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Original question:

TUSB4041I-Q1: TUSB4041I-Q1 high current drawn by VDD 1.1V rail

TUSB4041I-Q1: Anomalously high current consumption and strange GRSTz behavior

Matthew Burger
Prodigy 10 points
Part Number: TUSB4041I-Q1
Other Parts Discussed in Thread: TUSB4041I

Tool/software:

Hello,

We are using the TUSB4041I in an on-board USB switch application for a power consumption sensitive (automotive) environment. During testing, we have noticed anomalously high current consumption by the TUSB4041 and a seeming lack of impact by the GRSTz pin. I have attached the relevant portions of our board schematic for your reference.

We are unfortunately unable to readily measure the power consumption of the 3.3V and 1.1V USB power supplies separately from rest of the board during operation, but we did isolate them in order to take a baseline measurement. The following are my observations:

 

Total Board Current Consumption @ 12V Input (mA)

Condition

GRSTz Not Asserted

GRSTz Asserted

USB Supplies Physically Disconnected

< 1

N/A

USB 1.1V Supply Disabled (3.3V only active)

35

35

Both Supplies Active

As Shown in Schematic

45

45

GRSTz cap removed

45

45

Previous + PWRCTLx pins shorted to Ground

64

64

Previous + FULLPWRMGMTz resistor removed

78

78

Previous + PWRCTLx ground jumpers removed

43

43

In all cases, there were no upstream or downstream devices connected to the switch.

The switch itself seems to function properly when an upstream device (our compute module) or downstream device is connected, but this current consumption is untenable in the case where we put our upstream device into sleep/shutdown. 

Our questions:

  1. Are we using the reset functionality correctly? We know our 3.3V supply is sequenced before the 1.1V supply but, based on our reading of the datasheet, an active reset assertion should take care of this; however, reset assertion appears to not have any effect on power consumption.
  2. What could be causing our high current consumption across the board? These values seem high, even setting aside the reset issue.

Thank you for any help you can provide!TUSB4041I_circuit_schematic.pdf

  • 0
    TI__Guru*** 131275 points

    Hi Matthew:

        We recently found  there is high current on 1.1v supply when GRSTz i s low, current could be  high as 320ma , what is current limit for your 1.1v supply?

    Best

    Brian

  • 0 in reply to Brian Zhou
    Prodigy 10 points

    Hi Brian,

    Thank you for your help!

    We do now observe the high current draw of the 1.1V rail when GRSTz is low. After additional testing, our specific issue seems to be a combination of two issues:

    1. Sequencing of the 1.1V and 3.3V rails, and
    2. The state of the upstream USB_VBUS pin.

    Because we are not using the TUSB4041 in a traditional detached USB hub application, we need to manually drive USB_VBUS low when we want our system to sleep. Doing so drops the current consumption of the TUSB4041 to less than 3 mA @ 12 V.

    We consider our issue tentatively resolved at this point.