A Monolithic 3-Level Single-Inductor Multiple-Output Buck Converter with State-Based Non-Linear Control Capable of Handling 1A/1.5ns Transient with On-Die LC

Abstract

3-Level Single-Inductor Multiple-Output (SIMO) buck converter is introduced in [1] to provide multiple outputs sharing one inductor to save cost while taking advantage of 3-Level topologies. Linear voltage-mode PWM control was used in [1], which is also what most single-output 3-Level converters used. It is intuitive to generate matching duty-cycles (D1 and D2) for the 2 pairs of switches by having the error amplifier (EA) outputs cutting interleaved ramps. However, linear control has small-signal bandwidth limitation, which is even more challenging to optimize with multiple dependent loops in SIMO and 3-Level converters. This is further compromised to ensure stability with PVT/component/loading variations. In the literature of SIMO converters [1]-[7], load-transient response was typically limited to handle steps: :;250 mA to avoid excessive droops due to self-/cross-regulation. Faster control loops can help correct voltage errors in time to reduce droops and support a faster and larger load transient for advanced digital loads. Non-linear control such as hysteretic control was widely used in buck converters for a faster response. However, it is not intuitive to generate switching signals to non-linearly control a 3-Level SIMO converter.