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HD3SS3220: Question of pull-up resistor on VBUS_DEC and open drain pins.

Motoyasu Hattori
Genius 11105 points
Part Number: HD3SS3220

Hi.

My customer has the following questions.   Could you please advise us? 

*1.
According to datasheet P.6, parameter R(VBUS), (External resistor on VBUS_DEC pin) is Min 880, MAX 910ohm.  On the other hands, on datasheet P.7, parameter RVBUS is Min 855, MAX 920ohm.  So we are confusing.  Why is different?   Could you please let us know the recommended pull-up resistor value?

*2.
According to datasheet P.5, we can find the typical 200kohm on R(p_ODext) External pull-up resistors on Open Drain pin.   We seem these resistor's value is pull-up to 5V.   How about the resistor value on 3.3V pull-up?   Could you please let us know the recommended external resistor values on 3.3V-pull-up?

Thanks and best regards,
M.HATTORI.

  • 0
    TI__Guru 64326 points

    HI,

    1. The typical recommendation is 900k +/- 10%. P.6 shows the typical operating range that we recommend for the device. P.7 reference is the absolute conditions for the VBUS_DET pin. 

    2. 200k ohm can still be used even for 3.3V. Please refer to section 7.3.12 VDD5 and VCC33 Power-On Requirements on pulling up the open drain pins to a voltage other than VDD5. 

  • 0 in reply to Malik Barton57
    TI__Genius 11105 points

    Hi,

    Thank you for your support.

    Your answer is as follows, but could you please let us know the reason why datasheet selects 200kohm?

    >>2. 200k ohm can still be used even for 3.3V.

     

    Also, we can find the following on the datasheet P.27, "8.2.1 Design Requirements".

    What do you mean "Smaller values can be used"?

     

    My understanding is as follows:  Is it correct?   Please let us know.

    If users select 200k ohm pull-up registers on both case of 5V line and 3.3V-line.  HD3SS3220 is operated correctly.  If they select smaller registers (such as 100k ohm), HD3SS3220 is also operated correctly, however, leakage power (current) is increased.

    Please advise us.

    Thanks and best regards,
    M.HATTORI.

  • 0 in reply to Motoyasu Hattori
    TI__Guru 64326 points

    Hi Hattori,

    200K is a weak pull-up that allows the open drain GPIO of HD3SS3220 to pull down the node voltage below the VOL max spec. If pull-up is too strong ,much less than 200K,  The node voltage cannot be pulled down. Smaller values can be used but do not use smaller than ~10k. Keep in mind that other internal pull-ups may be on the node as well, using a weaker value can keep the equivalent resistor values in the acceptable range.  Your understanding is also correct leakage power will increase as pull-up gets stronger.