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Original question:

SN65HVD33: About Enable Time of Driver

SN65HVD33: Driver Enable Time

Masanori Tachibana
Genius 5350 points

Part Number: SN65HVD33

Hello support team,

I asked the same question before.
Just in case, please teach me again.

1. As can be seen from Figure 15 in the datasheet, I think enable time would be about 30 ns, if the common mode voltage applied externally to the bus pin is less than Vcc (3.3 V).
Is my understanding correct?

2. The specification of "Driver enable delay with bus voltage offset" is specified separately. And the maximum value of it is 900 ns.

I think this is maximum value (worst value) of tpZH1 (Propagation delay time, high-impedance-to-high-level output) or tpZH2 (Propagation delay time, high-impedance-to-low-level output), whose conditon is that within the range of -7 to 12 V (recommended operating conditions) of voltage is applied externally to the bus pin.
Is my understanding correct?

3. If the voltage applied externally to the bus pin is 0 V ~ Vcc (3.3 V), I I think that the value of "Driver enable delay with bus voltage offset" is same as tpZH1 or tpZL1 and maximum value of it is 45 ns or 35 ns.
Is my understanding correct?

Sincerely,
M. Tachibana

  • 0
    TI__Guru 62920 points
    Hello Tachibana-san,

    I believe you are correct, but we will double check this to confirm and get back to you next week. Today is a holiday for our US site.

    Max
  • 0 in reply to Miguel Robertson
    Genius 5350 points

    Hello Max-san,

    Thank you for confirming.
    I'm waiting for your additional information.

    Sincerely,
    M. Tachibana

  • 0 in reply to Masanori Tachibana
    TI__Guru 62920 points
    Tachibana-san,

    I've now had a chance to look into this in more detail.

    1. Yes, you are correct - with bus voltages lower than 3.3 V the HVD33 device's enable time will be < 45 ns. (To answer your third question, this is similar to the conditions used for the tPZH1 and tPZL1 specifications that do not specify an offset, so the same values would apply.)

    2. Yes, the driver enable delay can become longer with certain bus voltage offsets, so this value is specified separately than the typical no-offset case. The maximum value specified here would apply across the recommended operating bus voltage range that you mentioned.

    Please let us know if you have any further questions.

    Regards,
    Max Robertson
  • 0 in reply to Miguel Robertson
    Genius 5350 points

    Hello Max-san,

    Thank you for your kind advice.
    It was very helpful.

    Since our customer use SN65HVD33 on the opposite side of the bus line and both GNDs are connected at almost the same potential, I think the bus voltage will not exceed 3.3 V.
    Therefore, I think the Enable time can be estimated less than 45 ns.

    Sincerely,
    M. Tachibana