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# ISOW7841: Over-voltage protection

Part Number: ISOW7841

Hi,

Referring to AN SLLA440 about over-voltage protection (http://www.ti.com/lit/an/slla440/slla440.pdf, the resistor values are ok for given example UVTP=1.94V (equation 1). However, if the same resistor values are used in Equation 2, the calculated OVTP=5.18V (much lower than stated OVTP=5.82V in Table 1). What is correct (resistor values or Equation 2).

If VISO=3.3V, which values do you suggest for UVTP and OVTP?

Thanks,

Goran

• Hi Goran,

I see that you had also posted the same question on another similar post. I am copying below my response for completeness.

Thank you for reporting the error in calculated values from the equations and data in Table 1. The value of OVTP was calculated assuming VISO value of 6V which yields the OVTP to be as 5.82V. I see that the table lists VISO as 5V, I apologize for this error.

I have slightly modified the OVTP equation to make it independent of VISO so that UVTP and OVTP values can be calculating using only the resistor and VREF values. Please find below the updated equations and two example tables showing resistor values for 5V and 3.3V outputs. I will also get the document SLLA440 updated accordingly. Let me know if you have any questions.

Thanks again. Regards,
Koteshwar Rao

• In reply to Koteshwar Rao:

Hi Goran,

I am also including below a calculator that you can use to adjust the values and play around further if needed. Thanks.

UVTP, OVTOP Calculator.xlsx

Regards,
Koteshwar Rao

• In reply to Koteshwar Rao:

Thank you very much Koteshwar!

Your help and support is exceptional and I appreciate it greatly!

Kind regards,

Goran