1FEATURES
23• Highly Programmable High-Current Linear
Amplifier
• > 75 MHz Typical Small Signal Bandwidth
• Extremely Low Output Impedance
• High Linearity
• Differential Analog Input Compatible with
eTrak 1.0 Standard
• Low Output Noise
• When paired with the LM3290 provides a
complete Envelope Modulator solution for
3G/4G Envelope Tracking Power Amplifiers.
• Automatically controlled through LM3290 in an
envelope modulation solution using MIPI®
RFFE 1.1-compatible interface.

APPLICATIONS
• 3G/LTE Handsets
• 3G//LTE Tablets
• 3G/LTE Data Cards and Wireless Modems

DESCRIPTION
The LM3291 is a high-speed linear amplifier that, with
its companion IC LM3290, constitutes an RF
Envelope Modulator (EM) for supplying 3G/4G Power
Amplifiers (PA) in envelope tracking systems. The
amplifier provides extremely low output impedance
and low output noise over a wide bandwidth.
In conjunction with an Envelope Tracking (ET)
capable RFIC and PA, the LM3291 and LM3290
greatly improve PA efficiency for 3G and LTE operation.
In ET mode, the LM3291 and LM3290 provide
envelope tracking supply voltage for the PA maximizing total EM + PA efficiency. The envelope
modulator follows the differential envelope reference
input signal delivered by the RFIC to the LM3291.
The output is a single-ended dynamic power supply
voltage to the PA.
The LM3291 supports 3G and LTE operation up to 20
MHz signal bandwidth.
The LM3291’s programmable parameters are
controlled by LM3290 via a direct serial interface
between the two devices. No additional controls are
needed in the system. This interface provides flexible
control and adjustment options to optimize LM3291
efficiency and noise performance for various
frequency bands and power levels.
At high TX output power, the EM can be operated in
ET mode where LM3290 and LM3291 together
modulate the supply of the PA with the envelope
signal to improve overall system efficiency. At low TX
output power, the EM can be transitioned to Average
Power Tracking (APT) mode where LM3291 is placed
into shutdown mode to improve system efficiency.
The LM3291 is available in a 12-pin lead-free DSBGA
package.
For the full datasheet, samples, or the EVM
hardware and software please contact a TI
representative at ET@list.ti.com.