LMS3655 Synchronous Step-Down Converters

By Texas Instruments 66

LMS3655 Synchronous Step-Down Converters

Texas Instruments' 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 24 V to an output of 3.3 V at a fixed frequency of 400 kHz 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.

Features
  • 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

Applications

  • Noise-sensitive medical applications
  • Telecom
  • High performance industrial 
  • 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 (typ.)
  • 32 µA IQ_VIN: quiescent current at 3.3 VOUT and no load (typ.)
  • 5.5 A continuous load current
  • Adjustable output voltage (1 V to 15 V)
  • ±1.5% reference voltage tolerance
  • 4 mm x 5 mm, 0.5 mm pitch SON package

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