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LMX2820EVM: Lock Detecting is not caught

Juseong Lee
Prodigy 10 points

Part Number: LMX2820EVM
Other Parts Discussed in Thread: LMX2820

Tool/software:

Hi, i'm Programming LMX2820 EVM.

I want to use Instant calibration to achieve instant PLL control.

Problems occur when controlling the range of 12.5 GHz to 22.6 GHz in 100 MHz steps with a cycle of 10 ms.

I'm running the control and Lock Detect is not caught at a random frequency, and even when I set it to a different frequency, it's still in Low state.

The frequency comes out but it is stuck in an error state.

How can I solve this problem?

  • 0
    Prodigy 10 points

    I solved this problem by setting DBLR_CAL_EN = 0, INSTCAL_DBLR_EN = 1. Thanks.

  • 0 in reply to Juseong Lee
    TI__Guru** 120060 points

    Hi Juseong,

    Please find below the recommended programming sequence for Instant Calibration.

    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)