MAXREFDES39# Analog Devices

MAXREFDES39 : POWER AMPLIFIER BIASING THROUGH MAX11300 PIXI IC MAXREFDES39 System Board Introduction The MAXREFDES39 power amplifier (PA) bias reference design uses the MAX11300, also called a programmable mixed-signal I/O (PIXI IC), to bias and monitor a power amplifier for an RF base station application. In this case, an Infineon PTMA210152M-20W is used but any Power Amplifier can be used. The MAX11300 provides a highly integrated solution for the RF power amplifier biasing infrastructure. The design utilizes all of the MAX11300s analog peripherals, while only requiring one MAX11300 device to both bias and monitor a 2-stage RF power amp. All the features of this reference design are listed below. Monitor, biasing, and control for frequency division duplex (FDD) and time division duplex (TDD) radio frequency (RF) power amplifiers. Monitoring function o Accurate voltage and current measurement o Current measurement through Maxim current-sense amplifier (MAX44285) o Drain voltage and current of first- and second-stage amplifiers o Two external and one internal temperature monitors o Gate biasing of first-stage and second-stage amplifiers Control function o Fast RF PA on/off o Synchronized TDD function o Efficient, adjustable drain voltage supply o LED signaling and alarm o Automatic control function Figure 1, The MAXREFDES39 system block diagram The USB interface to the microcontroller and serial interface to the MAX11300 are digitally isolated from the main circuit through the MAX14850. The microcontroller section is powered through USB power, whereas the rest of the circuit is powered by a separate 36V DC supply. Figure 1 also shows power control and monitoring for RF PA.