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LMK04832: SYSREF output pulse width is only about 5~6 nanosecond.

Shi Zhang
Prodigy 30 points

Part Number: LMK04832
Other Parts Discussed in Thread: LMK04821, ,

My LMK04832's SYSREF frequency is configured to 10 MHz. However, single pulse output of SYSREF is quite strange, which has only about 5 to 6 nanosecond pulse width. And no device (e.g. FPGA and JESD204B ADCs) could recognize such a narrow pulse as a sysref. Normally, this pulse width should be 50 nanosecond, when I use similar configuration on LMK04821. 

Is there any different between LMK04832 and LMK04821 to deal with SYSREF duty cycle correction? I cannot find any configuration instruction about SYSREF duty cycle correction.

Here are my configuration of LMK04832. PLZ help me out. Thank you so much.

  • 0
    Prodigy 30 points

    20230418.tcs

    Something wrong with image posting. Here is my configure file of TICS PRO.

  • 0 in reply to Shi Zhang
    TI__Mastermind 18780 points

    Hi Shi,

    Thanks for the configuration. I have paged our jitter cleaner expert, he will get back to you when he is available.

    Best,

    Evan Su

  • 0 in reply to Evan Su
    TI__Genius 12570 points

    Hi Shi,

    The configuration file looks good and while importing it in the LMK04832EVM setup, it shows correct duty cycle for single pulse SYSREF.

    I believe, you are making SYNC_1SHOT_EN bit to 0, when generating the pulses.

    Thanks!

    Regards,

    Ajeet Pal

  • 0 in reply to Ajeet Pal
    Prodigy 30 points

    Fullscreen 04832.txt Download 
    0x000090
0x000010
0x000200
0x010002
0x01010A
0x0102F0
0x010350
0x010410
0x010500
0x010601
0x010700
0x010802
0x01090A
0x010A60
0x010B40
0x010C20
0x010D20
0x010E01
0x010F55
0x011008
0x01110A
0x0112F0
0x011350
0x011410
0x011500
0x011601
0x011700
0x011808
0x01190A
0x011AF0
0x011B50
0x011C10
0x011D00
0x011E01
0x011F00
0x012020
0x01210A
0x012260
0x012340
0x012400
0x012500
0x012601
0x012711
0x012808
0x01290A
0x012AE0
0x012B50
0x012C10
0x012D00
0x012E01
0x012F00
0x013014
0x01310A
0x013260
0x013340
0x013420
0x013500
0x013601
0x013711
0x013825
0x013900
0x013A01
0x013B40
0x013C00
0x013D08
0x013E03
0x013F00
0x014080
0x014100
0x014200
0x014351
0x0144FF
0x014500
0x014607
0x014718
0x014802
0x014902
0x014A02
0x014B02
0x014C00
0x014D00
0x014EC0
0x014F7F
0x015000
0x015102
0x015200
0x015300
0x015478
0x015500
0x01560A
0x015700
0x015896
0x015900
0x015A0A
0x015BD4
0x015C20
0x015D00
0x015E1E
0x015F3B
0x016000
0x016101
0x01620C
0x016300
0x016400
0x01650C
0x016958
0x016A20
0x016B00
0x016C00
0x016D00
0x016E13
0x017310
0x017700
0x018200
0x018300
0x016600
0x016700
0x016810
0x055500
0x0143D1
0x013900
0x014400
0x0143F1
0x0143D1
0x0144FF
0x014351
0x014352
0x013902

    Hi Ajeet,

    Thank you for your reply. However, the last configuration of 0x143 is 0x014352. The 6th bit of 0x143 is 1. Here is my configuration on my board sent by controller. 

     Especially, plz pay attention to those configuration after 0x055500, which is quite similar on my board with LMK04821. those code is to initialize SYSREF according to datasheet.

    Regards,

    Shi Zhang

  • 0 in reply to Shi Zhang
    TI__Genius 12570 points

    Hi Shi,

    I don't see any issue in the sequence for SYSRF pulse generating, except you are sending appropriate SYNC rising edge at SYNC pin, as you have configured SYNC_MODE as SYNC PIN (Pulser). Please verify the external SYNC input signal.

    You could also try with SYNC SPI (Pulser) by changing SYNC_MODE --> 3 and 0x13E --> 03 for 8 pulses out.

    Thanks!

    Regards,

    Ajeet Pal