8.3.7 PWM Generator

Maximum duty cycle is higher for these devices than for their UC384x predecessors. This is primarily due to the higher ratio of timing capacitor discharge-to-charge current, which can exceed one hundred-to-one in a typical BiCMOS application. Attempts to program the oscillator maximum duty cycle much below the specified range, by adjusting the timing component values of R_T and C_T, must be avoided. There are two reasons to refrain from this design practice. First, the device's high discharge current would necessitate higher charging current than necessary for programming, defeating the purpose of low power operation. Second, a low-value timing resistor may prevent the capacitor from discharging to the lower threshold and initiating the next switching cycle.