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AWR1843: AWR1843: Power module problems LP87702-Q1

Guillermo Villalba Calvillo
Prodigy 60 points
Part Number: AWR1843
Other Parts Discussed in Thread: LP87702-Q1

Hello,

My company has designed a radar based on the AWR1843 reference design. In the initial tests it has worked correctly but we have found that sometimes, immediately after turning it on, it stops working. It happens that when we analyze the problem we see that the LP87702-Q1 regulator has stopped working, returning a voltage of 3.3V at the 1.23V output and 0V at the 1.8V output. Always when we do the tests it fails with the same problem. Does anyone have any idea why this happens?

Greetings and thanks in advance.

  • 0
    TI__Guru 58035 points

    Hello ,

    Could you clarify if when you turn ON the module the output voltages are indeed correct at 1.23V and 1.8V? Only after some usage it goes to 3.3V and 0V?

    Regards,
    Vivek

  • 0 in reply to Vivek Dham
    Prodigy 60 points

    Hello,

    When I turn on the power module the voltages are correct, and when I sometimes add the radar module is when this integrated fails, but there is no short circuit in the radar module.

  • 0 in reply to Guillermo Villalba Calvillo
    TI__Expert 8730 points

    Hello,

    Can you please provide the below information:

    - Schematics of your board.

    - Do you have two modules/PCB's (power supply board and Radar board) separately? If so, please check whether there is some cross connections happening on the connector side?

    PMIC cannot output 3.3V and I am suspecting that this 3.3V is forced externally through something and this causes PMIC to turn off.

    Regards,

    Murthy

  • 0 in reply to Krishnamurthy Hegde
    Prodigy 60 points

    Hello,

    - Yes, of course I am attaching the schematic of the power module.

    - Yes, it is correct the design is separated by a connector. When the integrated LP87702-Q1 fails, it no longer recovers. I have unsoldered the connector and I have measured continuity between 3.3V and 1.23V and there is still continuity, so the connector is not. the continuity is in the integrated LP87702-Q1itself. I have unsoldered this IC and there is continuity between pins 13, 14, 15 and 16. For some reason that I don't know, the integrated breaks down in this part.

    Thank you.

    20190417_V001_GVC_CARCIS_RADAR_POWER.pdf

  • 0 in reply to Guillermo Villalba Calvillo
    TI__Guru 58035 points

    Hello,

    Can you share the other board (with AWR device) schematics also?

    Regards,
    Vivek

  • 0 in reply to Vivek Dham
    Prodigy 60 points

    Hello,

    I attach the schematic that you request.

    Thank you.

    20190417_V001_GVC_CARCIS_RADAR_AWR1843.pdf

  • 0 in reply to Guillermo Villalba Calvillo
    TI__Expert 8730 points

    Hello,

    I checked the schematics and didn't find anything strange with it. Just that additional 22uF capacitor needed on 1.8V rail for improved stability, but with this device should not get damaged.

    This device is being used by multiple customers since last 2-3 years and we have never faced such issues and hence I do not believe that there is any systematic issues with the device. Are you connecting the Radar board when PMIC board is already on or are you connecting the boards first and then turning it on? Hot plugging the boards can cause significant transients on the power supply. Also, please get the pre regulator and LDO schematics reviewed to make sure that it is not causing any overshoots on 3.3V supply line to damage the PMIC.

    Only PMIC is getting damaged and all other components are working fine? I think you need to identify when exactly PMIC gets damaged as it looks like it fails only sometimes and not always. Please check the switch signals, input/output voltages during start up/shutdown to see whether there is some strange spikes on these signals. Also please take a look at your PCB layout to see whether there are some layout weakness around1.23V rail.

    Regards,

    Murthy