SNVS615K January   2010  – February 2018 LM27402

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Performance Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Wide Input Voltage Range
      2. 7.3.2  UVLO
      3. 7.3.3  Precision Enable
      4. 7.3.4  Soft-Start and Voltage Tracking
      5. 7.3.5  Output Voltage Setpoint and Accuracy
      6. 7.3.6  Voltage-Mode Control
      7. 7.3.7  Power Good
      8. 7.3.8  Inductor-DCR-Based Overcurrent Protection
      9. 7.3.9  Current Sensing
      10. 7.3.10 Power MOSFET Gate Drivers
      11. 7.3.11 Pre-Bias Start-up
    4. 7.4 Device Functional Modes
      1. 7.4.1 Fault Conditions
        1. 7.4.1.1 Thermal Protection
        2. 7.4.1.2 Current Limit
        3. 7.4.1.3 Negative Current Limit
        4. 7.4.1.4 Undervoltage Threshold (UVT)
        5. 7.4.1.5 Overvoltage Threshold (OVT)
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Converter Design
      2. 8.1.2  Inductor Selection (L)
      3. 8.1.3  Output Capacitor Selection (COUT)
      4. 8.1.4  Input Capacitor Selection (CIN)
      5. 8.1.5  Using Precision Enable
      6. 8.1.6  Setting the Soft-Start Time
      7. 8.1.7  Tracking
      8. 8.1.8  Setting the Switching Frequency
      9. 8.1.9  Setting the Current Limit Threshold
      10. 8.1.10 Control Loop Compensation
      11. 8.1.11 MOSFET Gate Drivers
      12. 8.1.12 Power Loss and Efficiency Calculations
        1. 8.1.12.1 Power MOSFETs
        2. 8.1.12.2 High-Side Power MOSFET
        3. 8.1.12.3 Low-Side Power MOSFET
        4. 8.1.12.4 Gate-Charge Loss
        5. 8.1.12.5 Input and Output Capacitor ESR Losses
        6. 8.1.12.6 Inductor Losses
        7. 8.1.12.7 Controller Losses
        8. 8.1.12.8 Overall Efficiency
    2. 8.2 Typical Applications
      1. 8.2.1 Example Circuit 1
        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
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Example Circuit 2
      3. 8.2.3 Example Circuit 3
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Power Stage Layout
      2. 10.1.2 Gate Drive Layout
      3. 10.1.3 Controller Layout
      4. 10.1.4 Thermal Design and Layout
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.1.2.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the LM27402 device with the WEBENCH® Power Designer.

  1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
  2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
  3. Compare the generated design with other possible solutions from Texas Instruments.

The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability.

In most cases, these actions are available:

  • Run electrical simulations to see important waveforms and circuit performance
  • Run thermal simulations to understand board thermal performance
  • Export customized schematic and layout into popular CAD formats
  • Print PDF reports for the design, and share the design with colleagues

Get more information about WEBENCH tools at www.ti.com/WEBENCH.

The current limit setpoint in this design is set at 25 A at 25°C, based on resistor RSET and the inductor DCR of 2.34 mΩ. Of course, the current limit setpoint must always be selected such that the operating current level does not exceed the saturation current specification of the chosen inductor. The component values for the DCR sense network (RS and CS in Figure 41) are chosen based on setting the RSCS product approximately equal to L/RDCR, as recommended in the Setting the Current Limit Threshold section. The MOSFETs are chosen for both lowest conduction and switching power loss, as discussed in detail in the Power MOSFETs section.

Table 1. Bill of Materials

DESIGNATORTYPEPARAMETERSPART NUMBERQTYMANUFACTURER
U1 IC Synchronous Buck Voltage-Mode PWM Controller LM27402 1 TI
CBOOT Capacitor 0.22 µF, Ceramic, X7R, 25 V, 10% GRM188R71E224KA88D 1 Murata
CC1 Capacitor 3.9 nF, Ceramic, X7R, 50 V, 10% GRM188R71H392KA01D 1 Murata
CC2 Capacitor 150 pF, Ceramic, C0G, 50 V, 5% GRM1885C1H151JA01D 1 Murata
CC3 Capacitor 820 pF, Ceramic, C0G, 50 V, 5% GRM1885C1H821JA01D 1 Murata
CVDD Capacitor 1 µF, Ceramic, X5R, 25 V, 10% GRM188R61E105KA12D 1 Murata
CF Capacitor 1 µF, Ceramic, X5R, 25 V, 10% GRM188R61E105KA12D 1 Murata
CIN Capacitor 22 µF, Ceramic, X5R, 25 V, 10% GRM32ER61E226KE15L 5 Murata
COUT Capacitor 100 µF, Ceramic, X5R, 6.3 V, 20% C1210C107M9PACTU 4 Kemet
CS Capacitor 0.22 µF, Ceramic, X7R, 25 V, 10% GRM188R71E224KA88D 1 Murata
CSS Capacitor 47 nF, Ceramic, X7R, 16 V, 10% GRM188R71C473KA01D 1 Murata
CSBY Capacitor 100 pF, Ceramic, C0G, 50 V, 5% GRM1885C1H101JA01D 1 Murata
DBOOT Diode Schottky Diode, Average I = 100 mA, Max Surge I = 750 mA CMOSH-3 1 Central Semi
DSW Diode Schottky Diode, Average I = 3A, Max Surge I = 80A CMSH3-40M 1 Central Semi
LOUT Inductor 0.68 µH, 2.34 mΩ IHLP5050CEERR68M06 1 Vishay
QL N-CH MOSFET 30 V, 60 A, 43.5 nC, RDS(on) at 4.5 V = 1.85 mΩ Si7192DP 1 Vishay
QH N-CH MOSFET 25 V, 40 A, 13 nC, RDS(on) at 4.5 V = 6.2 mΩ SiR436DP 1 Vishay
RC1 Resistor 8.06 kΩ, 1%, 0.1 W CRCW06038k06FKEA 1 Vishay
RC2 Resistor 261 Ω, 1%, 0.1 W CRCW0603261RFKEA 1 Vishay
RFADJ Resistor 45.3 kΩ, 1%, 0.1 W CRCW060345K3FKEA 1 Vishay
RFB1 Resistor 20.0 kΩ, 1%, 0.1 W CRCW060320K0FKEA 1 Vishay
RFB2 Resistor 13.3 kΩ, 1%, 0.1 W CRCW060320K0FKEA 1 Vishay
RF Resistor 2.2 Ω, 5%, 0.1 W CRCW06032R20JNEA 1 Vishay
RPGD Resistor 51.1 kΩ, 5%, 0.1 W CRCW060351K1JNEA 1 Vishay
RS Resistor 1.3 kΩ, 1%, 0.1 W CRCW06031K30FKEA 1 Vishay
RSET Resistor 6.34 kΩ, 1%, 0.1 W CRCW06036K34FKEA 1 Vishay