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LMC555: VCTL variation of temperature

Yasushi Fujiwara
Genius 12725 points

Part Number: LMC555
Other Parts Discussed in Thread: TLC555

Hi Experts,

My customer is now designing 30s+/-15% timer by LMC555. Customer has concern about variation by temperature or something. Would you answer for a following questions? (The supply voltage will be 5V.)
1. How much variation does VCTRL has by temperature?
2. To achieve less than 15% variation by Ta=-40~+85decC, what is important a design point of view? external components variation, capacitor type or anything?
3. Please let me know if you have any notes to achieve less than 15% variation at 30s timer.

Your support would be much appreciated.
Best Regards,
Fujiwara

  • 0
    TI__Guru**** 171636 points

    Fujiwara-san

    I have some sample data for control voltage for TLC555 timer and it is very stable. I will find or take new data for LMC555 timer control voltage versus temperature today.

  • 0 in reply to Ron Michallick
    TI__Guru**** 171636 points

    Fujiwara-san,

    Here is the control voltage versus temperature sample data for LMC555 and TLC555 timers at 5V supply

    Data is expressed as a percentage of the 5V supply. 

    Timing capacitors should have low leakage, low temperature drift, low voltage modulation, tight tolerances. These capacitor types could be used; mylar, polycarbonate, polystyrene, tantalum.

    Resistors should be tight tolerance and low temperature drift. The charge current should be set significantly higher than the total expected leakage current in the application (timer + cap + board).

    Because the timer voltage drops a little with temperature, a small positive resistor drift could be helpful.