SNVS288K September   2004  – September 2018 LM2734

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
      2.      Efficiency vs Load Current VIN = 5 V, VOUT = 3.3 V
  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 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 Output Overvoltage Protection
      2. 7.3.2 Undervoltage Lockout
      3. 7.3.3 Current Limit
      4. 7.3.4 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable Pin / Shutdown Mode
      2. 7.4.2 Soft Start
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Boost Function
    2. 8.2 Typical Applications
      1. 8.2.1  LM2734X (1.6 MHz) VBOOST Derived from VIN 5V to 1.5 V/1 A
        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 Inductor Selection
          3. 8.2.1.2.3 Input Capacitor
          4. 8.2.1.2.4 Output Capacitor
          5. 8.2.1.2.5 Catch Diode
          6. 8.2.1.2.6 Boost Diode
          7. 8.2.1.2.7 Boost Capacitor
          8. 8.2.1.2.8 Output Voltage
        3. 8.2.1.3 Application Curves
      2. 8.2.2  LM2734X (1.6 MHz) VBOOST Derived from VOUT 12 V to 3.3 V /1 A
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3  LM2734X (1.6 MHz) VBOOST Derived from VSHUNT 18 V to 1.5 V /1 A
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Curves
      4. 8.2.4  LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A
        1. 8.2.4.1 Design Requirements
        2. 8.2.4.2 Detailed Design Procedure
        3. 8.2.4.3 Application Curves
      5. 8.2.5  LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V /1 A
        1. 8.2.5.1 Design Requirements
        2. 8.2.5.2 Detailed Design Procedure
        3. 8.2.5.3 Application Curves
      6. 8.2.6  LM2734Y (550 kHz) VBOOST Derived from VIN 5 V to 1.5 V / 1 A
        1. 8.2.6.1 Design Requirements
        2. 8.2.6.2 Detailed Design Procedure
        3. 8.2.6.3 Application Curves
      7. 8.2.7  LM2734Y (550 kHz) VBOOST Derived from VOUT 12 V to 3.3 V / 1 A
        1. 8.2.7.1 Design Requirements
        2. 8.2.7.2 Detailed Design Procedure
        3. 8.2.7.3 Application Curves
      8. 8.2.8  LM2734Y (550 kHz) VBOOST Derived from VSHUNT 18 V to 1.5 V / 1 A
        1. 8.2.8.1 Design Requirements
        2. 8.2.8.2 Detailed Design Procedure
        3. 8.2.8.3 Application Curves
      9. 8.2.9  LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A
        1. 8.2.9.1 Design Requirements
        2. 8.2.9.2 Detailed Design Procedure
        3. 8.2.9.3 Application Curves
      10. 8.2.10 LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V / 1 A
        1. 8.2.10.1 Design Requirements
        2. 8.2.10.2 Detailed Design Procedure
        3. 8.2.10.3 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 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 Third-Party Products Disclaimer
    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

8.2.1.2.3 Input Capacitor

An input capacitor is necessary to ensure that VIN does not drop excessively during switching transients. The primary specifications of the input capacitor are capacitance, voltage, RMS current rating, and ESL (Equivalent Series Inductance). The recommended input capacitance is 10 µF, although 4.7 µF is sufficient for input voltages below 6 V. The input voltage rating is specifically stated by the capacitor manufacturer. Make sure to check any recommended deratings and also verify if there is any significant change in capacitance at the operating input voltage and the operating temperature. The input capacitor maximum RMS input current rating (IRMS-IN) must be greater than:

Equation 21. LM2734 20102324.gif

From Equation 21 from the above equation that maximum RMS capacitor current occurs when D = 0.5. Always calculate the RMS at the point where the duty cycle, D, is closest to 0.5. The ESL of an input capacitor is usually determined by the effective cross sectional area of the current path. A large leaded capacitor will have high ESL and a 0805 ceramic chip capacitor will have very low ESL. At the operating frequencies of the LM2734 device, certain capacitors may have an ESL so large that the resulting impedance (2πfL) will be higher than that required to provide stable operation. As a result, surface-mount capacitors are strongly recommended. Sanyo POSCAP, Tantalum or Niobium, Panasonic SP or Cornell Dubilier ESR, and multilayer ceramic capacitors (MLCC) are all good choices for both input and output capacitors and have very low ESL. For MLCCs it is recommended to use X7R or X5R dielectrics. Consult the capacitor manufacturer data sheet to see how rated capacitance varies over operating conditions.