LMX2820: Instant Cal

Hi Noel,

In a related thread you provided the following procedure to run instant calibration.

I noticed a discrepancy between these steps and what is in the datasheet.

In steps 8 - 10 below, FCAL_EN is set to 0, then to 1, then back to 0.

In the datasheet page 26, there are only writes to R0 to set FCAL_EN to 1, then to 0. there is no initial write to FCAL_EN to set it to 0.

Is the datasheet wrong?

Also what is happening exactly in the chip when instant cal is initialized at F = 5650 MHz? Does the LMX2820 step through a internal sequence of test frequencies from 5.65 GHz to 11.3 GHz to generate the cal data for all the VCO cores?

Thanks
K

Please follow the following procedure to run instant calibration.

1. Open TICS Pro and select EVM default mode configuration
2. In User Controls page, check all Double Buffer bits
3. In PLL page, uncheck DBLR_CAL_EN in Instant calibration box
4. Vcc power up the EVM
5. Press Ctrl+L to program the EVM to lock to 6GHz
6. Set INSTCAL_EN = 1 in Instant calibration box
7. Type 5650 and then Enter in the VCO box (PLL_NUM, PLL_N and INSTCAL_PLL_NUM will be programmed automatically)
8. Uncheck FCAL_EN in the VCO calibration box
9. Check FCAL_EN
10. Uncheck FCAL_EN and wait for a while (VCO will lock to 5650 MHz)
11. Change VCO frequency, for example, type 5800 and then Enter in the VCO box (PLL_NUM, PLL_N and INSTCAL_PLL_NUM will be programmed automatically)
12. Click Calibrate VCO button (this will write R0 once, VCO will lock to 5800 MHz)
13. Change VCO frequency to 6200 MHz
14. Click Calibrate VCO button (this will write R0 once, VCO will lock to 6200 MHz)