LMX2820: Instant Calibration and phase synchronization principle

Amy Luo

Part Number: LMX2820

Hi team,

1. What is the principle of the LMX2820 Instant Calibration?

I can now frequency-hopping using Instant Calibration, but I don't understand the principle of Instant Calibration locking

2. What is the principle of phase synchronization of LMX2820? I want to take a closer look.

The above issues is from one of our customers, I have provided him with the following two documents, but he has the following questions, could you help with further guidance?

Dramatically Improve Your Lock Time with Vco Instant Calibration (snaa342)

How to Phase Synchronize Multiple LMX2820 Devices

1. The first document only describes the benefits of instant calibration, but how is CAPCODE, CORE, and DACISET determined? What is the principle? Why is it faster than FULLASS frequency hopping?

2. The second document only describes the type of phase synchronization, and the example of phase synchronization of the device, and does not explain the principle of phase synchronization. The document shows that the output frequency after phase synchronization has a definite phase difference with fPD. So what is the phase difference? What is its principle?

Best Regards,

Amy Luo

over 2 years ago

0 Noel Fung over 2 years ago

TI__Guru** 112170 points

Hi Amy,

Details of calibration is here: https://www.ti.com/lit/pdf/snaa336

Phase synchronization is used to maintain a deterministic latency between output and input.

After synchronization, the latency is not zero and varies from part to part. As a result, the output phases from multiple devices will not be exact.

0 Amy Luo over 2 years ago in reply to Noel Fung

TI__Expert 6895 points

Hi Noel,

Glad to see your reply.

Instant Calibration is not covered in the attached linked document. Did you give a link to the wrong document?

Regards,

Amy

0 Noel Fung over 2 years ago in reply to Amy Luo

TI__Guru** 112170 points

Hi Amy,

The link describes the calibration and the use of the vco parameters such as capcode, the link also explains why how to reduce vco switching time. Instant calibration do the same thing but is fully automatic.

0 Amy Luo over 2 years ago in reply to Noel Fung

TI__Expert 6895 points

Hi Noel,

The customer has the following queries, could you help with some guidance

If it is the same as a full auxiliary calibration, only the values for CORE, BAND, DAC are automatically given, So where is instant calibration faster than full secondary calibration? Does it automatically give a value that does not need to be calculated?

0 Noel Fung over 2 years ago in reply to Amy Luo

TI__Guru** 112170 points

Hi Amy,

Full assist requires LUT generation and application manually while both of these operations are automatic in Instant calibration. In addition, instant calibration will use register double buffering, output frequency won't change until LUT is applied.

Clock & timing

Clock & timing forum

LMX2820: Instant Calibration and phase synchronization principle