SNVSCU3 October   2025 LM5137

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Related Products
  6. 5 Pin Configuration and Functions
    1. 5.1 Wettable Flanks
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Input Voltage Range (VIN)
      2. 7.3.2  Bias Supply Regulator (VCC, BIAS1/VOUT1, VDDA)
      3. 7.3.3  Precision Enable (EN1, EN2)
      4. 7.3.4  Switching Frequency (RT)
      5. 7.3.5  Pulse Frequency Modulation and Synchronization (PFM/SYNC)
      6. 7.3.6  Synchronization Out (SYNCOUT)
      7. 7.3.7  Dual Random Spread Spectrum (DRSS)
      8. 7.3.8  Configurable Soft Start (RSS)
      9. 7.3.9  Output Voltage Setpoints (FB1, FB2)
      10. 7.3.10 Error Amplifier and PWM Comparator (FB1, FB2, COMP1, COMP2)
        1. 7.3.10.1 Slope Compensation
      11. 7.3.11 Inductor Current Sense (ISNS1+, BIAS1/VOUT1, ISNS2+, VOUT2)
        1. 7.3.11.1 Shunt Current Sensing
        2. 7.3.11.2 Inductor DCR Current Sensing
      12. 7.3.12 Minimum Controllable On-Time
      13. 7.3.13 100% Duty Cycle Capability
      14. 7.3.14 MOSFET Gate Drivers (HO1, HO2, LO1, LO2)
      15. 7.3.15 Output Configurations (CNFG)
        1. 7.3.15.1 Independent Dual-Output Operation
        2. 7.3.15.2 Single-Output Interleaved Operation
        3. 7.3.15.3 Single-Output Multiphase Operation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Sleep Mode
      2. 7.4.2 PFM Mode
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Power Train Components
        1. 8.1.1.1 Power MOSFETs
        2. 8.1.1.2 Buck Inductor
        3. 8.1.1.3 Output Capacitors
        4. 8.1.1.4 Input Capacitors
        5. 8.1.1.5 EMI Filter
      2. 8.1.2 Error Amplifier and Compensation
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1 – Dual 5V and 3.3V, 20A Buck Regulator for 12V Input Applications
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2 Custom Design With Excel Quickstart Tool
          3. 8.2.1.2.3 Inductor Calculations
          4. 8.2.1.2.4 Shunt Resistors
          5. 8.2.1.2.5 Ceramic Output Capacitors
          6. 8.2.1.2.6 Ceramic Input Capacitors
          7. 8.2.1.2.7 Feedback Resistors
          8. 8.2.1.2.8 Input Voltage UVLO Resistors
          9. 8.2.1.2.9 Compensation Components
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Design 2 – Two-Phase, Single-Output Synchronous Buck Regulator
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
      3. 8.2.3 Design 3 – 12V, 20A, 400kHz, Two-Phase Buck Regulator for 48V Server Applications
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Power Stage Layout
        2. 8.4.1.2 Gate Drive Layout
        3. 8.4.1.3 PWM Controller Layout
        4. 8.4.1.4 Thermal Design and Layout
        5. 8.4.1.5 Ground Plane Design
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Development Support
        1. 9.1.2.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
        1. 9.2.1.1 Low-EMI Design Resources
        2. 9.2.1.2 Thermal Design Resources
        3. 9.2.1.3 PCB Layout Resources
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.2.2.1 Design Requirements

Table 8-6 shows the intended input, output, and performance parameters for this automotive circuit example.

Table 8-4 Design Parameters
DESIGN PARAMETERVALUE
Input voltage range (steady state)8V to 18V
Minimum transient input voltage 6V
Maximum transient input voltage 36V
Output voltage5V
Output current20A
Switching frequency2.1MHz
Output voltage regulation±1%
No-load sleep current with phase 2 disabled< 20µA
Shutdown current4µA

Resistor RRT of 10.5kΩ sets the switching frequency at 2.1MHz. In terms of control loop performance, the target loop crossover frequency is 80kHz with a phase margin greater than 50°. Leaving the RSS pin open sets the output voltage soft-start time to 6.5ms.

Table 8-7 cites the selected buck regulator powertrain components, with many of the components available from multiple vendors. Similar to circuit example 1, this design uses 40V logic-level MOSFETs, shielded buck inductors, shunt resistors with wide aspect ratio for low ESL, and an all-ceramic input and output capacitor implementation.

Table 8-5 List of Materials for Application Circuit 2
REFERENCE DESIGNATORQTYSPECIFICATION(1)MANUFACTURERPART NUMBER
CIN1, CIN2410µF, 50V, X7R, 1210, ceramicTDKCNA6P1X7R1H106K
10µF, 50V, X7S, 1210, ceramicMurataGCM32EC71H106KA03
TDKCGA6P3X7S1H106M
COUT1, COUT2847µF, 6.3V, X7R, 1210, ceramicMurataGCM32ER70J476KE19L
Taiyo YudenJMK325B7476KMHTR
47µF, 6.3V, X7S, 1210, ceramicTDKCGA6P1X7S0J476M
LO1, LO220.47µH, 2.2mΩ, 26.5A, 6.71 × 6.51 × 3.1mmCoilcraftXGL6030-471MEC
0.47µH, 3mΩ, 25A, 6.95 × 6.6 × 4.3mmCyntecVCUW064ER47MS5
0.47µH, 3.1mΩ, 20A, 7 × 6.9 × 3.8mmWürth Electronik744311047
0.56µH, 3mΩ, 29A, 6.6 × 6.4 × 2.8mmBournsSRP6030CA-R56M
Q1, Q3240V, 4.7mΩ, 7nC, SON 5 × 6InfineonIAUC60N04S6L039ATMA
Q2, Q4 2 40V, 3.6mΩ, 9nC, SON 5 × 6 Infineon IAUCN04S7L028ATMA
RS1, RS22Shunt, 4mΩ ±1%, ±50ppm/°C, 0612, 1.5WSusumuKRL3216E-C-R004-F
U11LM5137 80V two-phase synchronous buck controllerTexas InstrumentsLM5137RHAR
(1) See Third-Party Products Disclaimer.