TLC555: Component value setting

Hello Eileen,

RA = 10k

RB = 133k

RD = 301 ohms

C = 10nF

Variance from full tolerance range.   

Hi Ron,

Thank you for your reply. If the freq is 400Hz, how to set them? The customer needs another PWM signal with 400Hz freq and 50% duty cycle, the other condition is the same.

Regards,

Eileen

Hi Ron,

What the precision requirements for the components? Are they listed in the first column of the table? If so, 0.1% tolerance resistors are not available in the customer's component library. Can they replace RB with 1% tolerance one?

Regards,

Eileen 

Eileen,

I have no requirements for precision. The main point of the table was to convey the point that output is about 500Hz and 50% 

1% resistors are fine. RB being 0.1% in table is point out that it is the most important resistor (of the three). 

The 5% for cap is to point that the capacitor is the main cause of output variance. It's tolerance, voltage and temperature modulations.    

Eileen,

The full FAQ is here:  [FAQ] How do I design a-stable timer, oscillator, circuits using LMC555, TLC555, LM555, NA555, NE555, SA555, or SE555? 

Frequency is inverse to resistors. They could factor the resistors by 500/400 = 1.25 the previous value 

RA 12.5k (12.4k) , Rb = 166.25k (165k), Rd = 376 (374 ohms)

Hi Ron,

Thank you for your reply. I'd like to confirm that, for 400Hz output, can we keep the RA=10K, but change RB to 174K?

Regards,

Eileen

Eileen,

[Ra, Rb, Rd] = [10k, 169k, 243] = 403Hz, 50.0% typical