1A, High Efficiency Dual Mode Single Inductor Buck-Boost DC/DC Converter

LM3668 is not recommended for new designs.
This product continues to be in production to support existing customers. Please consider one of the
Similar functionality to the compared device.
TPS63802 ACTIVE 2-A, high-efficient, 11-µA quiescent current buck-boost converter in QFN/DFN package The TPS63802 offers a smaller solution size, higher output current, a wider operating range and higher efficiency.

Product details

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  • 45-µA Typical Quiescent Current
  • For 2.8-V-3.3-V and 3-V-3.4-V Versions:
    • 1-A Maximum Load Current for
      VIN = 2.8 V to 5.5 V
    • 800-mA Maximum Load Current for
      VIN = 2.7 V
    • 600-mA Maximum Load Current for
      VIN = 2.5 V
  • For 4.5 V-5 V
    • 1-A Maximum Load Current for
      VIN = 3.9 V to 5.5 V
    • 800-mA Maximum Load Current for
      VIN = 3.4 V to 3.8 V
    • 700-mA Maximum Load Current for
      VIN = 3 V to 3.3 V
    • 600-mA Maximum Load Current for
      VIN = 2.7 V to 2.9 V
  • 2.2-MHz PWM Fixed Switching Frequency
    (Typical)
  • Automatic PFM-PWM Mode or Forced PWM
    Mode
  • Wide Input Voltage Range: 2.5 V to 5.5 V
  • Internal Synchronous Rectification for High
    Efficiency
  • Internal Soft Start: 600-µs Maximum Start-Up
    Time After VIN Settled
  • 0.01-µA Typical Shutdown Current
  • Current Overload and Thermal Shutdown
    Protection
  • Frequency Sync Pin: 1.6 MHz to 2.7 MHz
  • 45-µA Typical Quiescent Current
  • For 2.8-V-3.3-V and 3-V-3.4-V Versions:
    • 1-A Maximum Load Current for
      VIN = 2.8 V to 5.5 V
    • 800-mA Maximum Load Current for
      VIN = 2.7 V
    • 600-mA Maximum Load Current for
      VIN = 2.5 V
  • For 4.5 V-5 V
    • 1-A Maximum Load Current for
      VIN = 3.9 V to 5.5 V
    • 800-mA Maximum Load Current for
      VIN = 3.4 V to 3.8 V
    • 700-mA Maximum Load Current for
      VIN = 3 V to 3.3 V
    • 600-mA Maximum Load Current for
      VIN = 2.7 V to 2.9 V
  • 2.2-MHz PWM Fixed Switching Frequency
    (Typical)
  • Automatic PFM-PWM Mode or Forced PWM
    Mode
  • Wide Input Voltage Range: 2.5 V to 5.5 V
  • Internal Synchronous Rectification for High
    Efficiency
  • Internal Soft Start: 600-µs Maximum Start-Up
    Time After VIN Settled
  • 0.01-µA Typical Shutdown Current
  • Current Overload and Thermal Shutdown
    Protection
  • Frequency Sync Pin: 1.6 MHz to 2.7 MHz

The LM3668 is a synchronous buck-boost DC-DC converter optimized for powering low voltage circuits from a Li-Ion battery and input voltage rails between 2.5 V and 5.5 V. It has the capability to support up to 1-A output current over the output voltage range. The LM3668 regulates the output voltage over the complete input voltage range by automatically switching between buck or boost modes depending on the input voltage.

The LM3668 has 2 N-channel MOSFETS and 2 P-channel MOSFETS arranged in a topology that provides continuous operation through the buck and boost operating modes. There is a MODE pin that allows the user to choose between an intelligent automatic PFM-PWM mode operation and forced PWM operation. During PWM mode, a fixed-frequency 2.2 MHz (typical) is used. PWM mode drives load up to 1 A. Hysteretic PFM mode extends the battery life through reduction of the quiescent current to 45 µA (typical) at light loads during system standby. Internal synchronous rectification provides high efficiency. In shutdown mode (EN pin pulled low), the device turns off and reduces battery consumption to 0.01 µA (typical).

A high switching frequency of 2.2 MHz (typical) allows the use of tiny surface-mount components including a 2.2-µH inductor, a 10-µF input capacitor, and a 22-µF output capacitor.

The LM3668 is a synchronous buck-boost DC-DC converter optimized for powering low voltage circuits from a Li-Ion battery and input voltage rails between 2.5 V and 5.5 V. It has the capability to support up to 1-A output current over the output voltage range. The LM3668 regulates the output voltage over the complete input voltage range by automatically switching between buck or boost modes depending on the input voltage.

The LM3668 has 2 N-channel MOSFETS and 2 P-channel MOSFETS arranged in a topology that provides continuous operation through the buck and boost operating modes. There is a MODE pin that allows the user to choose between an intelligent automatic PFM-PWM mode operation and forced PWM operation. During PWM mode, a fixed-frequency 2.2 MHz (typical) is used. PWM mode drives load up to 1 A. Hysteretic PFM mode extends the battery life through reduction of the quiescent current to 45 µA (typical) at light loads during system standby. Internal synchronous rectification provides high efficiency. In shutdown mode (EN pin pulled low), the device turns off and reduces battery consumption to 0.01 µA (typical).

A high switching frequency of 2.2 MHz (typical) allows the use of tiny surface-mount components including a 2.2-µH inductor, a 10-µF input capacitor, and a 22-µF output capacitor.

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Technical documentation

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Type Title Date
* Data sheet LM3668 1-A, High-Efficiency Dual-Mode Single-Inductor Buck-Boost DC-DC Converter datasheet (Rev. O) PDF | HTML 23 Apr 2015
Application note Layer Design for Reducing Radiated EMI of DC to DC Buck-Boost Converters (Rev. A) PDF | HTML 09 Jun 2021
Selection guide Power Management Guide 2018 (Rev. R) 25 Jun 2018
EVM User's guide AN-1623 LM3668 Evaluation Board (Rev. F) 30 Apr 2013

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