1 Features
• Wide input voltage range of 3 V to 65 V
• 10.5-μA no-load quiescent current
• –40°C to 150°C junction temperature range
• Fixed (3.3 V and 5 V) or adjustable output voltages
• Meets EN55022 / CISPR 22 EMI standards
• Integrated 2-Ω PMOS buck switch
– Supports 100% duty cycle for low dropout
• Integrated 1-Ω NMOS synchronous rectifier
– Eliminates external rectifier diode
• Programmable current limit setpoint (four levels)
• Selectable PFM or COT mode operation
• 1.223-V ±1% internal voltage reference
• 900-μs internal or programmable soft start
• Active slew rate control for low EMI
• Diode emulation mode and pulse skipping for ultrahigh
light-load efficiency performance
• Monotonic start-up into prebiased output
• No loop compensation or bootstrap components
• Precision enable and input UVLO with hysteresis
• Pin-to-pin compatible with the LM5166
• Thermal shutdown protection with hysteresis
• 10-pin, 3-mm × 3-mm VSON package
• Use TPSM265R1 module for faster time to market
• Create a custom regulator design using
WEBENCH® Power Designer

2 Applications
• 4–20 mA loop-powered sensors
• Automotive and battery-powered equipment
• High-voltage LDO replacement
• Industrial control systems
• General-purpose bias supplies

3 Description
The LM5165 device 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 150-mA of output current
can be delivered at fixed output voltages of 3.3 V
or 5 V or at 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 output 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 LM5165 buck
converter is available in a 10-pin, 3-mm × 3-mm,
thermally- enhanced VSON-10 package with 0.5-mm
pin pitch. The LM5165 and LM5165X is also available
in the VSSOP-10 package.