SNAA342 September   2020 LMX2820

 

  1.   Trademarks
  2. 1 Overview of Frequency Hopping
  3. 2 Integrated VCO Overview
    1. 2.1 Integrated Silicon VCO Structure
    2. 2.2 Robustness and Consistency of VCO Calibration
  4. 3Components of Synthesizer Lock Time
    1. 3.1 Write Time
    2. 3.2 VCO Calibration Time
    3. 3.3 Analog Settling Time
  5. 4Improving VCO Calibration Time With the LMX2820
    1. 4.1 Improving LMX2820 VCO Calibration With Partial Assist
    2. 4.2 Full Assist Method of Improving VCO Calibration Time
    3. 4.3 Instant Calibration – The Ultimate to Blazing-Fast VCO Calibration
  6. 5Conclusion
  7. 6References

4.1 Improving LMX2820 VCO Calibration With Partial Assist

The partial assist method can be used to improve the lock time for this example with the LMX2820. To do this, some values were chosen close to, but not equal to, the starting values Table 4-1 shows.

Table 4-1 VCO Calibration Start Values

Setting

Actual Value

No Assist Start Value

Partial Assist Start Value

VCO_SEL

1

7

1

VCO_CAPCTRL

186

0

180

VCO_DACISET

336

300

330

Using this partial assist method, the VCO calibration time was reduced from 174 μs to 80 μs. This is a worthy reduction, but instant calibration can do better. For more information and examples on partial assist VCO calibration, see the Streamline RF Synthesizer VCO Calibration and Optimize PLL Lock Time Application Report.