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IWR1642: issues in IWR1642 when changing PMIC from lp87524b to lp87524J.

wang york
Intellectual 715 points
Part Number: IWR1642
Other Parts Discussed in Thread: TPS7A88, UNIFLASH

when I change the PMIC from 87524B to 87524J, and BUCK2_VOUT should be 1.0V and connect directly to IWR1642 for RF part.

When this circuit is ready, i found i can flash images into IWR1642 chip, but when i change back to normal mode (remove the jumper), it can't boot up, and even can't connect to CCS.

So what is the problem?

  • 0
    TI__Mastermind 37500 points
    Hello,
    There are several sections that need to change for the swra577 modification.
    a) remove the TPS7A88 dual 1.3v LDO, add two ferrite beads for 1v3_RF1, 1v3_RF2 (which is now 1v0).
    b) remove the TPS78801 single 1.8v LDO, add ferrite bead for 1v8
    c) replace the LP87524B with LP87524J

    Power supply modification - you need to check that the LP87524J L1,L2,L3,L4 outputs are the proper voltage.
    - you need to check that the output voltages to the decoupling capacitors (pg 3 of the schematic) are correct
    - for CCS, Visualizer, Uniflash - make sure the 3v3 Board power is OK

    - try to format the flash, with the programming jumper attached
    - try to attach with CCS to the M4 processor

    - make sure you change the RFLDO Bypass function in your code
    - try to reprogram the device again
    - if the board will not autostart, try to hold nRST pushbutton, the turn on power, then release nRST

    The digital power for the mmwave sensor is 1.2v, 1.8v, and 3.3v. Only the 1.8v was modified in the new power arrangement.

    Regards
    Joe Quintal
  • 0 in reply to Radio-Joe
    Intellectual 715 points
    hi,
    Thanks for your information.

    My problem earlier is leave the RF power input unconnected, which only to test digital sub system, and it seems the chip has self detection function, and it will not boot when BUCK2_VOUT is not connected.

    Further, I found another issue.

    My plan is to utilize the internal LDO which may has a better performance than direct PMIC (LP87524J ) input to work at non low power mode and compare the performance with 1.0V directly feed into IWR1642 for low power mode

    Low power configuration steps is as follows:
    1. turn on power, and system boot automatically.
    2. configure low power mode by command, lowPower 0 1

    The issue is when I run command lowPower 0 1 and sensor to start, it will run into error , error code is [-203685690]
    while i set lowPower 0 0, it work well, and the RF input is 1.0V.

    Non low power configuration steps is as follows:
    1. turn on power, and system boot automatically
    2. change PMIC BUCK2_VOUT from 1.0v to 1.3v
    3. use lowPower 0 0 mode to start sensor

    This steps works OK.

    So I want to go to the key questions.

    1. does 1642 has a self-detection function when booting up. when RF input is 1.3V, it will automatically set to normal mode; when RF input is 1.0V, it will automatically set to low power mode, and when RF input is 0V, it will not boot up. These 3 phenomenon fit my observation.
    2. my non low power configuration steps has risks? it is already set to low power mode, but i have changed PMIC voltage from 1.0v to 1.3v, but it still can work, but it is not good for system.

    Am i right?

    Thank you.
  • 0 in reply to wang york
    TI__Mastermind 37500 points

    Hello,

    Yes the mmwave sensor will not start without the voltages needed.  1v2, 1v8, 3v3, are required.   The 1v3 is needed for RF functions, if the RFLDO Bypass function is used, the input should be 1.0v; otherwise the input should be 1.3v.

    The device has VMonitor circuits internal, and they are used as part of the self diagnostics.

    The suggestion is to bring the PMIC out of reset, at the desired voltage, either 1.0 or 1.3, while holding the nRST signal low.  Once you have the desired voltage, you can follow the nRST release and boot sequence.

    One of the things that causes damage, is to have the 1v3 input, and then use RFLDO bypass, this exceeds the rating of internal sections of the device.   We have done tests on the 1243, 1443 with 1.0v used at startup, I will ask about 1642, and update this further.

    Regards,

    Joe Quintal