This paper presents an all-digital current-sensorless multi-mode DC-DC converter for portable applications. All-digital load current detector, operation mode detector and multi-mode controller are implemented. The multi-mode controller can seamlessly change modes between pulse frequency modulation (PFM) and pulse width modulation (PWM) with the aid of load current detector and operation mode detector. The cooperation of PWM and PFM can maintain good output voltage regulation and light-load efficiency over wide load range. The digital controller, power MOSFET and driver are fabricated in TSMC 90-nm standard CMOS process. The experimental results show that the proposed architecture can achieve high efficiency over a wide load range.