Selecting DC-DC Step-Down Voltage Regulators For WiFi RF Power Amplifier Applications

By David Brown, Skyworks Solutions, Inc.

Wireless local area network (WLAN) radio frequency (RF) links have been integrated into almost all facets of portable and mobile products today. Operating in 802.11ac requires greater RF power amplifier (PA) linearity compared to legacy 802.11a/b/g/n systems which, in many cases, has reduced the RF PA input supply voltage range while drawing more input current with increased power dissipation demands.

New 802.11ac RF PAs often pose a challenge to portable product designers, because the RF PA input supply range is no longer compatible with direct connection to a Li-Ion/poly battery supply voltage range. This means that a voltage regulator must now be employed. Performance for an 802.11ac RF PA can be affected by the voltage regulator operation, but regulator integration can be simplified if the designer knows which key performance characteristics to evaluate in a DC-DC step-down voltage regulator. An additional benefit of a DC-DC switching voltage regulator is reduced system power dissipation, which reduces the WLAN circuit thermal footprint and saves power drawn from the battery source supply. Many very small footprint DC-DC voltage regulators are available today to fit the need of the 802.11ac WiFi PA application.