SNVS963C SEPTEMBER   2013  – June 2016 LM5121 , LM5121-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings: LM5121
    3. 6.3 ESD Ratings: LM5121-Q1
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Undervoltage Lockout (UVLO)
      2. 7.3.2  High Voltage VCC Regulator
      3. 7.3.3  Oscillator
      4. 7.3.4  Slope Compensation
      5. 7.3.5  Error Amplifier
      6. 7.3.6  PWM Comparator
      7. 7.3.7  Disconnection Switch Control
      8. 7.3.8  Soft-Start
      9. 7.3.9  HO and LO Drivers
      10. 7.3.10 Bypass Operation (VOUT = VIN)
      11. 7.3.11 Cycle-by-Cycle Current Limit
      12. 7.3.12 Circuit Breaker Function
      13. 7.3.13 Clock Synchronization
      14. 7.3.14 Maximum Duty Cycle
      15. 7.3.15 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Hiccup Mode Short Circuit and Overload Protection
      2. 7.4.2 MODE Control (Forced PWM Mode and Diode Emulation Mode)
      3. 7.4.3 MODE Control (Skip Cycle Mode and Pulse Skipping Mode)
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Feedback Compensation
      2. 8.1.2 Sub-Harmonic Oscillation
      3. 8.1.3 Output Overvoltage Protection
      4. 8.1.4 Input Transient Suppression
      5. 8.1.5 Inrush Current Limit Programming
      6. 8.1.6 Reverse Battery Protection + Disconnect Switch Control
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Timing Resistor RT
        2. 8.2.2.2  UVLO Divider RUV2, RUV1
        3. 8.2.2.3  Input Inductor LIN
        4. 8.2.2.4  Current Sense Resistor RS
        5. 8.2.2.5  Current Sense Filter RCSFP, RCSFN, CCS
        6. 8.2.2.6  Slope Compensation Resistor RSLOPE
        7. 8.2.2.7  Output Capacitor COUT
        8. 8.2.2.8  Input Capacitor CIN
        9. 8.2.2.9  VIN Filter RVIN, CVIN
        10. 8.2.2.10 Bootstrap Capacitor CBST and Boost Diode DBST
        11. 8.2.2.11 VCC Capacitor CVCC
        12. 8.2.2.12 Output Voltage Divider RFB1, RFB2
        13. 8.2.2.13 Soft-Start Capacitor CSS
        14. 8.2.2.14 Restart Capacitor CRES
        15. 8.2.2.15 Low-Side Power Switch QL
        16. 8.2.2.16 High-Side Power Switch QH and Additional Parallel Schottky Diode
        17. 8.2.2.17 Snubber Components
        18. 8.2.2.18 Disconnect Switch QD Selection
        19. 8.2.2.19 Freewheeling Diode DF Selection
        20. 8.2.2.20 Loop Compensation Components CCOMP, RCOMP, CHF
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Related Links
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

1 Features

  • AEC-Q100 Qualified with the following results:
    • Device Temperature Grade 1: -40°C to +125°C Ambient Operating Temperature Range
    • Device HBM ESD Classification Level 2
    • Device CDM ESD Classification Level C6
  • Maximum Input Voltage: 65 V
  • Min Input Voltage: 3.0 V (4.5 V for startup)
  • Output Voltage Up to 100 V
  • Bypass (VOUT = VIN) Operation
  • 1.2-V Reference with ±1.0% Accuracy
  • Free-Run/Synchronizable up to 1 MHz
  • Peak Current Mode Control
  • Robust Integrated 3-A Gate Drivers
  • Adaptive Dead-Time Control
  • Optional Diode Emulation Mode
  • Programmable Cycle-by-Cycle Current Limit
  • Programmable Line UVLO
  • Programmable Soft-Start
  • Thermal Shutdown Protection
  • Low Shutdown Quiescent Current: 9 μA
  • Programmable Slope Compensation
  • Programmable Skip Cycle Mode Reduces Standby Power
  • Supports External VCC Bias Supply Option
  • Load Disconnection in Shutdown Mode (True Shutdown)
  • Inrush Current Limiting
  • Hiccup Mode Short Circuit/Overload Protection
  • Circuit Breaker Function
  • Capable of Input Transient Suppression
  • Capable of Reverse Battery Protection
  • Thermally Enhanced 20-Pin HTSSOP

2 Applications

  • 12-V, 24-V, and 48-V Power Systems
  • Automotive Start-Stop
  • High Current Boost Power Supply
  • Battery Powered System

3 Description

The LM5121 is a synchronous boost controller intended for high-efficiency, high-power boost regulator applications. The control method is based upon peak current mode control. Current mode control provides inherent line feed-forward, cycle-by-cycle current limiting and ease of loop compensation.

The switching frequency is programmable up to 1 MHz. Higher efficiency is achieved using two robust N-channel MOSFET gate drivers with adaptive dead-time control. A user-selectable diode emulation mode enables discontinuous mode operation for improved efficiency at light load conditions.

The LM5121 provides disconnection switch control which completely disconnects the output from the input during an output short or a shutdown condition. During start-up sequence, inrush current is limited by the disconnection switch control.

An internal charge pump allows 100% duty cycle operation of the high-side synchronous switch (Bypass operation). Additional features include thermal shutdown, frequency synchronization, hiccup mode current limit and adjustable line undervoltage lockout.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LM5121 HTSSOP (20) 6.50 mm x 4.40 mm
LM5121-Q1
  1. For all available packages, see the orderable addendum at the end of the datasheet.

Simplified Application Diagram

LM5121 LM5121-Q1 x Simp Applic Diag.gif