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ISOW7840: How does the device work if an external voltage source is applied to the Viso pin?

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Replies: 2

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Part Number: ISOW7840

Hi,

I have some questions about the behavior of this device if voltage is applied to Viso:

1. What happens if the device is in 5V-5V mode -- VCC is 5V and Viso is generating, say 5V at 0A. What happens if 5.5V is applied to Viso? Will the chip use the 5.5V to power the digital signals? Will the internal converter circuitry use any current from the 5.5V supply?

2. Same situation as above, but VCC=0V, and an externally sourced ~5V is applied to Viso. Does the device consume power from this supply? Would it consume whatever the digital pins need, but nothing more?

Thank you,

Ishraq

  • Hi Ishraq,

    Thank you for posting to E2E. If an external power supply is connected to ISOW78xx Viso pin, Viso will either sink or source current based on the external supply level. If Viso = 5V and an external supply = 5.5V, Viso may consume some current as with the case where Viso = 0V. If the external power supply is available, can an ISO7740 or ISO7840 be used instead?

    Please allow me to check the current consumption details over the next 2- 3 days, but ISOW78xx's Viso pin is not designed to be used with external power supplies; using it this way could damage the device.

    In which end application will this device be used?


    Respectfully,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Ishraq, all,

    My apologies for the delayed follow-up; this conversation continued via email. In summary, we don't expect issues or for the device to be damaged when external voltages are applied to Viso within supply voltage limitations of ISOW7840. However, such use is not recommended.


    Thank you,
    Manuel Chavez

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