• State Resolved
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 21 subscribers
  • Views 56 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

LMX2820: LMX2820 instant calibration

?? ?
Prodigy 30 points
Part Number: LMX2820

Tool/software:

HI!

After the LMX2820 instant calibration initialization, the frequency was changed from 5.65GHz to 10GHz. The LD lock time is 6 seconds. Procedure
Without power off, 10GHz lock off after even calibration:
R1:0X57A0
R0:0X6430
R0:0X6420

At this point change the frequency to 8GHz and then turn even calibration on again:
R1:0X57A1
R0:0X6430
R0:0X6420

The LD lock time is 82ms.
Please ask why the locking time required for instant calibration is so long in this case.
Can I shorten the lock time?

  • 0
    TI__Guru* 95060 points

    Hi There,

    Your programming procedure is not correct, see below the recommended programming sequence.

    Initialization register setting
    1. Set DBLBUF_PLL_EN, DBLBUF_CHDIV_EN, DBLBUF_OUTBUF_EN, DBLBUF_OUTMUX_EN = 1
    2. Set DBLR_CAL_EN = 0; INSTCAL_SKIP_ACAL = 0
    3. If VCO doubler is required, set INSTCAL_DBLR_EN = 1, otherwise set this bit to 0
    4. Set INSTCAL_DLY = T x fosc (in MHz) / 2^CAL_CLK_DIV, where T = 2.5 x CBIASVCO / 0.47µF. CBIASVCO is the bypass capacitor at pin 3
    5. Configure other registers to lock to 5.65GHz without any calibration assist
    6. Set INSTCAL_PLL_NUM = 2^32 x (PLL_NUM / PLL_DEN)
    Programming
    7. Vcc power up LMX2820
    8. Program all the registers, LMX2820 should lock to 5.65GHz
    InstCal calibration
    9. Program INSTCAL_EN = 1
    9.5 run Index routine
    10. Program R0 (with FCAL = 1), calibration will begin
    11. Wait 100ms
    12. Program R0 (with FCAL = 0) to complete the calibration
    13. If LD pin did not turn HIGH, program RESET = 1 to reset LMX2820. After LMX2820 is reset, repeat Step 8 to 12
    Changing VCO frequency
    14. Program INSTCAL_PLL_NUM, PLL_N, PLL_NUM and PLL_DEN (if their value have change)
    15. Program R0 (with FCAL = 0) to change VCO frequency

    9.5 Index routine
    1. Program R106[10] = 1 (0X6A 0400)
    2. Program R107[5:0] = 0 (0x6B 0000)
    3. Program R108 = 0 (0x6C 0000)
    4. Program R109 = 0 (0x6D 0000)
    5. Program R106[9:0] = 514 (0x6A 0602)
    6. Program R106[11] = 1 (0x6A 0E02)
    7. Program R106[11] = 0 (0x6A 0602)
    8. Repeat step 5 to 7 for R106[9:0] = 515 to 519
    9. Program R106[10] = 0 (0x6A 0000)

  • +1 in reply to Noel Fung
    Prodigy 30 points

    HI！

    Sorry, I may not have expressed clearly. I have programmed the lmx2820 to accomplish instant calibration and been able to change the frequency point as well. However, in subsequent use of the chip, I need to turn off instant calibration and then turn instant calibration back on, and the chip stays powered up at all times during this process. At this time, the lock time of instant calibration will be very long, about 80ms. by the way, I don't know the function of registers R106, R107, R108, R109. Do I have to program these registers?