NE556 Maximum speed and minimum pulse width

Jim McNamara

We need to know minimum values for Ra & Rb, the maximum oscillator frequency and the minimum pulse width for output and minimum pulse width for input. Device is powered from 15 VDC. Cap. "C" is .001uf .

Circuit is in production for many years operating at about 42Khz and a 1us pulse width. Prior parts were Signetics and ST

over 9 years ago

0 Arvind Sridhar over 9 years ago

TI__Mastermind 24205 points

Hi Jim,

I have forwarded your query to the applications engineer most familiar with this device. Expect a reply soon.

Regards

Arvind Sridhar

0 Jim McNamara over 9 years ago in reply to Arvind Sridhar

Prodigy 20 points

I have not heard an answer from Ti Engineering about the question.
We will need to make a production decision soon.
Thank you.
Jim

0 Ron Michallick over 9 years ago in reply to Jim McNamara

TI__Guru**** 165826 points

Jim,

In a-stable mode, up to 100kHz is supported, however the data sheet formula becomes inaccurate for high frequencies.
I suggest his equation for choosing resistor and capacitors; (2RB+RA)*C = 1.44 / [ F * (1+F/350 kHz)

In mono-stable mode, minimum output pulse width is 10uS. There is no stated minimum input width, it will be less the delay seen in figure 8 of data sheet (less than 1uS).

At 15V VCC, the discharge pin can also support 200mA to allow for low RA and RB values.

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NE556 Maximum speed and minimum pulse width