TUSB4041I: 3.3V is back feeding onto 1.1V rails

Hi Benjamin:

  first not recommend switching DC-DC converter which adding low frequency jitter  to the hub.

    Is  this PMIC  turned on by EN pin ? how the output affect PMIC  enable or disable?

Best

brian

I'm not sure the relevance of this question.  The PMIC turns on when the board is initially powered.  3.3V comes from an independent supply, while 1.1V is created by the PMIC.  The PMIC will not start if there is a residual voltage any rail and TUSB4041I is creating a 0.25V voltage through the hub.  We confirmed this.  This seems like a design defect.  Please advise on how to proceed.

Are there any other loading on 1.1v supply?

i'm not PMIC  expert, let me check with TI PMIC group if it's normal  behavior with 0.25v residual voltage

with 0.25V leakage on 1.1v of TUSB4041, you may need to use normal LDO device to get 1.1v.

Best

brian

Hi Benjamin:

    I saw you post on E2E about  TPS65220. 

    Can you add a delay  for 3.3v  between TPS65220 and  TUSb4041 to make sure TPS65220  turned on first before 0.25V on 1.1v?

    If can't ,  may need to use other Vbus switch with EN pin.

Best

Brian

Hi after more testing we'd like to run a diode on VDDQ which would leave us with a 0.9V core voltage.  The spec is a minimum of 0.99V.  After testing the the hub continues to work at this voltage.  Do you foresee and issues running the core voltage at 0.9V?