2.7MHz, 2.5A Step-Down DC-DC Converter with Analog Bypass Mode for 2G/3G/4G PAs - LM3243


2.7MHz, 2.5A Step-Down DC-DC Converter with Analog Bypass Mode for 2G/3G/4G PAs


The LM3243 is a DC-DC converter optimized for powering multi-mode 2G/3G/4G RF power amplifiers (PAs) from a single Lithium-Ion cell. The LM3243 steps down an input voltage from 2.7V to 5.5V to a dynamically adjustable output voltage of 0.4V to 3.6V. 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 efficiency.

The LM3243 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 to 1.4A (typ.) while still driving a 2.5A load. The ACB also enables operation with minimal dropout voltage. The LM3243 is available in a small 2 mm x 2 mm chip-scale 16-bump DSBGA package.

If you are considering using the LM3243 in a system design, please see the PCB Layout Considerations section of this data sheet.


  • High-Efficiency PFM and PWM modes with
    Internal Synchronous Rectification
  • Analog Bypass Function with Low
    Dropout Resistance (45 mΩ typ.)
  • Dynamically Adjustable Output Voltage, 0.4V to
    3.6V (typ.), in PFM and PWM Modes
  • 2.5A Maximum Load Current in PWM Mode
  • 2.7 MHz (average) PWM Switching Frequency
  • Modulated switching frequency to aid Rx Band Compliance
  • Operates from a Single Li-ion Cell (2.7V to 5.5V)
  • ACB reduces inductor requirements and size
  • Minimum total solution size by using small footprint and case size
    inductor and capacitors
  • 16-bump thin DSBGA Package
  • Current and Thermal Overload Protection

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Parametrics Compare all products in RF DC/DC Converter

Vin (Min) (V)
Vin (Max) (V)
Vout (Min) (V)
Vout (Max) (V)
Iout (Max) (A)
Switching Frequency (Typ) (kHz)
Special Features
Operating Temperature Range (C)
Approx. Price (US$)
LM3243 LM3263 LM3279
2.7     2.7     2.7    
5.5     5.5     5.5    
0.4     0.4     0.4    
3.6     3.6     4.2    
2.5     2.5     1    
Buck     Buck     Buck-Boost    
ACB     ACB      
2700     2700     2400    
Adjustable Output
Light Load Mode    
Adjustable Output
Light Load Mode
MIPI RFFE Interface    
Adjustable Output
Light Load Mode
MIPI RFFE Interface
Sleep/Standby Mode    
-30 to 90     -30 to 90     -30 to 85    
16DSBGA     16DSBGA     16DSBGA    
0.45 | 1ku     0.48 | 1ku     0.75 | 1ku    

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