Operating at a resistor-programmed fixed frequency between 100 kHz to 700 kHz, the device's adaptive constant-on-time control algorithm is capable of handling very wide input/output voltage ratios and helps reduce external component counts. The AP3591’s input and output voltage ranges are 4.5V to 26V and 0.75V to 5.5V respectively. Output current is up to 25A.
The controller enables the selection of two operating modes: a diode emulation mode that automatically reduces frequency and increases efficiency under light load conditions, and a constant-frequency, continuous-conduction mode that avoids light load output ripple.
Circuit protection features included in the 14-pin QFN3535 packaged controller include: resistor-programmable current limit, over-temperature shutdown, and over-voltage and under-voltage protection. The device also integrates both soft-start and soft-stop functions.
The AP3591 buck controller costs $0.33 (1000).