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TUSB8043A: VIH and VIL of XI

Yuta Nishie
Genius 3250 points
Part Number: TUSB8043A
Other Parts Discussed in Thread: SN74AUP1G08,

Hi,

Could you tell me the VIH and VIL of XI?

Best Regards,

Nishie

  • 0
    Guru 261630 points

    A crystal would output a sine wave, with a rather small peak-to-peak voltage. In other words, XI-XO is (used as) an analog amplifier.

    When using an external oscillator, a digital signal with rail-to-rail voltage would work fine.

  • 0 in reply to Clemens Ladisch
    Genius 3250 points

    Hi Clemens-san,

    Thank you for your reply.

    Clemens Ladisch said:
    When using an external oscillator, a digital signal with rail-to-rail voltage would work fine.

    The customer is thinking of using an external oscillator.
    Am I correct in understanding that the specifications of VIL and VIH are not specified?

    If the specifications are not specified, could you please answer the following?
    For example, is it possible to input the output of SN74AUP1G08 (Vcc=1.65 V) to the XI of TUSB8043A?
    I would like to check if VOH(min)=1.3 V and VOL(max)=0.35 V of SN74AUP1G08 can support TUSB8043A.

    ＊I do not use the SN74AUP1G08 on the board.
    This is just an example as a reference for VIH and VIL.

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    TI__Guru** 114020 points

    When using an external clock source such as an oscillator, XI should be tied to the 1.8-V clock source 

    Best

    Brian

  • 0 in reply to Brian Zhou
    Genius 3250 points

    Hi Brian-san,

    Thank you for your reply.

    I know "XI should be tied to the 1.8-V clock source" because I saw 8.3.7 Input Clock Requirements on the datasheet.

    I haven't received an answer about VIH and VIL. Is it correct that you don't have answer?

    *I am sorry for stating VIH/VIL as VOH/VOL in my previous reply.

    Best Regards,

    Nishie

  • +1 in reply to Yuta Nishie
    Guru 261630 points

    VIL/VIH are not specified because XI is intended to be used with an analog signal, in which case there are no switching thresholds. It is enough for the signal to have peaks above and below 0.9 V.

    Regarding the SN74AUP1G08: the VOL/VOH values are specified for a certain output current. But the XI input has a high impedance, so the actual output current wil be near zero, and the actual VOL/VOH values will be near 0 V and 1.8 V. In other words, the output signal of the SN74AUP1G08 has a much higher quality than that of a crystal. The same applies to other logic devices; any digital output with an I/O voltage of 1.8 V will work fine.

  • 0 in reply to Clemens Ladisch
    Genius 3250 points

    Hi Clemens-san, Brian-san,

    Thank you for your support.

    I will tell the customer.

    I would appreciate it if you could respond again when I receive additional questions.

    Best Regards,

    Nishie