SNVSCU2B August   2024  – August 2025 LM5137-Q1

PRODUCTION DATA  

  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 Automotive Battery 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 for Automotive ADAS Applications
        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 Automotive 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

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.9 Output Voltage Setpoints (FB1, FB2)

The LM5137-Q1 can be independently configured for one of the three fixed output voltage setpoints or adjusted to the desired output voltage using an external resistor divider. As shown in Table 7-2, configure VOUT1 or VOUT2 for a 3.3V, 5V, or 12V voltage setpoint by connecting the respective FB pin with a 7.5kΩ, 24.9kΩ, or 48.7kΩ to VDDA, respectively.

Table 7-2 Feedback Configuration Resistor
PULLUP RESISTOR TO VDDA VOUT SETPOINT
7.5kΩ 3.3V
24.9kΩ 5V
48.7kΩ 12V
Not installed External FB divider setting

The configuration settings are latched and cannot be changed until the LM5137-Q1 is powered down with the VCC voltage decreasing below the falling UVLO threshold, and then powered up again with VCC above 3.8V.

Alternatively, set the output voltage with an external resistor divider from the output to AGND. The FB regulation voltage is 0.8V, and the output voltage setpoint range is from 0.8V to 60V. Use Equation 4 to calculate the upper and lower feedback resistors, designated RFB1 and RFB2, respectively. See Figure 7-4.

Equation 4. LM5137-Q1

A recommended starting value for RFB2 is between 10kΩ and 20kΩ.

LM5137-Q1 Voltage Loop With Adjustable Output Setting Figure 7-4 Voltage Loop With Adjustable Output Setting

If high light-load efficiency is required, take care when selecting the external resistors. The current consumption of the external divider adds to the LM5137-Q1 sleep current. The divider current reflected to VIN scales by the ratio of VOUT/VIN.