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AWR1243: Couple of questions regarding cascade solution

Faiz Ahmed
Intellectual 460 points
Part Number: AWR1243

Hello,

We have designed our own board with 2 chip cascade solution. We have it working but had a couple of questions:

1)  We use pin B15 to feedback the LO to pin D15 on the master chip to match the delay between master and slave.  How do we configure the master chip to use external LO? We are not sure if the master is using external LO or internal LO. 
2) We are using an external LDO to provide 1V to the RF chain. Has TI noticed any issues with using 1V instead of 1.3V for RF portion of the AWR chip?
Thank you,
Faiz
  • 0
    TI__Guru*** 147854 points
    HI,

    We are checking with our board designer and will get back to you as soon as possible

    thank you
    Cesar
  • 0 in reply to Cesar
    TI__Mastermind 18470 points
    Hi Faiz,

    1) The best resource for AWR1243 Cascade firmware configuration is going to be the AWR1xxx Interface Control Document (ICD) which is released as part of the mmWave Device Firmware Package (DFP): software-dl.ti.com/.../index_FDS.html

    software-dl.ti.com/.../AWR1xx_Radar_Interface_Control.pdf

    Section 5.22.2 Cascaded Device Mode provides an example API call list to get Cascade mode operational. This includes a call to the AWR_CHAN_CONF_SET_SB with either CASCADING_CFG = 0x0001 (indicating a master device which generates the LO).

    What this CASCADING_CFG description does not say, is that this cascade mode configuration expects the star-network LO configuration described in the AWR1243 Cascade application note (www.ti.com/.../swra574a.pdf).

    So, there should not be anything else to do in your dual device configuration as long as you are following the topology laid out in that app note and the cascade mode configuration described in the ICD.

    2) As long as your external LDO provides sufficient current and meets the ripple noise requirements at the BGA RF1/RF2 power pins of the AWR device, there is no problem. Please see the AWR datasheet for the ripple noise requirements .

    Please let me know if that answers all of your questions on these topics.

    Thank you,
    Randy
  • 0 in reply to Randy Rosales
    Intellectual 460 points

    Hello Randy,

    Thank you for checking. Regarding question 1:

    From the firmware configuration file there doesn't seem to be a difference between 4-chip and 2-chip solution for LO part. Does the master output LO from both D1 and B15? We used a modified configuration for LO distribution in order to avoid a splitter (previous thread: link)

    Thank you,
    Faiz

  • 0 in reply to Faiz Ahmed
    TI__Mastermind 18470 points
    Hi Faiz,

    I will check this last point out for you. Might need a few days to get a response back.

    Thanks,
    Randy
  • 0 in reply to Randy Rosales
    TI__Mastermind 18470 points
    Hi Faiz,

    In the current DFP firmware, both of the FMCW_CLKOUT and FMCW_SYNCOUT are enabled in both the 4-chip and 2-chip mode. Please let me know if that answers your question.

    Thank you,
    Randy