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 DSBGA package.
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.