Nujira (United Kingdom)

Power management of mobile digital systems-on-chip necessitates large voltage regulation performances. DC/DC converters used to supply digital cores are facing stringent constraints with respect to load transients, reference tracking and accuracy. The fast transient response offered by sliding-mode control is well suited to DC/DC converters with fast varying load. Fixed switching-frequency is also mandatory for EMI and noise related issues. Fixed-switching frequency sliding-mode control has been experimented as a multi-loop system. There is a necessity to investigate the stability when multi-loops interact and the parameter set for each loop is quite large. The paper details a methodology for the stability analysis of a frequency-controlled sliding-mode DC/DC converter. The proposed stability analysis takes the possible cross-interactions into account and can be used to optimise the DC/DC controller without the limitations of a non-interaction criterion. As a verification a DC/DC converter is implemented in CMOS 130 nm. Experimental results agree with the analysis main recommendations.

This letter presents a signal probability distribution
\nfunction conscious characterization technique, suitable for the
\noptimization of envelope tracking (ET) power amplifiers. The
\nmethod and its validation rely on pulsed harmonic load-pull measurements. The analytical treatment permitted to understand the impact of the peak-to-average power ratio on the load termination, and the experimental characterization revealed the sensitivity of the ET performance with respect to the load termination. The technique was applied to a GaN HEMT device at the carrier frequency of 870 MHz.