SNVSCQ9 November   2025 LM68425-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Device Comparison Table
  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 Output Voltage Selection
      2. 7.3.2 EN Pin and Use as VIN UVLO
      3. 7.3.3 Mode Selection
        1. 7.3.3.1 MODE/SYNC/TEMP Pin Uses for Synchronization
        2. 7.3.3.2 Clock Locking
      4. 7.3.4 Adjustable Switching Frequency
      5. 7.3.5 Dual Random Spread Spectrum (DRSS)
      6. 7.3.6 Internal LDO, VCC UVLO, and BIAS Input
      7. 7.3.7 Bootstrap Voltage (BST Pin)
      8. 7.3.8 Soft Start and Recovery From Dropout
      9. 7.3.9 Safety Features
        1. 7.3.9.1 Power-Good Monitor
        2. 7.3.9.2 Redundant VOUT Monitor
        3. 7.3.9.3 Fault Output
        4. 7.3.9.4 Voltage Reference Monitor
        5. 7.3.9.5 Start-Up Diagnostics
        6. 7.3.9.6 Overcurrent and Short-Circuit Protection
        7. 7.3.9.7 Hiccup
        8. 7.3.9.8 Thermal Shutdown
        9. 7.3.9.9 Redundant Temperature Sensor
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
        1. 7.4.2.1 Peak Current Mode Operation
        2. 7.4.2.2 Auto Mode Operation
          1. 7.4.2.2.1 Diode Emulation
        3. 7.4.2.3 FPWM Mode Operation
        4. 7.4.2.4 Dropout
        5. 7.4.2.5 Recovery from Dropout
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Choosing the Switching Frequency
        3. 8.2.2.3 FB for Adjustable or Fixed Output Voltage Mode
        4. 8.2.2.4 Inductor Selection
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Input Capacitor Selection
        7. 8.2.2.7 CBOOT
        8. 8.2.2.8 External UVLO
        9. 8.2.2.9 Maximum Ambient Temperature
      3. 8.2.3 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Ground and Thermal Considerations
      2. 8.5.2 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
    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

7.1 Overview

The LM684x5-Q1 is a family of high-efficiency, high-power density, ultra-low EMI buck converters developed for functional safety-relevant applications. These converters operate over a wide input voltage range of 3V to 42V with pin selectable fixed output voltages of 3.3V, 5V, or as in adjustable output configuration.

The current-mode control architecture, with 30ns typical minimum on-time, allows high conversion ratios at high frequencies, fast transient response, and excellent load and line regulation. If the minimum on-time or minimum off-time does not support the desired conversion ratio, the switching frequency is automatically reduced. This feature allows regulation to be maintained during load dump events and cold cranking situations.

This device is designed to minimize end-product cost and size while operating in demanding automotive and high-performance industrial environments. The LM684x5-Q1 can be set to operate at fixed 400kHz, fixed 2.2MHz, or in adjustable mode from 300kHz to 2.2MHz by using the RT pin. An integrated compensation network combined with an accurate current limit scheme minimizes bill of material cost and component count.

The LM684x5-Q1 has been designed for low EMI. The device includes the following:

  • ±5% dual random spread spectrum (DRSS) significantly reducing peak emissions
  • Symmetrical pin out minimizing parasitic package inductance
  • Operation over a frequency range above and below AM radio band
  • Pin-configurable for AUTO or FPWM mode along with external clock synchronization capabilities
These features can eliminate shielding and other expensive EMI mitigation measures.

The LM684x5-Q1 has also been designed for safety applications. The following safety features are included:

  • Power-Good monitor with output UV/OV protection features, and an open-drain PG pin output
  • Redundant output voltage monitor, fast-response OV protection, and an open-drain nFAULT output, fault latching, and auto-retry provisions
  • Fully redundant internal voltage reference and monitor
  • Start-up diagnostics
  • Overcurrent and short-circuit protection with HICCUP mode
  • Thermal shutdown
  • Junction temperature monitor
These safety features significantly reduce the die and package residual FIT rates to achieve the desired ASIL / SIL levels.

To use the device in reliability-conscious environments, the LM684x5-Q1 has a package with enlarged corner terminals for improved board level reliability and wettable flanks, allowing optical inspection.