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TUSB8041 / Control GRSTz pin at Power-Up

S.Satoshi
Guru 21685 points
Other Parts Discussed in Thread: TUSB8041

Hi All,

I understand that there is the sequence requirement between GRSTz and VDD/VDD33 as stated in Figure 2 of datasheet. But the EVM has only decoupling 1uF capacitor on GRSTz. Does it means that we do not need to control GRSTz pin at power up to make delay following this sequence requirement?

Best Regards,

Sonoki / Japan Disty

  • 0
    TI__Guru 60870 points
    The TUSB8041 has an internal pullup on GRSTz. For most applications, the passive reset circuit created by the external cap and internal pullup provides an adequate reset pulse on GRSTz. We ask that customers verify this in their design, since they may need to vary the value of the external capacitor. Also, if a customer system ramps 3.3V before 1.1V, an active reset may be required because the internal pullup on GRSTz is connected to the 3.3V rail.
  • 0 in reply to JMMN
    Guru 21685 points
    Hi JMMN,

    Regarding power up sequence, can we ramps 1.1V before 3.3V? Is there any timing requirement between 1.1V and 3.3V at ramps 1.1V first if it can be accept?

    Best Regards,
    Sonoki
  • 0 in reply to S.Satoshi
    TI__Guru* 76130 points
    Hello,
    It is OK to ramp VDD11 before VDD33, in this case you will have to use the external capacitor connected on GRSTz in order to meet the power-up timing described in datasheet.
    Regards