Envelope-tracking DC/DC converter supports 3G and 4G LTE bands

October 08, 2013 // By Paul Buckley
Texas Instruments is claiming the industry’s most efficient envelope tracking power supply solution to support 3G and 4G LTE multi-mode, multi-band RF power amplifiers used in smartphones and tablets.

The LM3290 step-down converter has been developed to extract more life out of a battery by using an integrated DC boost and companion LM3291 linear amplifier to enable the use of envelope tracking techniques in RF transmitters to reduce the power amplifier temperature by 20C and reduce overall power consumption by 25%, compared to systems that use average power tracking.

LTE signals need a high peak-to-average ratio (PAR), and generate higher transmit power, which reduces the efficiency of RF power amplifiers and creates extra heat. The LM3290 and LM3291, which support battery voltages down to 2.5V, provide high efficiency at higher power output levels and high PAR, while meeting stringent receive band noise requirements in all LTE bands.

The LM3290 and LM3291 devices manage all 3G and 4G LTE bandwidths up to 20 MHz and battery voltages from 2.5V to 5V; supports requirements for major suppliers’ power amplifiers. The devices’ envelope tracking capability helps reduce heat and power consumption by as much as 25% and achieves greater than 90% efficiency.

Smartphones and tablets do not need to depend on maximum power reduction when battery power is low. The integrated DC boost converter in the LM3290 provides maximum transmit power – supporting higher LTE data rates even at lower battery voltage levels.

The devices support the MIPI eTrak analogue differential front end interface for envelope tracking and a 1.8-V MIPI RFFE digital interface to simplify integration with RF platforms. The devices also allow seamless transition between envelope tracking and average power tracking operating modes.

The LM3290 and LM3291 support a minimum bandwidth of 75 MHz - an industry-first when using envelope tracking, TI says - providing high accuracy with excellent adjacent channel leakage ratio and noise performance.

The LM3290 buck-boost converter comes in a 30-bump, DSBGA package, and is priced at $0.80 (1,000). The LM3291 linear amplifier comes in a 12-bump DSBGA package, and is priced at $0.75.

Texas Instruments; www.ti.com/lm3290-pr-eu