SNVSCU2A August   2024  – August 2024 LM5137-Q1

ADVANCE INFORMATION  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1. 5.1 Wettable Flanks
  7. 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. 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 Minimum Controllable On-Time
      11. 7.3.11 Error Amplifier and PWM Comparator (FB1, FB2, COMP1, COMP2)
        1. 7.3.11.1 Slope Compensation
      12. 7.3.12 Inductor Current Sense (ISNS1+, BIAS1/VOUT1, ISNS2+, VOUT2)
        1. 7.3.12.1 Shunt Current Sensing
        2. 7.3.12.2 Inductor DCR Current Sensing
      13. 7.3.13 MOSFET Gate Drivers (HO1, HO2, LO1, LO2)
      14. 7.3.14 Output Configurations (CNFG)
        1. 7.3.14.1 Independent Dual-Output Operation
        2. 7.3.14.2 Single-Output Interleaved Operation
        3. 7.3.14.3 Single-Output Multiphase Operation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Sleep Mode
      2. 7.4.2 PFM Mode
  9. 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 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. 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 PCB Layout Resources
        2. 9.2.1.2 Thermal Design 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
    1. 11.1 Tape and Reel Information

Package Options

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

Gate Drive Layout

The LM5137-Q1 high-side and low-side gate drivers incorporate short propagation delays, adaptive deadtime control, and low-impedance output stages capable of delivering large peak currents with very fast rise and fall times to facilitate rapid turn-on and turnoff transitions of the power MOSFETs. Very high di/dt can cause unacceptable ringing if the trace lengths and impedances are not well controlled.

Minimization of stray or parasitic gate loop inductance is key to optimizing gate drive switching performance, whether it be series gate inductance that resonates with MOSFET gate capacitance or common source inductance (common to gate and power loops) that provides a negative feedback component opposing the gate drive command, thereby increasing MOSFET switching times. The following loops are important:

  • Loop 2: high-side MOSFET, Q1. During the high-side MOSFET turn-on, high current flows from the bootstrap (boot) capacitor through the gate driver and high-side MOSFET, and back to the negative terminal of the boot capacitor through the SW connection. Conversely, to turn off the high-side MOSFET, high current flows from the gate of the high-side MOSFET through the gate driver and SW, and back to the source of the high-side MOSFET through the SW trace. Refer to "loop 2" of Figure 8-25.
  • Loop 3: low-side MOSFET, Q2. During the low-side MOSFET turn-on, high current flows from the VCC decoupling capacitor through the gate driver and low-side MOSFET, and back to the negative terminal of the capacitor through ground. Conversely, to turn off the low-side MOSFET, high current flows from the gate of the low-side MOSFET through the gate driver and GND, and back to the source of the low-side MOSFET through ground. Refer to "loop 3" of Figure 8-25.

TI strongly recommends following circuit layout guidelines when designing with high-speed MOSFET gate drive circuits.

  • Connections from gate driver outputs, HO1/HO2 and LO1/LO2, to the respective gates of the high-side or low-side MOSFETs must be as short as possible to reduce series parasitic inductance. Be aware that peak gate drive currents can be as high as 3A. Use 0.65mm (25mils) or wider traces. Use via or vias, if necessary, of at least 0.5mm (20mils) diameter along these traces. Route the [HO1, SW1] and [HO2, SW2] gate traces as differential pairs from the LM5137-Q1 to the applicable high-side MOSFETs, taking advantage of flux cancellation.
  • Minimize the current loop path from the VCC and CBOOT1/CBOOT2 pins through the respective capacitors as these provide the high instantaneous current, up to 3A, to charge the MOSFET gate capacitances. Specifically, locate the bootstrap capacitors, CBST1 and CBST2, close to the respective [CBOOT1, SW1] and [CBOOT2, SW2] pin pairs of the LM5137-Q1 to minimize the areas of "loop 2" associated with the high-side drivers. Similarly, locate the VCC capacitor, CVCC, close to the VCC and PGND pins of the LM5137-Q1 to minimize the areas of "loop 3" associated with the low-side drivers.