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Original question:

LP87745-Q1: NRSTOUT restart

LP87745-Q1: LP87745-Q1 reset every 74s

li liang
Prodigy 50 points
Part Number: LP87745-Q1

Tool/software:

Hi,

May I ask why does the 1V output disconnect for 4ms every approximately 74 seconds when a 2.2k pull-down resistor is already connected to the WD pin.

  • 0
    TI__Genius 16832 points

    Hello Li,

    More information is needed from your side before I can provide a detailed answer:

    1. Do you have the full part number for this device, it would help me answer since each of these are programmed slightly differently?
    2. What output is 1V, which BUCK, and do all BUCKs reset?
    3. Have you readback the interrupts to confirm that the WD is the issue?
      1. Registers: 0x51 & 0x47
      2. I'm assuming yes because you can point to systemic issues
    4. To understand your issue, that after 74 second from turning on the PMIC, the 1V output will reset every 4ms until the power is disconnected, correct?

    BR,

    Nicholas McNamara

  • 0 in reply to Nicholas McNamara
    Prodigy 50 points

    Thanks for your reply! I will explain these as following.

    1. The full part number is LP877451A1RXVRQ1, the same as used in AWR29494.

    2. The output voltage of three BUCKs are 1.8V, 1V and 1.2V respectively. All BUCKs has reset.

    3. As figure attached before, there is a 4ms pull-down occurs every 74s and continues in a cycle until power is diconnected.

    4. At the same time, I am also trying to suppress the restart by feeding the watchdog. Could you tell me what the register address corresponding to the watchdog is?

  • 0 in reply to li liang
    TI__Genius 16832 points
    li liang said:

    1. The full part number is LP877451A1RXVRQ1, the same as used in AWR29494.

    2. The output voltage of three BUCKs are 1.8V, 1V and 1.2V respectively. All BUCKs has reset.

    3. As figure attached before, there is a 4ms pull-down occurs every 74s and continues in a cycle until power is diconnected.

    4. At the same time, I am also trying to suppress the restart by feeding the watchdog. Could you tell me what the register address corresponding to the watchdog is?

    1. Thank you this helps confirm the watchdog long window, which is the 5 seconds which I see the time mark for

    2. Which according to the shutdown sequence, they all should thank you for confirming

    3. Okay, it's systematic, but do you know for a fact that this is being caused by the WD timing out? I see no evidence for this at the moment, so can you please readback the registers from 0x47 to 0x51, these are interrupt registers. Does the microcontroller stop sending the answers for the watchdog, can you show me the traffic that does this?

    4. Please access the resource page that will link to the datasheet for more information, I can't say anymore: (resource link page here)

    BR,

    Nicholas