1 Features
• Functional Safety-Capable
– Documentation available to aid functional safety
system design
• Two integrated EMI mitigation mechanisms
– Active EMI Filter for enhanced EMI
performance at lower frequencies
– Selectable dual random spread spectrum
(DRSS) for enhanced EMI performance across
low and high-frequency bands
– EMI reduced by an average of 25 dBμV
– Reduces the external differential-mode input
filter size by 50% and lowers systems cost
– Optimized for CISPR 32 Class B requirements
• Versatile synchronous buck DC/DC controller
– Wide input voltage range of 3.5 V to 80 V
– 1% accurate, fixed 3.3 V, 5 V, 12 V, or
adjustable output from 0.8 V to 55 V
– 150°C maximum junction temperature
– Shutdown mode current: 2.3 μA
– No-load sleep current: 9.5 μA
– Stackable up to two phases
– Advanced dropout with frequency foldback
• Switching frequency from 100 kHz to 2.2 MHz
– SYNC in and SYNC out capability
• Inherent protection features for robust design
– Internal hiccup-mode overcurrent protection
– ENABLE and PGOOD functions
– VCC, VDDA, and gate-drive UVLO protection
– Internal or external loop compensation
– Thermal shutdown protection with hysteresis
• Create a custom design using the LM5149 with
WEBENCH® Power Designer

2 Applications
• Building automation
• Industrial transport
• Wireless infrastucture
• Test and measurement

3 Description
The LM5149 is a 80-V, ultra-low IQ synchronous
buck DC/DC controller for high-current, single-output
applications. The controller uses a peak current-mode
control architecture for easy loop compensation,
fast transient response, and excellent load and line
regulation. The LM5149 can be set up in interleaved
dual-phase mode with accurate current sharing for
high-current applications. The device can operate with
VIN as low as 3.5 V, at nearly 100% duty cycle if
needed.
The LM5149 has two unique EMI reduction features:
active EMI filter and dual random spread spectrum
(DRSS). The active EMI filter senses any noise
or ripple voltage on the DC input bus and injects
an out-of-phase cancellation signal to reduce the
disturbance. DRSS combines low-frequency triangular
and high-frequency randomized modulations to
mitigate EMI across lower and higher frequency
bands, respectively. This hybrid technique aligns with
the multiple resolution bandwidth (RBW) settings
specified in industry-standard EMC tests.