Hi TI,
The LM555CN timer works based on the following linear relationship: F = 1/T = 1/(C*(R1+2R2)*ln(2)). I just wonder what the linearity range of this relationship is? In other words, what is the maximum and minimum capacitance and resistor values that allow the above equation to hold.
Sincerely,
Khoi Ly
Khio,
That formula works well for frequencies below 10 kHz. Above that will result in an error that increases with frequency mostly due to propagation delay from timing cap (1/3, 2/3 Vcc) to discharge output changing state.
This formula and text from TLC551 data sheet is more accurate / informative. Ron = discharge pin on resistance.
Khio,
I start with this simplified equation for NE555 or LM555 astable timers to pick initial resistors and capacitor values.
For application above 80 kHz or those that need more accuracy, I suggest TLC555, LMC555 (or TLC551).
