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ISO1212: Threshold Calculation

Brian Wang0928
Genius 11650 points
Part Number: ISO1212

Hello,

Here is the design requirement of threshold ON & OFF as below. 

Threshold_ON setting is ok with 15V, but Threshold_OFF is NG it's about 13.8V. Could you help to clarify why with the setting below, the threshold_OFF can not meet 5V? thanks. 

24V,typ Input Voltage

Data Rate 1MHz

Bi-directional type Sink & Souce

15V for threshold_ON

5V for threshld_OFF

Rsense is 470ohm

Rthr is 2200ohm

The result:

Vih is 14.9V

Vil is 13.8

  • 0
    TI__Intellectual 2160 points

    Hi Brian,

    According to IEC 61131-2 Type 1 switching characteristics, The OFF state is from 0 to 5V and ON state is 15V and above. That says the device needs to be OFF at all times for voltages ≤ 5V and ON at all times for voltages ≥ 15V. The switching can happen anywhere between 5 & 15V. Our device's VIH and VIL meets all the requirements mentioned in the standard.
    VIH = 14.9V and VIL = 13.8V is in the switching range which is acceptable.

    Thanks
    Vikas J