A 93% Efficiency Delay Hysteretic Buck Converter With Ring Oscillator Based Frequency Synchronization and No-Load Operating <i>Iq</i> of 5.17 <i>μ</i>A

A current mode delay based hysteretic converter with a no load quiescent current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Iq</i>) of 5.17μA is presented. A ring oscillator-based delay generation method is proposed for creating the hysteresis window enabling easy implementation and integration into a frequency synchronization loop for constant switching frequency. The delay-based operation eliminates the need for a hysteretic comparator while generating the desired hysteresis window from the ring oscillator and path delay eliminating any errors in the operating frequency. The proposed converter operates at a constant switching frequency of 2.2MHz and supports a wide range of output capacitance from 20μF - 220μF. The controller supply is 1.8V and power gating for analog blocks reduces the static power dissipation in low power mode. The converter control and driver circuit is designed as an integrated circuit and is implemented in 180nm bipolar-CMOS-DMOS (BCD) technology and operates over a range of input voltage from 3.5V-5.5V generating an output voltage from 0.9V-2.4V. The converter can supply a max load current of 3A and achieves a peak efficiency of 93.01% and maintains efficiency above 70% across all load conditions.