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请教隔离输出电压选择问题

Category: Hardware
Product Number: ADUM5404

ADUM5404的VDD1为3.3V,如果VSEL管脚

悬空会怎样?



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[edited by: StephenV at 6:14 PM (GMT -4) on 10 May 2024]

Thread Notes

  • Hi kuangfeng,

    The VSEL is meant for the Output Voltage Selection. When VSEL = VISO, the VISO setpoint is 5.0 V. When VSEL = GNDISO, the VISO setpoint is 3.3 V. This pin is weakly pulled to high. In noisy environments, tie this pin either high or low. For your case with it being left hanging, the VSEL will have a weak pull-up to VISO.

    Best,

    amitmadan

  • 谢谢回复!

    在VDD1为3.3V,VSEL悬空的情况下,实测VISO先为5V,大约2min后变为3.3V,请问这种情况正常吗?

  • Hi kuangfeng,

    This part is not operable with a 3.3V input and 5V output, so there are no guarantees in how that would operate. To ensure you VISO remains at 3.3V, the VSEL must be tied to GNDISO for the 3.3V output, the only validated operating case for a 3.3V input.

    Best,

    amitmadan

  • 谢谢回复!

    贵公司发售的这款芯片会有批次性的差异么?大约2年前我买的这款片子,在VDD1为3.3V,VSEL悬空的情况下,实测VISO为3.3V;去年买的片子,就是我之前咨询的情况:在VDD1为3.3V,VSEL悬空的情况下,实测VISO先为5V,大约2min后变为3.3V。当然,正常的设计应该按照你们数据手册上的要求来,我只是想就上述相同用法(尽管不符合数据手册要求)的两批片子的不同表现进行进一步的咨询,想知道是什么原因。

    谢谢!

  • Hi kuangfeng,

    Lot to lot variation is subjected to approximately 20% process variation. The weak pull-up on VSEL is not a tested parameter so its impedance is not guaranteed, but VSEL must be tied to GNDISO for the 3.3V operation to function correctly.

    Best,

    amitmadan