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TPS65218D0: PGOOD always low

Howard Zou
Genius 12365 points
Part Number: TPS65218D0
Other Parts Discussed in Thread: AM4376,

Hi, my customer is using TPS65218D0 to power AM4376.

When VCC_5V drops below 3.1V, PGOOD and PWR_EN will drop to 0. Even if VCC_5V rises above 3.1V and becomes stable, the PGOOD and PWR_EN could not go back to high. Why?

  • 0
    TI__Mastermind 30280 points

    Referring to your schematic:

    • Why are both R232 and R25 populated? R232 should be marked as DNI (do not install) so that AC_DET is connected to GND and the PMIC will try to turn on every time VIN > VUVLO (2.75V)
    • What is value of C219? The recommendation for DCDC4 is to have 47uF + 0.1uF capacitors at output. Since your schematic only shows C219, my guess is this is not 47uF and I can see you do not also have 0.1uF cap in parallel

    Referring to your scope shots:

    Look at VIN. It is very noisy before PGOOD goes low. If you measure DCDCx outputs when PGOOD goes low and VIN is very noisy, I expect you will see one of these regulators is violating VPG or VOV spec due to load transient, which would cause the PMIC to shutdown.

    You can try to test with STRICT = 0b (bit 2 of CONFIG1, Register 0x13) which loosens VPG limit and disables VOV. If your system stays on long enough, you can write to PMIC by I2C using Linux commands.

    The best way to see if DCDC4 is the source of the VPG or VOV fault would be to remove resistor R19 to disconnect the PMIC DCDC4 output from VDD_33 rail and try to power on the system again. If it works, then DCDC4 is the cause of the issue and you can try to use 47uF + 0.1uF output capacitors to see if they fix the issue. If VIN is still very noisy, you should check your power supply to see if it is the true root cause of the DCDC4 issue.