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ISO7321 level translation and Vcc levels

Jeramie Bianchi
Expert 3315 points
Other Parts Discussed in Thread: ISO7321C

Hi,

Currently, I'm looking to use ISO7321C for two voltages on Vcc. 

We have the VCC1 set to 3V3

VCC1 : 3V3

GND1: 0V

 

and VCC2 set to ~5V, 

VCC2: -43V

GND2: -48V

 

According to the tables provided in 6.5 and 6.6, the VCC's are recommend to be within 10% of either 3v3 or 5V. So the question is, will the isolator still function correctly when the 10% relative voltage is exceeded? As 3v3 and 5V is larger than the 10% difference, or is there built in level translation to allow for one Vcc to be 3.3V and one to be 5V. It seems to mention translation on first page of datasheet.

Lastly, is the -43V and -48V even possible on Vcc2 and Gnd2? Seems it will violate abs max spec on these pins even though effective voltage is 5V.

Thanks,
Jeramie

  • 0
    TI__Intellectual 2200 points

    Hi Jeramie,

    Your application scenario is perfectly acceptable. 

    The tables are provided separately for 3.3V and 5 V operation. If one side is used with 3.3V and other with 5.5V, the electrical parameters that depend on both supplies, such as propagation delay, will be between the the values given in the  3.3V and 5.5V tables.

    For ISO73xx, VCC1 and VCC2 can be in the continuous range from 3.0V to 5.5V with respect to GND1 and GND2 respectively.  GND1 and GDN2 can be at any potential as long as the difference between the two is less than +/-560 Vpk or 400 Vrms as defined in table 8.3.1.2. 

    Rgds,

    Anant