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LP87745-Q1: LP87745-1 restart randomly

Part Number: LP87745-Q1
Other Parts Discussed in Thread: AWR2944,

Hi Experts

We are using LP87745-Q1 to power AWR2944 while customer find that the power rail of PMIC would randomly drop and then return to normal.

As the picture shows, it seems the PMIC has been restarted. How could we know the root cause of 4 power rail reset?  like thermal protection or input protection?

Thanks 

Ken

  • Hi Ken,

    Are you feeding the watchdog or have you disabled it using the WD disable function on the CS pin? The CS pin must be pulled down to <100 mV to disable the watchdog during startup. 

    The table below lists possible causes of PMIC shutting down and rebooting. Orderly shutdown disables all the regulators and reenables them. Multiple warm resets will cause orderly shutdown as well depending on the set RESET_CNT_THR setting. Additional shutdown mechanisms can be found from Table 8-3. in the data sheet.

    BUCK1 BUCK2 BUCK3 LDO BOOST VCCA VMON1
    Overvoltage Orderly shutdown Disable faulty regulator Orderly shutdown Orderly shutdown Disable faulty regulator Orderly shutdown Orderly shutdown
    Undervoltage Warm reset Disable faulty regulator Warm reset Warm reset Interrupt only Orderly shutdown Warm reset
    Short circuit Orderly shutdown Orderly shutdown Orderly shutdown Orderly shutdown Orderly shutdown N/A N/A

    BR,

    Samuli

  • Hi Samuli

    it is due to that WD is not properly disabled.  The pin is pulled down but affected by another signal.

    Appreciated for your kindly help!

    Ken