pwm/vfm step-down dc/dc controller general description the pt1101 series are cmos-based pwm step-down dc/dc controllers with low supply current. a low ripple, high efficiency step-down dc/dc converter can be easily composed of with additional several external components such as a power-transistor, an inductor, a diode and capacitors. output voltage is fixed or can be adjusted with external resisters. (pwm/vfm alternative circuit is disabled in adjustable types)

the pt1101 series consist of a pwm control circuit, a high precision band-gap voltage reference, a soft-start circuit, a protection circuit, a pwm/vfm alternative circuit, an oscillator, an error amplifier with internal compensation network and input/output voltage detection circuits.

with its internal state-of-art control algorithm, the pt1101 series based dc/dc converter can achieve high performance while maintaining stability. for example, with its pwm/vfm alternative circuit, when the load current is small, the operation is automatically switched into the vfm mode to improve the efficiency. further, if the term of maximum duty cycle keeps on a certain time, the embedded protection circuits restart the operation with soft-start and repeat until the maximum duty cycle condition is released. finally, built-in uvlo function blocks potentially unstable output when the input voltage is equal or less than uvlo threshold and makes this ic standby for low power consumption.