SNVS180N April   2002  – April 2016 LM2750

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
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching 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 Pre-Regulation
      2. 7.3.2 Input, Output, and Ground Connections
      3. 7.3.3 Shutdown
      4. 7.3.4 Soft Start
      5. 7.3.5 Output Current Capability
      6. 7.3.6 Thermal Shutdown
      7. 7.3.7 Output Current Limiting
      8. 7.3.8 Programming the Output Voltage of the LM2750-ADJ
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Brightness/Dimming Control
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Output Voltage Ripple
    2. 8.2 Typical Applications
      1. 8.2.1 LM2750-ADJ Typical Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Capacitors
          2. 8.2.1.2.2 Input Capacitor
          3. 8.2.1.2.3 Flying Capacitor
          4. 8.2.1.2.4 Output Capacitor
          5. 8.2.1.2.5 Power Efficiency And Power Dissipation
        3. 8.2.1.3 Application Curve
      2. 8.2.2 LM2750 LED Drive Applications
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Requirements
          1. 8.2.2.2.1 LED Driver Power Efficiency
        3. 8.2.2.3 Application Curve
  9. 9 Power Supply Recommendations
    1. 9.1 LED Driver Power Consumption
  10. 10Layout
    1. 10.1 Layout Recommendations
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
      2. 11.2.2 Related Links
    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

9 Power Supply Recommendations

The LM2750 is designed to operate from an input voltage supply range from 2.7 V to 5.6 V. This input supply must be well regulated and capable to supply the required input current. If the input supply is located far from the device, additional bulk capacitance may be required in addition to the ceramic bypass capacitors.

9.1 LED Driver Power Consumption

For battery-powered LED-drive applications, TI strongly recommends that power consumption, rather than power efficiency, be used as the metric of choice when evaluating power conversion performance. Power consumed (PIN) is simply the product of input voltage (VIN) and input current (IIN):

Equation 14. PIN = VIN × IIN

The LM2750 input current is equal to twice the output current (IOUT), plus the supply current of the part (nominally 5 mA):

Equation 15. IIN = (2 × IOUT) + 5 mA

Output voltage and LED voltage do not impact the amount of current consumed by the LM2750 circuit. Thus, neither factor affects the current draw on a battery. Because output voltage does not impact input current, there is no power savings with either the LM2750-5.0 or the LM2750-ADJ; both options consume the same amount of power.

In LED Driver Power Efficiency, LED Driver Efficiency was defined in Equation 13.

Equation 13 can be simplified by recognizing

  • 2 × IOUT > 5 mA (high output-current applications);
  • N × ILED = IOUT

Thus, simplification yields: ELED = VLED / VIN.

This is in direct contrast to the previous assertion that showed that power consumption was completely independent of LED voltage. As is the case here with the LM2750, efficiency is often not a good measure of power conversion effectiveness of LED driver topologies. This is why it is strongly recommended that power consumption be studied or measured when comparing the power conversion effectiveness of LED drivers.

Additionally, efficiency of an LED drive solution must not be confused with an efficiency calculation for a standard power converter (EP).

Equation 16. LM2750 LM2750-ADJ standardpower_eq.gif

Equation 16 neglects power losses in the external resistors that set LED currents and is a very poor metric of LED-drive power conversion performance.