A 1-A 6-MHz Digitally Assisted Buck–Boost Converter With Seamless Mode Transitions and Fast Dynamic Performance for Mobile Devices

A 1-A 6-MHz buck-boost converter with seamless mode transitions and fast dynamic operation is proposed for extending the useable voltage range of Li-ion batteries in mobile devices, and thereby their battery life. The proposed converter employs a proportional-integral peak-current-mode pulsewidth modulation controller with a digital adaptive slew-rate control scheme that minimizes output undershoots, overshoots, and settling time during mode transitions and dynamic events, such as load and output voltage steps. Additionally, hysteretic mode detection is proposed to prevent falsely triggering the converter to transition between the various operation modes (i.e., buck, boost, and buck-boost) and negatively impacting the performance of the circuit loads. The converter is fabricated in 0.13-μm CMOS technology, and supports 2.3-5 V input and 1.5-3.6 V output. The converter achieves 91.7% peak efficiency and over 80% efficiency at 1-mA load across all conditions. The output voltage ripple is less than 10 mV with a 220-nH inductor and a 10-μF output capacitor.