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JESD204B ParallelSync with LTC6953 Reference Distribution Cannot Comple Synchronization Between LTC6952s

Category: Hardware

Hello, I am hoping to use the LTC6953/LTC6952 combination in a ParallelSync operation with the LTC6953 providing the reference distribution in Figure 35 in the LTC6952 datasheet. And the initial configuration of registers are as follows:

LTC6953 - {0x25, 0x08, 0x42, 0xc0, 0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0x13, 0x00,    0x00, 0x80, 0x00, 0x00,    0x08, 0xc0, 0x01, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x00, 0x00, 0x00,    0x00, 0x80, 0x00, 0x00,    0x08, 0xc0, 0x01, 0x00, 0x22};

LTC6952#1 - {0x15, 0x2a, 0x00, 0x00, 0x22, 0x22, 0xcc, 0x01, 0x00, 0x14, 0x13, 0x00,    0x98, 0x80, 0x28, 0x00,    0x98, 0x80, 0x28, 0x00,    0x99, 0x80, 0x38, 0x00,    0x99, 0x80, 0x33, 0x00,    0x99, 0x80, 0x29, 0x00,    0x99, 0x80, 0x28, 0x00,    0x9d, 0x80, 0x14, 0x00,    0x9d, 0xf3, 0xd0, 0x00,    0x9d, 0xf3, 0xcb, 0x00,    0x9d, 0xf3, 0xc1, 0x00,    0x9d, 0xf3, 0xc0, 0x00, 0x22};

LTC6952#2 - {0x15, 0x2a, 0x00, 0x02, 0x22, 0x22, 0xcc, 0x01, 0x00, 0x14, 0x13, 0x00,    0x99, 0x80, 0x28, 0x00,    0x99, 0x80, 0x75, 0x00,    0x99, 0x80, 0x6f, 0x00,    0x99, 0x80, 0x61, 0x00,    0x99, 0x80, 0x5e, 0x00,    0x9d, 0xf0, 0x14, 0x00,    0x9d, 0x80, 0x14, 0x00,    0x9d, 0xf4, 0x0d, 0x00,    0x9d, 0xf4, 0x07, 0x00,    0x9d, 0xf3, 0xf9, 0x00,    0x9d, 0xf3, 0xf6, 0x00, 0x22};

Following the example in datasheet, the outputs in LTC6953 which connect to LTC6952 #1,2 EZS-SRQ are set to pass through mode, and the EZS-SRQ in LTC6953 is connected to GND. I am using a 100MHz reference and no dividers in the LTC6953. However, I couldn't catch any pulse in the oscilloscope and those two LTC6952s couldn't be synchronized, that is, the output clocks in LTC6952#1 and LTC6952#2 don't have a fixed phase difference.

Is there anyone able to shed any light as to what I might be doing wrong?

Thanks for any help.

  • And I tested EZS-SRQ inputs of LTC6952 #1 and LTC6952 #2 using the single request mode in the oscillosthere.

  • Hi,

    From LTC6953  registers you send, I have found that REG0x06 to REG0x0A didn't have default values that stated in the datasheet. It is advised that default values also uploaded to chip on power up. After that you can write only changes

    And LTC6952 registers, it seem that adel value is high but it depends on your VCO frequency.

    Are you using LTC6952 Wizard or ACE software to determine register values? I highly recommend using ACE Software and LTC6952 and LTC6953 Plugins or LTC6952 Wizard to determine register values.

    What is your reference frequency and VCO frequency? Are you using Evaluation Board or custom board?

    Regards,

    Emrecan