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ISO122: ANALOG ISOLATION

sabitha m
Prodigy 40 points
Part Number: ISO122
Other Parts Discussed in Thread: ISO224,

Hi, Im using ISO122JU for analog signal isolation. Im isolating 0 to 3.3V with isolated power supplies . +VS1(15V) and -VS1(15V ground not negative voltage) and +VS2(iso 15V) and -VS2(iso 15V ground), and on applying 0 to 3.3V as Vin and its respective ground is tied to -VS1 or GND1 .  Im not getting the same input as output . Im getting the output voltage around 12.8V on the output side of IC with respect to Iso 15V ground. Please suggest a solution for this problem.

Thanks

Naveen

  • 0
    TI__Guru 52492 points

    Hi Naveen,

    The negative power supplies -VS1 and -VS2 should not be tied to GND, they should be tied to a negative voltage of at least -4.5V. Please see POWER SUPPLIES in section 7.5 Electrical Characteristics of the datasheet.

    Is this for a new design? If so, I would strongly recommend the ISO224.

  • 0
    TI__Guru**** 176131 points
    Hi Naveen,

    On page 5 of the ISO122 datasheet you will see that the minimum power supply requirement is +/-4.5V. The -VS1 and -VS2 need to be at least 4.5V below ground for the device to work properly. Can you get the 15V sources to look more like +10/-5 (similar to Figure 21 in the datasheet) and see if that resolves the problem?