SLFS043I September 1983 – July 2019 TLC555
The operation of the timer can be modified by modulating the internal threshold and trigger voltages, which is accomplished by applying an external voltage (or current) to CONT. Figure 20 shows a circuit for pulse-width modulation. A continuous input pulse train triggers the monostable circuit, and a control signal modulates the threshold voltage. Figure 21 shows the resulting duty cycle versus control voltage transfer function. Attempting to run under 10% duty cycle could result in inconsistent output pulses. Attempting to run close to 100% duty cycle will result in frequency division by 2, then 3, then 4.