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TLC555: Bypass Capacitor, TLC555 vs SA555

Motoyasu Hattori
Genius 10025 points
Part Number: TLC555
Other Parts Discussed in Thread: SA555, LM555, LMC555

Hi,

My customer uses TLC555IDR, instead of SA555DR.

*1. According to datasheet of SA555, A bypass capacitor is highly recommended from VCC to ground pin; ceramic 0.1 µF capacitor is sufficient.  In other hands, on the TLC555 datasheet, Minimum recommended is 0.1-μF ceramic in parallel with 1-μF electrolytic.

Why is different?
Is the noise immunity of TLC555IDR weakened when comparing the bipolar IC and the Cmos IC?

*2. On 1uF electrolytic capacitor on TLC555, What characteristics do you need in a capacitor?

*3. Regarding the type of capacitor of TLC555, is it possible to use other than electrolytic capacitors?

Please advise us.

Thanks and best regards,
M.HATTORI

  • 0
    TI__Mastermind 36388 points

    Hello Hattori-san,

    It's unlikely that the noise immunity of the parts is any different, unless the data sheet specifically says so. The LM555 (bipolar) and LMC555 (cmos) both recommend 0.1-μF ceramic in parallel with 1-μF electrolytic, so I do not think it is a bipolar vs cmos comparison. The SA555 datasheet was released 10 years before the TLC555. It never hurts to have more bypass capacitance, especially nowadays when capacitors are cheaper and smaller, so I believe the newer datasheets recommend having the two capacitors for this reason. The datasheet is just a general recommendation, but you should add bypass capacitors dependent on the types of noise you expect the board to see. 

    You do not have to use an electrolytic capacitor for the 1-μF. I believe this is also an older recommendation when larger ceramic capacitors were not as common. 

    Best,

    Katlynne Jones