Need a pull-up on the SE555D?

Louis S

Other Parts Discussed in Thread: SE555

According to the datasheet (http://www.ti.com/lit/ds/symlink/se555.pdf), the 555 series can source or sink 200 mA. However, the example operation diagrams show R_L (1K seems recommended) across VCC and OUT. Is this only for the sake of generating the typical waveforms? With a 15 V power supply, I'd prefer not to burn 1/4 W whenever the output is low. I believe I can remove this pull-up resistor, but wanted to make sure I'm not doing anything that will have impacts on the reliability/longevity of the design.

Thanks,

Louis

over 11 years ago

0 Arvind Sridhar over 11 years ago

TI__Mastermind 24205 points

Hi Louis,

I have forwarded your request to the applications team responsible for this product support. You should hear back from them soon.

Regards

Arvind Sridhar

0 Louis S over 11 years ago in reply to Arvind Sridhar

Intellectual 325 points

I removed R_L from my design, and the output had no significant change (maybe a 0.1 V shift downwards, but I think my ground may not be great). I'd just like to confirm I'm not over-stressing the timer by removing this.

0 Ron Michallick over 11 years ago

TI__Guru**** 166906 points

Louis,

No resistor is needed. When used, it improves VOH when the output load is light.
You may omit the resistor without any concern.

0 Louis S over 11 years ago in reply to Ron Michallick

Intellectual 325 points

Got it, thanks!

Clock & timing

Clock & timing forum

Need a pull-up on the SE555D?