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ISOW7821: ISOW7821 load current

Yuxi Liu(Tony)
Intellectual 1360 points
Part Number: ISOW7821

Hi Tier

Could you explain the reason why the load current of VISO pin in 5V to 5V/3.3V condition (130mA) is high than 3.3V to 3.3V (75mA)?

  • 0
    TI__Guru 51910 points

    Hi Tony,

    Thanks for reaching out.

    The driving strength of internal components is higher when input is 5V due to which the device supports higher current while the driving current is relatively lower for 3.3V due to lower input voltage, the output power that can be delivered by the device is relatively lower.

    This is the reason why the output current capability is different for 5V and 3.3V inputs. Let me know if you have any further questions, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Intellectual 1360 points

    Thank you . But in datasheet the output power is 0.65W. So I think 5* 130mA = 0.65, why 3.3V * 75mA is lower than 0.65W?

  • +1 in reply to Yuxi Liu(Tony)
    TI__Guru 51910 points

    Hi Tony,

    The datasheet of ISOW7821 specifies that it supports upto 0.65W of power. For 5V input, it supports 0.65W of output power while for 3.3V input, it supports 0.25W of output power.

    The explanation I provided in my previous response is the reason for this difference, that higher input voltage enables stronger drive leading to higher power support while for lower input voltage, the drive strength is relatively low leading a relatively lower output power. Thanks.


    Regards,
    Koteshwar Rao