42-V synchronous buck DC/DC controller with ultra-low IQ & integrated active EMI filter


Product details


Vin (Min) (V) 3.5 Vin (Max) (V) 42 Vout (Min) (V) 0.8 Vout (Max) (V) 36 Iout (Max) (A) 30 Iq (Typ) (uA) 9.5 Switching frequency (Min) (kHz) 100 Switching frequency (Max) (kHz) 2200 Features Adjustable Current Limit, Enable, Frequency Synchronization, Load Disconnect, Phase Interleaving, Power Good, Pre-Bias Start-Up, Spread Spectrum, Synchronous Rectification, UVLO Adjustable Operating temperature range (C) -40 to 150 Regulated outputs (#) 1 Number of phases 2 Rating Automotive open-in-new Find other Buck controllers (external switch)


  • Two integrated EMI mitigation mechanisms
    • Active EMI filter for enhanced EMI performance at lower frequencies
    • 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 filter size by 50% and lowers systems cost
  • Versatile synchronous buck DC/DC controller
    • Wide input voltage range of 3.5 V to 42 V
    • 1% accurate, fixed 3.3-V, 5-V, 12-V, or adjustable outputs from 0.8 V to 36 V
    • 150°C maximum junction temperature
    • Shutdown mode current: 2.2 µA
    • No-load standby current: 9 µA
  • 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 LM25149 with WEBENCH Power Designer
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The LM25149 is a 42-V synchronous buck DC/DC controller for high-current single-output applications. Refer to the Errata. The device uses peak current-mode control architecture for easy loop compensation, fast transient response, and excellent load and line regulation. The LM25149 can be set up in interleaved mode (paralleled output) with accurate current sharing for high-current applications. The LM25149 can operate at input voltages as low as 3.5 V, at nearly 100% duty cycle if needed.

The LM25149 has two unique EMI reduction features: active EMI Filter and Dual Random Spread Spectrum (DRSS). 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 noise or ripple voltage. DRSS combines a low-frequency triangular and high-frequency random modulation to optimize EMI preformance in the low-frequency and high-frequency radio frequency bands.

Additional features of the LM25149 include 150°C maximum junction temperature operation, user-selectable diode emulation for lower current consumption at light-load conditions, open-drain Power-Good flag for fault reporting and output monitoring, precision enable input, monotonic start-up into prebiased load, integrated VCC bias supply regulator, internal 2.8-ms soft-start time, and thermal shutdown protection with automatic recovery.

The LM25149 controller comes in a 3.5-mm × 5.5-mm thermally-enhanced, 24-pin VQFN package with wettable flank pins to facilitate optical inspection during manufacturing.

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NEW LM25149-Q1 PREVIEW 42-V automotive synchronous buck DC/DC controller with ultra-low IQ & integrated active EMI filter 42-VIN AEC-Q100-grade P2P option

Technical documentation

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Type Title Date
* Data sheet LM25149 42-V Synchronous Buck DC/DC Controller with Ultra-Low IQ and Integrated Active EMI Filter datasheet (Rev. A) Apr. 06, 2021
Technical article How to reduce EMI and shrink power-supply size with an integrated active EMI filter Apr. 05, 2021
User guide LM25149-Q1 EVM User's Guide Mar. 18, 2021
White paper Time-Saving and Cost-Effective Innovations for EMI Reduction Nov. 11, 2020

Design & development

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Hardware development

document-generic User guide
The LM25149-Q1EVM-2100 high-density evaluation module (EVM) is designed to showcase the performance of the LM25149-Q1 high-performance, automotive synchronous buck DC/DC buck controller. It operates over a wide input voltage range of 5.5 V to 36 V to deliver a fixed 5-V output with better than 1 (...)
  • 5.5-V to 36-V input voltage range
  • 5-V output voltage with 1% setpoint accuracy
  • Rated for 8 A of load current
  • Ultra-low IQ
  • Dual-random spread spectum and active EMI filtering for advance EMI mitigation
  • Fully assembled, tested and proven PCB layout with small footprint

Design tools & simulation

PSpice® for TI design and simulation tool
PSPICE-FOR-TI — PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
  • Leverages Cadence PSpice Technology
  • Preinstalled library with a suite of digital models to enable worst-case timing analysis
  • Dynamic updates ensure you have access to most current device models
  • Optimized for simulation speed without loss of accuracy
  • Supports simultaneous analysis of multiple products
  • (...)
LM5149 and LM25149 controller quickstart design tool
LM5149-LM25149DESIGN-CALC — Welcome to the quickstart design tool for the LM5149, LM5149-Q1 and LM25149, LM25149-Q1. This standalone tool facilitates and assists the power supply engineer with the design of a DC/DC buck regulator based on the above controller family. As such, the user can expeditiously arrive at an optimized (...)
  • Determine output filter inductance and input and output capacitances
  • Select components for input UVLO, OCP, output voltage setpoint and AEF
  • Optimize compensation values and pole/zero placement in terms of control loop stability using crossover frequency as a performance metric
  • Inspect regulator (...)
SNVR501.ZIP (1990 KB)

CAD/CAE symbols

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VQFN (RGY) 24 View options

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