LMC555: Duty ratio variation

Kazuya-san,

Duty cycle variance is usually more accurate than frequency because the values of the capacitor and internal propagation delay do not matter.

The resistor value tolerance will be the dominate factor unless the resistors used are too low and the discharge on resistance becomes a factor.

If the FA frequency is very high then changes in the spacing between rising and falling propagation delays will also become  factor.

What are the Ra, Rb, and C values used?

Ron,

Thank you very much for your reply.
The customer is using same circuit as Figure 15 on page 15 in LMC555 datasheet (SNAS558M).
Also R/C values are the follows.
RA=1kohm(+/-1%), RB=15kohm(+/-1%) and C=430pF(+/-5%).

Could you please give me any comment base on the conditions?

Thank you again and best regards,
Kazuya Nakai.