SNVSA99C July   2015  – November 2017 LM43600-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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 Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Fixed Frequency Peak Current Mode Controlled Step-Down Regulator
      2. 7.3.2  Light Load Operation
      3. 7.3.3  Adjustable Output Voltage
      4. 7.3.4  Enable (ENABLE)
      5. 7.3.5  VCC, UVLO and BIAS
      6. 7.3.6  Soft-Start and Voltage Tracking (SS/TRK)
      7. 7.3.7  Switching Frequency (RT) and Synchronization (SYNC)
      8. 7.3.8  Minimum ON-Time, Minimum OFF-Time and Frequency Foldback at Dropout Conditions
      9. 7.3.9  Internal Compensation and CFF
      10. 7.3.10 Bootstrap Voltage (BOOT)
      11. 7.3.11 Power Good (PGOOD)
      12. 7.3.12 Overcurrent and Short-Circuit Protection
      13. 7.3.13 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Stand-by Mode
      3. 7.4.3 Active Mode
      4. 7.4.4 CCM Mode
      5. 7.4.5 Light Load Operation
      6. 7.4.6 Self-Bias Mode
  8. Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1.  Custom Design With WEBENCH® Tools
        2.  Output Voltage Setpoint
        3.  Switching Frequency
        4.  Input Capacitors
        5.  Inductor Selection
        6.  Output Capacitor Selection
        7.  Feedvorward Capacitor
        8.  Bootstrap Capacitors
        9.  VCC Capacitor
        10. BIAS Capacitors
        11. Soft-Start Capacitors
        12. Undervoltage Lockout Setpoint
        13. PGOOD
      3. 8.2.3 Application Performance Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Compact Layout for EMI Reduction
      2. 10.1.2 Ground Plane and Thermal Considerations
      3. 10.1.3 Feedback Resistors
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Development Support
      1. 11.1.1 Custom Design With WEBENCH® Tools
    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

Pin Configuration and Functions

PWP Package
Top View
LM43600-Q1 po_01_snvsa13.gif

Pin Functions

SW 1, 2 P Switching output of the regulator. Internally connected to both power MOSFETs. Connect to power inductor.
CBOOT 3 P Bootstrap capacitor connection for high-side driver. Connect a high-quality 470-nF capacitor from CBOOT to SW.
VCC 4 P Internal bias supply output for bypassing. Connect bypass capacitor from this pin to AGND. Do not connect external load to this pin. Never short this pin to ground during operation.
BIAS 5 P Optional internal LDO supply input. To improve efficiency, it is recommended to tie to VOUT when 3.3 V ≤ VOUT ≤ 28 V, or tie to an external 3.3 V or 5 V rail if available. When used, place a bypass capacitor (1 to 10 µF) from this pin to ground. Tie to ground when not in use. Do not float
SYNC 6 A Clock input to synchronize switching action to an external clock. Use proper high speed termination to prevent ringing. Connect to ground if not used. Do not float.
RT 7 A Connect a resistor RT from this pin to AGND to program switching frequency. Leave floating for 500 kHz default switching frequency.
PGOOD 8 A Open drain output for power-good flag. Use a 10-kΩ to 100-kΩ pullup resistor to logic rail or other DC voltage no higher than 12 V.
FB 9 A Feedback sense input pin. Connect to the midpoint of feedback divider to set VOUT. Do not short this pin to ground during operation.
AGND 10 G Analog ground pin. Ground reference for internal references and logic. Connect to system ground.
SS/TRK 11 A Soft-start control pin. Leave floating for internal soft-start slew rate. Connect to a capacitor to extend soft start time. Connect to external voltage ramp for tracking.
EN 12 A Enable input to the LM43600-Q1: High = ON and low = OFF. Connect to VIN, or to VIN through resistor divider,or to an external voltage or logic source. Do not float.
VIN 13, 14 P Supply input pins to internal LDO and high side power FET. Connect to power supply and bypass capacitors CIN. Path from VIN pin to high frequency bypass CIN and PGND must be as short as possible.
PGND 15, 16 G Power ground pins, connected internally to the low side power FET. Connect to system ground, PAD, AGND, ground pins of CIN and COUT. Path to CIN must be as short as possible.
PAD G Low impedance connection to AGND. Connect to PGND on PCB . Major heat dissipation path of the die. Must be used for heat sinking to ground plane on PCB.
P = Power, G = Ground, A = Analog