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Observing noise in ADF4377 output frequencies

Category: Software
Product Number: ADF4377

Hi Team,

We are currently controlling the ADF4377 using an Artix7 FPGA via SPI on our custom evaluation board.

We are able to program ADF4377 for all the frequencies from 800MHz to 12GHz(captured the ADF4377 output on oscilloscope and during this lock detect-LKDKT is also high as per expectation).

Even though we are generating required frequency from ADF4377 with LKDKT high, we are observing lot of noise in the ADF4377 output.

Could you please help us in debugging this issue.

Attached the ADF4377 pll output waveforms for the respective frequencies and below are the register settings we are using to generate the required frequencies.

REGISTER Value
3.2GHz 4GHz 6.4GHz 8GHz
0x00000000 0x18 0x18 0x18 0x18
0x00000001 0x00 0x00 0x00 0x00
0x00000002 0x00 0x00 0x00 0x00
0x00000003 0x00 0x00 0x00 0x00
0x00000004 0x00 0x00 0x00 0x00
0x00000005 0x00 0x00 0x00 0x00
0x00000006 0x00 0x00 0x00 0x00
0x0000000A 0xA5 0xA5 0xA5 0xA5
0x0000000B 0x00 0x00 0x00 0x00
0x0000000C 0x56 0x56 0x56 0x56
0x0000000D 0x04 0x04 0x04 0x04
0x0000000F 0x00 0x00 0x00 0x00
0x00000010 0x20 0x28 0x40 0x50
0x00000011 0x80 0x80 0x80 0x80
0x00000012 0x81 0x41 0x41 0x01
0x00000013 0x00 0x00 0x00 0x00
0x00000014 0x00 0x00 0x00 0x00
0x00000015 0x0F 0x0A 0x0F 0x0A
0x00000016 0x00 0x00 0x00 0x00
0x00000017 0x00 0x00 0x00 0x00
0x00000018 0x00 0x80 0x00 0x80
0x00000019 0xF0 0xF0 0xF0 0xF0
0x0000001A 0x00 0x00 0x00 0x00
0x0000001B 0xAC 0xAC 0xAC 0xAC
0x0000001C 0xC1 0xC1 0xC1 0xC1
0x0000001D 0x00 0x70 0x00 0x00
0x0000001E 0x00 0x00 0x00 0x00
0x0000001F 0x87 0x87 0x87 0x87
0x00000020 0x09 0x09 0x09 0x09
0x00000021 0xD3 0xD3 0xD3 0xD3
0x00000022 0x32 0x32 0x32 0x32
0x00000023 0x98 0x98 0x98 0x98
0x00000024 0x00 0x00 0x00 0x00
0x00000025 0xD6 0xD6 0xD6 0xD6
0x00000026 0x18 0x18 0x18 0x18
0x00000027 0x10 0x10 0x10 0x10
0x00000028 0x27 0x27 0x27 0x27
0x00000029 0xC4 0xC4 0xC4 0xC4
0x0000002A 0x09 0x09 0x09 0x09
0x0000002B 0x00 0x00 0x00 0x00
0x0000002C 0xC0 0xC0 0xC0 0xC0
0x0000002D 0x1F 0x1F 0x1F 0x1F
0x0000002E 0x83 0x83 0x83 0x83
0x0000002F 0x01 0x01 0x01 0x02
0x00000030 0x00 0x00 0x00 0x00
0x00000031 0x09 0x09 0x09 0x09
0x00000032 0x09 0x09 0x09 0x09
0x00000033 0x18 0x18 0x18 0x18
0x00000034 0x08 0x08 0x08 0x08
0x00000035 0x00 0x00 0x00 0x00
0x00000036 0x00 0x00 0x00 0x00
0x00000037 0x00 0x00 0x00 0x00
0x00000038 0x00 0x00 0x00 0x00
0x00000039 0x00 0x00 0x00 0x00
0x0000003A 0x5D 0x5D 0x5D 0x5D
0x0000003B 0x2B 0x2B 0x2B 0x2B
0x0000003C 0x00 0x00 0x00 0x00
0x0000003D 0x00 0x00 0x00 0x00
0x0000003E 0x00 0x00 0x00 0x00
0x0000003F 0x00 0x00 0x00 0x00
0x00000040 0x00 0x00 0x00 0x00
0x00000041 0x00 0x00 0x00 0x00
0x00000042 0x05 0x05 0x05 0x05
0x00000043 0x00 0x00 0x00 0x00
0x00000044 0x00 0x00 0x00 0x00
0x00000045 0x00 0x00 0x00 0x00
0x00000046 0x00 0x00 0x00 0x00
0x00000047 0x00 0x00 0x00 0x00
0x00000048 0x00 0x00 0x00 0x00
0x00000049 0x00 0x00 0x00 0x00
0x0000004A 0x00 0x00 0x00 0x00
0x0000004B 0x00 0x00 0x00 0x00
0x0000004C 0x00 0x00 0x00 0x00
0x0000004D 0x00 0x00 0x00 0x00
0x0000004E 0x00 0x00 0x00 0x00
0x0000004F 0x00 0x00 0x00 0x00
0x00000050 0x00 0x00 0x00 0x00
0x00000051 0x00 0x00 0x00 0x00
0x00000052 0x00 0x00 0x00 0x00
0x00000053 0x00 0x00 0x00 0x00
0x00000054 0x00 0x00 0x00 0x00

