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  • LM5149 80-V, Synchronous, Buck, DC/DC Controller with Ultra-Low IQ and Integrated Active EMI Filter

    • SNVSBV4A December   2020  – January 2023 LM5149

      PRODUCTION DATA  

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  • LM5149 80-V, Synchronous, Buck, DC/DC Controller with Ultra-Low IQ and Integrated Active EMI Filter
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Active EMI Filter
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Input Voltage Range (VIN)
      2. 8.3.2  High-Voltage Bias Supply Regulator (VCC, VCCX, VDDA)
      3. 8.3.3  Precision Enable (EN)
      4. 8.3.4  Power-Good Monitor (PG)
      5. 8.3.5  Switching Frequency (RT)
      6. 8.3.6  Active EMI Filter
      7. 8.3.7  Dual Random Spread Spectrum (DRSS)
      8. 8.3.8  Soft Start
      9. 8.3.9  Output Voltage Setpoint (FB)
      10. 8.3.10 Minimum Controllable On Time
      11. 8.3.11 Error Amplifier and PWM Comparator (FB, EXTCOMP)
      12. 8.3.12 Slope Compensation
      13. 8.3.13 Inductor Current Sense (ISNS+, VOUT)
        1. 8.3.13.1 Shunt Current Sensing
        2. 8.3.13.2 Inductor DCR Current Sensing
      14. 8.3.14 Hiccup Mode Current Limiting
      15. 8.3.15 High-Side and Low-Side Gate Drivers (HO, LO)
      16. 8.3.16 Output Configurations (CNFG)
      17. 8.3.17 Single-Output Dual-Phase Operation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Sleep Mode
      2. 8.4.2 Pulse Frequency Modulation and Synchronization (PFM/SYNC)
      3. 8.4.3 Thermal Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Power Train Components
        1. 9.1.1.1 Buck Inductor
        2. 9.1.1.2 Output Capacitors
        3. 9.1.1.3 Input Capacitors
        4. 9.1.1.4 Power MOSFETs
        5. 9.1.1.5 EMI Filter
        6. 9.1.1.6 Active EMI Filter
      2. 9.1.2 Error Amplifier and Compensation
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 – High-Efficiency 2.1-MHz Synchronous Buck Regulator
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2 Custom Design With Excel Quickstart Tool
          3. 9.2.1.2.3 Buck Inductor
          4. 9.2.1.2.4 Current-Sense Resistance
          5. 9.2.1.2.5 Output Capacitors
          6. 9.2.1.2.6 Input Capacitors
          7. 9.2.1.2.7 Frequency Set Resistor
          8. 9.2.1.2.8 Feedback Resistors
          9. 9.2.1.2.9 Compensation Components
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Design 2 – High Efficiency 48-V to 12-V 400-kHz Synchronous Buck Regulator
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Design 3 – High Efficiency 440-kHz Synchronous Buck Regulator
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
        3. 9.2.3.3 Application Curves
      4. 9.2.4 Design 4 – Dual-Phase 400-kHz 20-A Synchronous Buck Regulator
        1. 9.2.4.1 Design Requirements
        2. 9.2.4.2 Detailed Design Procedure
        3. 9.2.4.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 Power Stage Layout
        2. 9.4.1.2 Gate-Drive Layout
        3. 9.4.1.3 PWM Controller Layout
        4. 9.4.1.4 Active EMI Layout
        5. 9.4.1.5 Thermal Design and Layout
        6. 9.4.1.6 Ground Plane Design
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
        1. 10.1.1.1 Custom Design With WEBENCH® Tools
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
        1. 10.2.1.1 PCB Layout Resources
        2. 10.2.1.2 Thermal Design Resources
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information
  12. IMPORTANT NOTICE

Package Options

Mechanical Data (Package|Pins)
  • RGY|24
    • MPQF143E
Thermal pad, mechanical data (Package|Pins)
  • RGY|24
    • QFND678
Orderable Information
  • snvsbv4a_oa
  • snvsbv4a_pm
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DATA SHEET

LM5149 80-V, Synchronous, Buck, DC/DC Controller with Ultra-Low IQ and Integrated Active EMI Filter

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.

