL performance. https://www.ti.com/tool/PLLATINUMSIM-SW

0 Amit kumar over 2 years ago in reply to Noel Fung

Prodigy 90 points

In EVM user guide we didn't find the value of maximum chirp rate. Can you give me this information.

0 Noel Fung over 2 years ago in reply to Amit kumar

TI__Guru** 108550 points

Hi Amit,

The ramp engine increments VCO frequency once every phase detector cycle.

Given the max. fpd = 200MHz. The max. ramp rate is also 200MHz.

0 Amit kumar over 2 years ago in reply to Noel Fung

Prodigy 90 points

actually, i am little confused about the maximum chirp rate of EVM, it should be in MHz/sec. so it is 200 MHz/sec or else?

0 Noel Fung over 2 years ago in reply to Amit kumar

TI__Guru** 108550 points

Hi Amit,

The ramp engine can change VCO frequency every 5ns ( = 1 / 200MHz). If your application requires a 1MHz frequency change per ramp, then the chirp rate is 200kHz/ns.

Clock & timing

Clock & timing forum

LMX2492EVM: Chirp rate and lock time