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ADF4377
Recommended for New Designs
integer-N phased locked loop (PLL) with an integrated voltage controlled oscillator (VCO) ideally suited for data converter and mixed signal front end...
Datasheet
ADF4377 on Analog.com
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:
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.
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.