5.5A, 36V Synchronous, 400kHz, Step-Down Converter - LMS3655


5.5A, 36V Synchronous, 400kHz, Step-Down Converter



The LMS3655 synchronous buck regulators are optimized for high performance applications, providing an adjustable output of 1 V to 15 V. Seamless transition between PWM and PFM modes, along with a low quiescent current, ensures high efficiency and superior transient responses at all loads.

Advanced high speed circuitry allows the LMS3655 to regulate an input of 24V to an output of 3.3V at a fixed frequency of 400kHz while also enabling a continuous load current of 5.5 A. An innovative frequency foldback architecture allows this device to regulate a 3.3-V output from an input voltage of only 3.5 V. The input voltage can range up to 36 V, with transient tolerance up to 42 V, easing input surge protection design.

An open-drain reset output, with built-in filtering and delay, provides a true indication of system status. This feature negates the requirement for an additional supervisory component, saving cost and board space.


  • 96% Peak Efficiency While Converting 12 V to 5 V
  • Low EMI and Switch Noise
    • Minimized Switch Node Ringing
    • Pseudo-Random Spread Spectrum
  • 400-kHz (±10%) Fixed Switching Frequency
  • –40°C to +150°C Junction Temperature Range
  • External Frequency Synchronization
  • RESET Output With Internal Filter and 3-ms Release Timer
  • Automatic Light Load Mode for Improved Efficiency
  • Pin-Selectable Forced PWM Mode
  • Built-In Compensation, Soft Start, Current Limit, Thermal Shutdown, and UVLO
  • 0.35-V Dropout With 3.5-A Load at 25°C (Typical)
  • 32-µA IQ_VIN: Quiescent Current at 3.3 VOUT and No Load (Typical)
  • 5.5-A Continuous Load Current
  • Adjustable Output Voltage (1 V to 15 V)
  • ±1.5% Reference Voltage Tolerance
  • 4-mm × 5-mm, 0.5-mm Pitch SON Package

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Parametrics Compare all products in Buck Converter (Integrated Switch)

Vin (Min) (V)
Vin (Max) (V)
Vout (Min) (V)
Vout (Max) (V)
Iout (Max) (A)
Regulated Outputs (#)
Switching Frequency (Min) (kHz)
Switching Frequency (Max) (kHz)
Iq (Typ) (mA)
Special Features
Control Mode
Duty Cycle (Max) (%)
Operating Temperature Range (C)
Package Group
Frequency Synchronization
Light Load Efficiency
Power Good
Pre-Bias Start-Up
Synchronous Rectification   
Current Mode   
-40 to 125   

WEBENCH® Designer LMS3655

  Min   Max Range
Vin  V 3.8 to 36.0V
Product Option
Vout  V 3.3 to 15.0V
Iout  A ≤ 0.20 to 5.5A
Ambient Temp  °C -40 to 125°C