TLC555: What is the value of R in TLC555IDR,I want to use this value to calculate CONT Value

Hi Yan,

yx yan said:

What is the value of R in TLC555IDR,I want to use this value to calculate CONT Resistor Value.

Normally there should not be a resistor connected to CONT pin. A low esr bypass capacitor may be used to construct LPF filter and reduce noises and stable voltage for the signal comparisons, see pin5's description. I am unable to provide additional comments, since I do not know what you are trying to do. 

The video below is our latest recommendation how to implement bypass capacitor at the power rail. You are implementing old style bypass capacitors mythology. Please check the capacitor manufacture's recommendation and provide a better bypass coupling at the supply rail. 

https://www.youtube.com/watch?v=3rxKZWQk_DY

If you have other questions, please let us know. 

Best,

Raymond

I want to change the threshold of THRES and TRIG. So I want to know the value of R.

Thanks.

Hi Yan,

For Vdd =3Vdc, the current is approx. 250uA at 25C. This implies 3R = 3V/250uA ≈12kΩ or R ≈ 4kΩ.

These R values are temperature dependent, see the datasheet. So you need use low temperature coefficient resistor to parallel R767, and calculate the comparator voltage via voltage divider. 

If you have other questions, please let me know. 

Best,

Raymond