ADF4377_PLL_3P2G_4G_6P4G_8G_CAPTURES.zip



  • Here are some debug tips:

    1. Even if you do not have an evaluation board on hand, pls go ahead and install the evaluation board control software (you need to install ACE and then add the ADF4377 plugin. The nice thing about this software is that you can configure the part (frequency, N and R setting, etc) and get a readout of the register settings. You can then compare these to what you are writing. 

    2. In addition to viewing the lock detect signal on the Muxout pin, you can also bring out the R and N counter signals. Check to see if these look clean and are at the frequency you expect. Apologies if you already looked at these and if they were in your set of screen shots. 

    So please try these and let me know how you get on. - Eamon

  • Hi Enash,

    Thanks for your reply.

    Below capture shows the settings configured in ACE Tool to generate 3.2GHz frequency. Even with this configuration, we are observing noise in the ADF4377 output.

    Attached the Register dump as well with the above ACE Tool configuration.

    Below table shows the difference between the register settings currently which we are using and the present ACE Tool capture(As per above configuration).

    ADF4377 3.2GHz
    Register Currently Inuse ACE TOOL
    0x000010 0x20 0x10
    0x000011 0x80 0xC0
    0x00001D 0x00 0x40
    0x00001F 0x87 0xC7
    0x000023 0x98 0x18
    0x000024 0x00 0x04
    0x000026 0x18 0x3B
    0x000027 0x10 0xA8
    0x000028 0x27 0x61
    0x000029 0xC4 0x6A
    0x00002A 0x09 0x18
    0x00002D 0x1F 0x4E

    With the register settings Currently Inuse(as shared earlier), we are observing output of 25MHz when Muxout(REG001D) is programmed for either 0x40 or 0x50.

    But with the new configuration settings as per ACE Tool, we are observing output of 50MHz when Muxout(REG001D) is programmed for either 0x40 or 0x50.

    Attached the Muxout captures for reference.

    Please let me know if this is expected behavior for the given settings and also please suggest the best settings to reduce the noise in the output.

    Note: Even the regiADF4377_3p2GHz_ACE_Tool_configuration_captures.zipster settings shared earlier are taken from ACE Tool.

    Thanks,
    Srikanth.

  • Maybe we can back up a little. and clarify your basic PLL settings

    Fref::

    Fout: 3.2 GHz

    R Counter

    N Counter

    MUXOUT Signal (MUXOUT Register 04: DIV_RCLK/2: 25 or 50 MHz (depending on settings)

    When you say that you are getting high PLL noise, can you characterize that? Do you mean poor phase noise or are you observing the noise floor (in dBm or dBm/Hz) on the FFT. Or are you seeing unexpected spurs?

  • I've not heard back from you and am going to assume that you do not need further assistance. 

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