The ADP2138 and ADP2139 are high efficiency, low quiescent current, synchronous step-down dc-to-dc converters. The ADP2139 has the additional feature of an internal discharge switch. The total solution requires only three tiny external components.
When the MODE pin is set high, the buck regulator operates in forced PWM mode, which provides low peak-to-peak ripple for power supply noise sensitive loads at the expense of light load efficiency. When the MODE pin is set low, the buck regulator automatically switches operating modes, depending on the load current level. At higher output loads, the buck regulator operates in PWM mode. When the load current falls below a predefined threshold, the regulator operates in power save mode (PSM), improving light load efficiency.
The 3 MHz switching frequency minimizes the size of external components.