The LM3243 is a DC-DC converter optimized for powering multi-mode 2G, 3G, and 4G RF power
amplifiers (PAs) from a single Lithium-Ion cell. The LM3243 steps down an input voltage from 2.7 V
to 5.5 V to a dynamically adjustable output voltage of 0.4 V to 3.6 V. The output voltage is set
through a VCON analog input that adjusts the output voltage to ensure efficient operation at all
power levels of the RF PA.
The LM3243 operates in constant frequency PWM mode producing a small and predictable
amount of output voltage ripple. This enables best ECTEL power requirements in GMSK and EDGE
spectral compliance, with the minimal amount of filtering and excess headroom. When operating in
PFM mode, the LM3243 enables the lowest DG09 current consumption and therefore maximizes system
The LM3243 has a unique ctive urrent assist and analog ypass (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 to 1.4 A (typical) while still driving a 2.5-A load.
The ACB also enables operation with minimal dropout voltage. When considering using the LM3243 in a
system design, see the Layout
section of this data sheet.
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