SNVSCU2A August   2024  – August 2024 LM5137-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  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 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. 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 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 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

8.2.1.1 Design Requirements

Table 8-2 shows the intended input, output, and performance parameters for this automotive circuit example.

Table 8-2 Design Parameters
DESIGN PARAMETER VALUE
Input voltage range (steady state) 6.5V to 36V, nominal 13.5V
Minimum transient input voltage (cold crank) 4.5V
Maximum transient input voltage (load dump) 36V
Output voltages 5V, 3.3V
Output currents (EDC)(1) 20A
Output currents (TDC)(1) 15A
Switching frequency 440kHz
Target efficiency at 5V, 15A 96%
Target efficiency at 3.3V, 15A 94.5%
Output voltage regulation ±1%
Loop crossover frequency 60kHz
Phase margin > 45°
No-load sleep current, channel 2 disabled < 20µA
Shutdown current 4µA
(1) EDC and TDC refer to electrical and thermal design currents, respectively.

Resistor RRT sets the switching frequency at 440kHz. In terms of control loop performance, the target loop crossover frequency is set in the range of 10% to 15% of switching frequency – 60kHz in this example – with a target phase margin greater than 45°. Connecting a resistance of 20kΩ at RSS sets the output voltage soft-start times to 4.6ms.

Table 8-3 cites the selected buck regulator powertrain components, with many of the components available from multiple vendors. Section 8.1.1.1 describes selection of power MOSFETs for lowest conduction and switching power loss. This application circuit uses 40V logic-level MOSFETs, metal-alloy buck inductors with low DCR, low-ESL shunts, and ceramic input and output capacitors – all AEC qualified.

Table 8-3 List of Materials for Application Circuit 1
REFERENCE DESIGNATOR QTY SPECIFICATION(1) MANUFACTURER PART NUMBER
CIN1, CIN2 8 10µF, 50V, X7R, 1210, ceramic, AEC-Q200 TDK CNA6P1X7R1H106K
10µF, 50V, X7S, 1210, ceramic, AEC-Q200 Murata GCM32EC71H106K
TDK CGA6P3X7S1H106K
COUT1, COUT2 8 47µF, 10V, X7S, 1210, ceramic, AEC-Q200 TDK CNA6P1X7S1A476M
Murata GCM32EC71A476K
LO1, LO2 2 1µH, 2.3mΩ, 37A, 10.85 × 10 × 5.2mm, AEC-Q200 Cyntec VCHA105D-1R0MS6
1µH, 2.3mΩ, 37A, 11 × 10 × 5.1mm, AEC-Q200 Bourns SRP1050WA-1R0M
1µH, 2.1mΩ, 24A, 10.8 × 10 × 5mm, AEC-Q200 Eaton HCM1A1105V2-1R0-R
1µH, 2.7mΩ, 33.8A, 10.85 × 10 × 3.8mm, AEC-Q200 Würth Electronik 784373680010
1µH, 2.4mΩ, 36.6A, 10.5 × 10 × 6.5mm, AEC-Q200 TDK SPM10065VT-1R0M-D
Q1, Q3 2 40V, 3.6mΩ, 9nC, SON 5 × 6, AEC-Q101 Infineon IAUCN04S7L028ATMA1
Q2, Q4 2 40V, 2.4mΩ, 15nC, SON 5 × 6, AEC-Q101 Infineon IAUCN04S7L019ATMA1
RS1, RS2 2 Shunt, 2mΩ ±2%, ±100ppm/°C, 1225, 3W, AEC-Q200 Susumu KRL6432E-M-R002-G
U1 1 LM5137-Q1 80V dual-channel buck controller, AEC-Q100 Texas Instruments LM5137QRHARQ1
(1) See the Third-Party Products Disclaimer.