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TLC555 circuit

Saemyi Jeon
Intellectual 1110 points
Other Parts Discussed in Thread: DRV10866, TLC555, NE555

Hi all,

When I was looking at the user's guide of DRV10866, I cound find that the schematic circuit of TLC555(page 8) is different with the circuit of datasheet.

I didn't understand why output pin connects to variable resistor and how to operate the circuit.

would you explain what is the different between two circuits?

Thank you.

 

Best regards,

Sammy Jeon.

  • 0
    TI__Guru* 93105 points

    Hello Saemyi,

    The upper circuit from the TLC555 data sheet is for a fixed frequency, fixed duty cycle astable multivibrator (oscillator). It is the basic astable circuit and is usable for a duty cycle >= 50 %. The TLC555 data sheet applications information section provides some information about astable operation, but I think the NE555 data sheet explains it a little better:

    http://www.ti.com/lit/ds/symlink/ne555.pdf

    The lower TLC555 circuit is a variation on the astable multivibrator circuit. It is a fixed frequency multivibrator (25 kHz), but its duty cycle may be varied from 5 % to 95 % using the R2 potentiometer. The output of the TLC555 is fed back to the trigger input through R2 and the Schottky diodes, D1 and D2. R2 adjusts their forward currents affecting the ratio of the charge/discharge current. The trigger voltage is approximately 1.66 V. The duty cycle is dependent on how long the capacitor voltage remains above and below this level.

    Regards, Thomas

    PA - Linear Applications Engineering