NE555 astable frequency range

Peter Chen(ICP_FAE)

Intellectual 2480 points

Other Parts Discussed in Thread: NE555, LMC555, SE555, SA555, NA555

What is the NE555 frequency range in astable? Is there any RC design criteria for NE555 in astable condition design?

over 9 years ago

0 Ron Michallick over 9 years ago

TI__Guru**** 164706 points

Hello Peter,

The NE555 can run up to 100kHz . Above that is pretty iffy.
The data sheet formula is not very accurate above 10 kHz and is increasing bad on the way to 100 kHz
For example 14 kHz is DS formula error is 4% and 60 kHz is a 17% formula error

Here is a better formula to pick the timing components.
I added a fudge factor based on typical empirical data.
(2*RB+RA)*C = 1.44 / [ F * (1+F/350 kHz) ]

F is the desired frequency in Hz. RB and RA are in ohms, and C in farads.

0 Peter Chen(ICP_FAE) over 8 years ago in reply to Ron Michallick

TI__Intellectual 2480 points

Ron,
I try both formula in LMC555 astable is not matching. I put the parameters figure2 of LMC555 datasheet, the maxium frequency is not matching to datasheet describe(3Mhz in astable mode). Is there anything i miss?

0 Ron Michallick over 8 years ago in reply to Peter Chen(ICP_FAE)

TI__Guru**** 164706 points

Peter,

My formula is only for NE555, NA555, SE555, and SA555.

LMC555 is a different design.

0 Ron Michallick over 8 years ago in reply to Ron Michallick

TI__Guru**** 164706 points

Perter,

For LMC555 questions, start a new post.

Clock & timing

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NE555 astable frequency range