Package Information
PART NUMBER PACKAGE(1) BODY SIZE (NOM)
LM5149 RGY (VQFN, 24) 3.50 mm × 5.50 mm
(1) For all available packages, see the orderable addendum at the end of the data sheet
Typical Application Schematic
GUID-0286B8E0-413D-4C32-BC0A-825537CAB271-low.gifCISPR 25 EMI Performance - 150 kHz to 30 MHz

4 Revision History

Changes from Revision * (December 2020) to Revision A (January 2023)

  • Changed document status from Advance Information to Production DataGo
  • Updated PFM/SYNC pin descriptionGo
  • Added TPC curvesGo
  • Updated Overview sectionGo
  • Updated the Functional Block Diagram Go
  • Changed 470-nF to 100-nFGo
  • Changed "spectrum analyzer" to "EMI receiver"Go
  • Added "where both outputs are tied together"Go
  • Updated PFM function mode descriptionGo
  • Updated PFM/SYNC descriptionGo
  • Changed "store" to "storage"Go
  • Changed "filter compensation" and "input compensation" to "compensation"Go
  • Added Design 1 - High Efficiency 2.1-MHz Buck Regulator sectionGo
  • Changed soft-start timeGo
  • Updated Table 9-4 Go
  • Updated title of Figure 9-10 Go
  • Added Design 2 - High Efficiency 48-V to 12-V 400-kHz Synchronous Buck Regulator sectionGo
  • Added Design 3 – High Efficiency 440-kHz Synchronous Buck Regulator sectionGo
  • Added Design 4 – Dual-Phase 400-kHz 20-A Synchronous Buck Regulator sectionGo
  • Updated Layout imageGo

5 Description (continued)

Additional features of the LM5149 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 and bootstrap diode, internal 3-ms soft-start time, and thermal shutdown protection with automatic recovery.

The LM5149- controller comes in a 3.5-mm × 5.5-mm thermally enhanced, 24-pin VQFN package with an exposed pad to aid in thermal dissapation.

6 Pin Configuration and Functions

Connect the exposed pad to AGND and PGND on the PCB.
Figure 6-1 24-Pin VQFN RGY Package(Top View)
Table 6-1 Pin Functions
PIN I/O(1) DESCRIPTION
NO. NAME
1 AVSS G Active EMI bias ground connection
2 INJ O Active EMI injection output
3 CNFG 1 Connect a resistor to ground to set primary/secondary, spread spectrum enable/disable, or interleaved operation. After start-up, use CNFG to enable AEF.
4 RT I Frequency programming pin. A resistor from RT to AGND sets the oscillator frequency between 100 kHz and 2.2 MHz.
5 EXTCOMP O The output of the transconductance error amplifier. If used, connect the compensation network from EXTCOMP to AGND.
6 FB I Connect FB to VDDA to set the output voltage to 3.3 V. Connect FB using a 24.9 kΩ or 49.9 kΩ to VDDA to set the output voltage to 5 V or 12 V, respectively. Install a resistor divider from VOUT to AGND to set the output voltage setpoint between 0.8 V and 55 V. The regulation voltage at FB is 0.8 V.
7 AGND G Analog ground connection. Ground return for the internal voltage reference and analog circuits.
8 VDDA O Internal analog bias regulator. Connect a ceramic decoupling capacitor from VDDA to AGND.
9 VCC P VCC bias supply pin. Connect ceramic capacitors between VCC and PGND.
10 PGND G Power ground connection pin for low-side power MOSEFT gate driver
11 LO O Low-side power MOSFET gate driver output
12 VIN P Supply voltage input source for the VCC regulators
13 HO O High-side power MOSFET gate driver output
14 SW P Switching node of the buck regulator and high-side gate driver return. Connect to the bootstrap capacitor, the source terminal of the high-side MOSFET, and the drain terminal of the low-side MOSFET.
15 CBOOT P High-side driver supply for bootstrap gate drive
16 VCCX P Optional input for an external bias supply. If VVCCX > 4.3 V, VCCX is internally connected to VCC and the internal VCC regulator is disabled.
17 PG/SYNCOUT P An open-collector output that goes low if VOUT is outside the specified regulation window. The PG/SYNCOUT pin of the primary controller in dual-phase mode provides a 180° phase-shifted SYNCOUT signal.
18 PFM/SYNC I Connect PFM/SYNC to VDDA to enable diode emulation mode. Connect PFM to GND to operate the LM5149 in forced PWM (FPWM) mode with continuous conduction at light loads. PFM/SYNC can also be used as a synchronization input to synchronize the internal oscillator to an external clock.
19 EN I An active-high precision input with rising threshold of 1 V and hysteresis current of 10 µA. If the EN voltage is less than 0.5 V, the LM5149 is in shutdown mode, unless a SYNC signal is present on PFM/SYNC.
20 ISNS+ I Current sense amplifier input. Connect the ISNS+ to the inductor side of the external current sense resistor (or to the relevant sense capacitor terminal if inductor DCR current sensing is used) using a Kelvin connection.
21 VOUT I Output voltage sense and the current sense amplifier input. Connect VOUT to the output side of the current sense resistor (or to the relevant sense capacitor terminal if inductor DCR current sensing is used).
22 AEFVDDA P Active EMI bias power. Connect a ceramic capacitor between AEFVDDA and AVSS.
23 SENSE I Active EMI sense input
24 REFAGND G Active EMI reference ground
(1) P = Power, G = Ground, I = Input, O = Output

 
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