The LM3248 is a PWM/PFM Boost-Buck DC/DC converter that provides efficient utilization of battery
power over a wide voltage range. The device architecture is suitable for advanced RF front-end
systems that demand dynamic voltage and current to support converged power amplifier architectures
operating in 2G/3G/4G and 3GPP/LTE modes. For example, the LM3248 is designed to produce higher
output voltages while maintaining PFM mode as
required by some new reduced-power CMOS PAs.
The extremely fast Boost-Buck function reduces RF
PA overhead power dissipation, extending battery talk time. The device will operate at input voltage VIN
range of 2.7V to 5.5V and an adjustable output
voltage VOUT range of 0.4V to 4.0V at a maximum
current load of 2.5A.
The LM3248 is available in a 30-bump, lead-free thin
The LM3248 utilizes step-up (Boost) and variable output step-down (Buck) DC/DC converters. Combining a
cascaded Boost and Buck converter in a single package is ideal for powering the latest multimode/multi-standard
RF power amplifiers. The Boost converter provides the RF power subsystem the capability to operate at lower
battery voltages as well as to maintain increased PA linearity and transmit power margins over a wider battery
voltage supply range.
The Buck has a unique Active Current assist and analog Bypass (ACB) feature to minimize inductor size without
any loss of output regulation for the entire battery voltage and RF output power range, until dropout. ACB
provides a parallel current path, when needed, to limit the maximum inductor current while still driving a 2.5A
load. The LM3248 may also be configured as a Buck-only converter with a boost bypass feature to enable
highest efficiency operation with minimal dropout voltage when the Boost is not needed.
The LM3248 automatically and seamlessly transitions between Pulse Width Modulation (PWM) and Pulse
Frequency Modulation (PFM) modes for high-efficiency operation with both full and light load conditions.
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