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  • TI Thinks Resolved

NE555: CMOS or TTL?

Prodigy 160 points

Replies: 16

Views: 1312

Part Number: NE555

At present, when using ne555 to drive MOS behind the small power LED, using switching power supply, ne555 works normally, put on the battery (lithium battery / carbonic acid) battery voltage test 13.5v. This time has been powered and the battery voltage will be down to 1v, off Turn on the battery voltage measurement, or 13,5v, disconnect the battery on the foot, the battery voltage is normal, please help confirm what is the reason Is ne555 CMOS or ttl? When reading 5v input, it is written as ttl level. Please help confirm whether the wide voltage input is cmos. Is the internal integrated transistor just ttl level? Both power modes are normal using tlc555

  • In reply to user4173409:

    The first pulse can be longer because the timing capacitor normally starts from 0V and the second pulse (In a-stable mode) starts at 33% of VCC. Pulses can be shorter before the capacitor on pin 5 has fully charged. Can you share your 555 timer circuit?

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Ron Michallick:

    How much is the capacitance of 5 PIN?

  • In reply to user4173409:

    It is negligible, probably close to 4pF. Normally there is an external capacitor that sets the capacitance on pin 5.
    If a couple picofarads matter then the application frequency is far too high for the NE/NA/SE/SA/LM555 timers.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Ron Michallick:

    I can help better, If I knew the components around the timer and if the timer is set up for monostable or a-stable mode.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Ron Michallick:

    Frequency is 75K.
  • In reply to user4173409:

    75kHz is close to the maximum frequency of NE/NA/SE/SA/LM555 timers. They will run up to 100 kHz however the higher the frequency the more the device to device variance. Above 25 kHz, the simplified frequency formula in the data sheet increases in error because propagation delay becomes a factor which is not included in the formula because that would make it too complex. TLC555 and LMC555 timer have less propagation delay and less varinece at 75 kHz.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

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