SM72375_14 Datasheet, PDF (12/20 Pages) Texas Instruments – SM72375 SolarMagic Dual Micropower Rail-To-Rail Input CMOS Comparator with Open Drain Output

SM72375
SNIS155D – NOVEMBER 2010 – REVISED APRIL 2013
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A voltage divider of R₄ and R₅ establishes a reference voltage V₁ at the non-inverting input. By making the series
resistance of R₁ and R₂ equal to R₅, the comparator will switch when V_IN = 0. Diode D₁ insures that V₃ never
drops below −0.7V. The voltage divider of R₂ and R₃ then prevents V₂ from going below ground. A small amount
of hysteresis is setup to ensure rapid output voltage transitions.
OSCILLATOR
Figure 30. Square Wave Generator
Figure 30 shows the application of the SM72375 in a square wave generator circuit. The total hysteresis of the
loop is set by R₁, R₂ and R₃. R₄ and R₅ provide separate charge and discharge paths for the capacitor C. The
charge path is set through R₄ and D₁. So, the pulse width t₁ is determined by the RC time constant of R₄ and C.
Similarly, the discharge path for the capacitor is set by R₅ and D₂. Thus, the time t₂ between the pulses can be
changed by varying R₅, and the pulse width can be altered by R₄. The frequency of the output can be changed
by varying both R₄ and R₅.
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