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AFE7444EVM: Cannot see DAC A output after following instructions and video to place AFE7444EVM in loopback mode

Prodigy 40 points

Replies: 8

Views: 172

Part Number: AFE7444EVM

I have read through all the user manuals and application notes for the AFE7444EVM to place it in Rx-Tx loopback mode.  I found the attached configuration file which I found by searching other threads on this same topic.  I have my signal source set to 1800 MHz @ -11 dBm.  This is attached to A_IN1.  I have my spectrum analyzer set to 1800 MHz with 50 MHz bandwidth attached to IOUTA.

I power up the AFE7444EVM by itself.  It is not attached to the FMC carrier.  I launch the AFE7444EVM GUI and follow all the steps prescribed in application note SLAA871 (see attached). I use the attached configuration file to program the registers in the low-level tab.  I then turn on the RF generator and check for IOUTA output but only see what looks like a leakage spur which is -90 dBm down.

I tried different inputs and outputs with the same result.  I also note that the AFE7444EVM is only pulling about 1 amp of current.  The loopback video shows the AFE7444EVM attached to the FMC carrier and it is pulling over 4 amps. Assuming the power to the AFE7444EVM is not sourcing the FMC carrier in the video, it appears there is something not turning on after configuration.

I have also checked register 0x7E and it it is set for 0x1F which is consistent with mode 4 setting prescribed in the SLAA871 application note.  I also checked jumper JP9 and it is set in the 2-3 position. I also looked at other registers set by the attached config file in the low-level tab and they are consistent with the file.

I have exhausted all ideas at this point and need some help.

Regards,

RickAFE74xx as a single-chip wideband repeater using loopback mode_slaa871.pdf2350.AFE74xx_RX_to_TX_LoopBack_pass.cfg

  • Hi Rick,

    Everything you are doing seems right except the current drawn by the EVM. Can you double check that current limit of AFE power supply is 5A? Can you also try with increased input voltage of 6V? EVM should pull >2A when mode 4 configuration is done. AFE EVM is sourcing power from FMC.

    Regards,

    Vijay

  • In reply to Vijayendra Varma Siddamsetty:

    Vijay,

    I can adjust the voltage to 6V easily.  However, the power source has a limit of 3A.  You mentioned the AFE7444EVM normally pulls about 2A.  So, this should be OK?  Also, I do not have the FMC carrier connected.  I am using the AFE7444EVM by itself.  Should this matter because you mention it is sourcing power from the FMC carrier but the instructions say you don't need to use it?  I am confused.

  • In reply to Richard Matsick:

    Hi Rick,

    EVM is *not* sourcing power from FMC. Sorry I said otherwise earlier by mistake. 

    As you said it's only pulling 1A, I mentioned that it should be easily more than 2A. As shown in the user' guide (below), 5A supply is needed. If you use less than that during configuration, device will try to pull more current and voltage will drop at some instant due to current limit and device will get into a state where it draws less current (around 1A in this case). It looks like it's not hitting current limit. But current limit should be the reason for this behavior. 

    Regards,

    Vijay

  • In reply to Vijayendra Varma Siddamsetty:

    Vijay,

    I was finally able to source a 6VDC 5A power brick (strange that it did not come in the box?)  I repeated the exact same steps with the same result.  I have attached screen shots from the AFE74xx GUI showing the setup.  I think I have a bad board.  I have consulted with other engineers here and they agree.  Please advise next steps.

    Rick

  • In reply to Richard Matsick:

    Hi Rick,

    I will test loopback for mode 4 on an EVM to make sure. However due to winter break, I might not get a chance to set up an EVM in lab until early next week. I will let you as soon as I test this.

    Regards,

    Vijay

  • In reply to Vijayendra Varma Siddamsetty:

    Hi Rick,

    I have verified loopback mode functionality on an AFE7444EVM. I found that the config file you attached is incorrect and doesn't work. Please use the attached config file for loopback mode configuration. This is also available in the AFE7444 secure folder (can be accessed at ti.com/mysecuresoftware). If you don't have access to this folder, request access at: www.ti.com/.../swlicexportcontrol.tsp

    Regards,

    Vijay

    LoopbackConfigFile_with_cont_sysref (2).cfg

  • In reply to Vijayendra Varma Siddamsetty:

    This resolved my issue.  Thank you.  We are wondering what the differences are between the file posted a while back and the new one you provided?  We would like to know specifically what changes were made.

    Thank You,

    Rick

  • In reply to Richard Matsick:

    Hi Rick,

    The only difference between the files is RBD value of TX JESD (Register 0x7E in TX_DUC_P0 page). RBD was set to 0x1F in the config file posted earlier. In the file I sent now, RBD value is 0x0A. It is expected for some range of RBD values to not work. 

    I verified that the default value of RBD 0x0F is working for the loopback mode. So there's no need to update this value in loopback configuration. I attached the configuration to set AFE in loopback mode (without RBD register programming). LoopbackConfigFile_with_cont_sysref.cfg

    Regards,

    Vijay