ISO7721: Low-level output current limitation

Part Number: ISO7721

Hello team,

Could you please let me know how much current ISO7721 output can sink at low level with VCCo=5V?

I recognize TI only guarantee IOL <4mA, but I'd like to know the potential value which could work.



  • Hi Itoh-san,

    ISO7721 do not have any source or sink currents limits implemented internally, hence, they can source or sink current based on external loading conditions. Since the datasheet only guarantees ±4mA at VCC = 5V, sufficient measures to be taken to limit the current into or out of isolator output to make sure it doesn't exceed the datasheet ratings.

    When ISO7721 output is connected to a CMOS or TTL digital input, we expect the source / sink current is going to be very negligible. Hence, there are no external current limit resistors needed for such use-cases. When ISO7721 outputs are connected to a different kind of input other than CMOS or TTL, then you would have to use external current limit resistor to limit the current into or out of ISO7721 output.

    Please note that the internal source or sink resistor is going to be ~50Ω. Please consider this value into account while designing external current limit. Thanks.

    Koteshwar Rao