Hello,

I have a question about internal resistor value of R1 and R2.

I will pull-up SENSER1 pin to 3.3V by 10k ohms. I would like to check the impact of the external resistor value (10k ohms). Could you please advise me the resistor value of R1 and R2?

Best regards,

Akira

Hi Okasaka-san,

This is what design had to say:

Confirming the following resistor values (roughly in line with estimate based on the data sheet specs):

R1 = 955kohms

R2 = 246kohms

The ratio of these two resistors will stay constant, and expected to match to within better than 1%.

The absolute values of the resistors will change with temperature. The resistor values will decrease as temp goes up, maybe by as much as 15% from 25degC to 85degC.

The absolute value of the resistors will also change from part to part, so an allowance for +/-25% at least.

If the user is adding a 10kohm resistor externally, the impact is that it will move the nominal threshold up by ~1%. Allowing for this being in the range of 0.5% to 1.5% though, to account for the mismatch of this external resistor to the absolute value of the internal resistors.