problem with XR2206 calculations

Discussion in 'The Projects Forum' started by onlyvinod56, Apr 25, 2009.

  1. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    iam using HEF4752 for designing a PWm Inverter. (attachment 1)
    HEF4752 should be fed with four clock pulses FCT RCT VCT OCT.
    RCT & OCT both are fed with a common clock pulse.
    So finallly I need three pulse generators out of which one should be a VCO.

    I tried with CD4046. but i didnt get positive results. (attachment 2)
    i have some experience with XR2206. So i took three XR22006 ICs and started my work.

    from a journal (attachment 3), i got the info about HEF4752. The details are
    FCT = 3360 Fout
    VCT = 6720 Fout(max)
    RCT = OCT = 280 times max. switching freq.

    in my application the inverter output freq (Fout) from 5Hz to 50Hz.
    So FCT range should be
    3360*5 = 16800Hz = 16.8KHz
    3360*50 = 168000Hz = 168KHz

    My requirement is that FCT should be a VCO.
    A feedback sensor is ready to give a sweep voltage of 0 to -6V.
    The control voltage is varying from 0~6v (sweep) which has to produce a frequency ranging from 16.8KHz ~ 168KHz.

    See the URL. I have used R = 1K & Rc = 2K. What should be the capacitor value i have to use here. The practical readings are not matching with my theory.
    see the function generator chips at the bottom of the link

    I have one more problem. As iam generating higher frequencies such as 300KHz, The square wave shape is disturbing. One sharp corner is changing to a curve. If i still increased the frequency, the square pulse is changing to a spike.

    Help me with suitable components.