1 Features

1• 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 VOUT 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 IQ 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.