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Original question:

UC1843A-EP: UC1843A-SP Oscillator frequency bend and temp. effect

UC1843A-EP: Datasheet curve showing Duty-Cycle vs RT value

Kenneth Aquino
Expert 1330 points
Part Number: UC1843A-EP

Tool/software:

Would you please tell me how the curve for Max Duty-Cycle vs Timing Resistor was derived?

I looked in Unitrode App Note U-111 and couldn't find that information.

Regards, 

Ken 

  • +1
    TI__Guru 73535 points

    Hi,

    Set up CT = 3.3nF, FB =0, ISESE=0, COMP = open, VREF with 0.1uF capacitor, VCC = 15V, measure CT saw tooth time between two peaks as T, and measure OUT = high time duration, tmax, then Dmax = tmax/T, along with RT change from 500-ohm to 100k-ohm.