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ISO7721: Input Clamping Diode Max Current

Stuart Baker
Genius 10270 points
Part Number: ISO7721

I'm working with an application that has a higher than VCCI input voltage of up to 24V (VCCI is 5V). I am using a large external series resistor to limit the current and relying on the internal clamping diodes to clamp the input to VCCI.

In order to appropriately size the external series resistor, what is the clamping current rating of the internal clamping diodes?

Thanks,

Stuart

  • 0
    TI__Mastermind 49435 points

    Hi Stuart,

    Thanks for reaching out to us. The bypass diodes that you see at input pins are the ESD and their primary function is to handle HBM ESD of ±6kV as stated in the datasheet. They are only rated to handle a fine set of HBM pulses that last a few 10s of nano-seconds and are not rated for continuous operation. This is the reason the input pin has an absolute max spec of VCCI+0.5V. Applying any voltage higher than VCCI+0.5V could lead to device damage over a period of time and/or affect device reliability.

    Hence, I suggest to use others external means to bring this voltage down before applying it to input pins of ISO7721. Examples include using a voltage divider, using a voltage divider and a buffer, using a voltage translator among others.

    I hope this answers your question, thanks.

    Regards,
    Koteshwar Rao