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TLC555: minimum duty cycle

David Park
Expert 6810 points
Part Number: TLC555
Other Parts Discussed in Thread: TIDA-01183

Hi,

TLC555 has to be designed for 4% or 3% duty cycle.

Accuracy at 4% or 3% duty cycle is same as one over 5%?

If it is worse, can below TIDA improve it?

Thanks.

  • 0
    TI__Guru**** 166706 points
    David,

    For 3% in the TIDA-01183, I would suggest changing R2 (in the timer circuit) from 39k to 68k so that the CONT pin voltage can stay greater than 1V.
    R8 and R9 also need to be changed so that the tap voltage changes from 250mV to 150mV (3%) or 200mV (4%)

    From a ground up design that doesn't use a servo to run the CONT pin voltage then change R1 and R2 to get a natural 3% or 4% from the TLC555 timer with a undriven CONT pin (just use the standard cap to GND on CONT pin). The diode is a temperature problem for accurate duty cycle. This can be fixed by remove the diode and setting R1 and R2 for 97% or 96% duty cycle then invert the output.