SLVS074I January 1983 – July 2022 TL494
The design of the TL494 not only incorporates the primary building blocks required to control a switching power supply, but also addresses many basic problems and reduces the amount of additional circuitry required in the total design. The TL494 is a fixed-frequency pulse-width-modulation (PWM) control circuit. Modulation of output pulses is accomplished by comparing the sawtooth waveform created by the internal oscillator on the timing capacitor (CT) to either of two control signals. The output stage is enabled during the time when the sawtooth voltage is greater than the voltage control signals. As the control signal increases, the time during which the sawtooth input is greater decreases; therefore, the output pulse duration decreases. A pulse-steering flip-flop alternately directs the modulated pulse to each of the two output transistors. For more information on the operation of the TL494, see the application notes located on ti.com.