1 Features

• Wide Input Voltage Range of 3 V to 65 V
• 9.7-µA No-Load Quiescent Current
• –40°C to 150°C Junction Temperature Range
• Fixed (3.3-V, 5-V) or Adjustable V_OUT Options
• Meets EN55022 / CISPR 22 EMI Standards
• Integrated 1-Ω PFET Buck Switch
  • Supports 100% Duty Cycle for Low Dropout
• Integrated 0.5-Ω NFET Synchronous Rectifier
  • Eliminates External Schottky Diode
• Programmable Peak Current Limit Supports:
  • 500-mA, 300-mA, or 200-mA Loads
• Selectable PFM or COT Mode Operation
• 1.223-V ±1.2% Internal Voltage Reference
• Switching Frequency up to 600 kHz
• 900-µs Internal or Externally-Adjustable Soft Start
• Diode Emulation and Pulse Skipping for Ultra-High Light-Load Efficiency
• No Loop Compensation or Bootstrap Components
• Precision Enable and Input UVLO With Hysteresis
• Open-Drain Power Good Indicator
• Thermal Shutdown Protection With Hysteresis
• Pin-to-Pin Compatible With the LM5165
• 10-Pin, 3-mm × 3-mm VSON Package
• Create a Custom Regulator Design Using WEBENCH® Power Designer

2 Applications

• Factory and Building Automation
• Automotive and Battery-Powered Applications
• High Voltage LDO Replacement
• Low Power Bias Supplies

3 Description

The LM5166 is a compact, easy-to-use, 3-V to 65-V, ultra-low I_Q synchronous buck converter with high efficiency over wide input voltage and load current ranges. With integrated high-side and low-side power MOSFETs, up to 500 mA of output current can be delivered at fixed output voltages of 3.3 V or 5 V, or an adjustable output. The converter is designed to simplify implementation while providing options to optimize the performance for the target application. Pulse frequency modulation (PFM) mode is selected for optimal light-load efficiency or constant on-time (COT) control for nearly constant operating frequency. Both control schemes do not require loop compensation while providing excellent line and load transient response and short PWM on-time for large step-down conversion ratios.

The high-side P-channel MOSFET can operate at 100% duty cycle for lowest dropout voltage and does not require a bootstrap capacitor for gate drive. Also, the current limit setpoint is adjustable to optimize inductor selection for a particular load current requirement. Selectable and adjustable start-up timing options include minimum delay (no soft start), internally fixed (900 μs), and externally programmable soft start using a capacitor. An open-drain PGOOD indicator can be used for sequencing, fault reporting, and output voltage monitoring. The LM5166 is available in a 10-pin VSON package with 0.5-mm pin pitch.

1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical COT Mode Application

Typical COT Mode Application Efficiency