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TUSB4020BI-Q1: Unused Pin and Power Consumption Inquiry

Evan Wang
Expert 6350 points
Part Number: TUSB4020BI-Q1

Hi All,

We have 2 questions when using TUSB4020BI-Q1.

1. Since we only need the TUSB4020BI-Q1 as a USB 2 HUB, no power switch or SMBus/I2C is needed.

May I know how to configure below pins?

  • SCL / SMBCLK (Pin 2)                         -> Leave unconnected?
  • SDA / SMBDAT (Pin 3)                         -> Leave unconnected?
  • SMBUSz (Pin 22)                                 -> Leave unconnected?
  • PWRCTL_POL (Pin 21)                        ->Leave unconnected?
  • GANGED / SMBA2 /HS_UP (Pin 35)   -> Leave unconnected?
  • FullPWRMGMTz /SMBA1 (Pin 36)       -> Leave unconnected?
  • GRSTz (Pin 11)                                    -> Add 1uf cap to GND?

2. We would try to reduce the power consumption of the IC.

May I know whether TUSB4020BI-Q1 has any power saving mechanism even the I2C and SMBus are not used?

I would also like to know why the current consumption are the same under below 3 conditions(Power-on/Disconnect/Suspend).

And what is the definition of each of them?

Looking forward to your reply.

Thank you.

  • 0
    TI__Guru**** 156171 points

    Hi,

    1. These pins can be left unconnected if not used - the internal pullup / pulldown resistors will keep them in the default setting (no battery charging, no overcurrent, no SMBUS). 

    For GRST, besides 1uF to GND, please make sure the proper power-up sequence is followed as outlined in section 7.7.

    2. Disconnect means physical disconnection from the USB host on the upstream port, no cable attached. Suspend means a USB Suspend condition on the USB bus. But the low power mode consumption is the same among the three conditions.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 6350 points

    Hi David,

    Appreciate your comment.

    For item 2, since the source might come from battery directly so we are worried about the quiescent power consumption.

    It seems that there is no way to reduce the power consumption of this device, am I right?

    And since we only need the USB interface(No power switch/battery charging are needed), could you also recommend another device with lower PD?

    But I don't think we have other option for it with AEC-Q100.

    Thank you.

  • 0 in reply to Evan Wang
    TI__Guru**** 156171 points

    Hi,

    For AEC-Q100, we do not have another device that can support lower power number.

    Thanks
    David