SNOS510Q November   1999  – October 2016 LP2985LV-N

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 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 Multiple Voltage Options
      2. 7.3.2 Output Voltage Accuracy
      3. 7.3.3 Ultra-Low-Dropout Voltage
      4. 7.3.4 Low Ground Current
      5. 7.3.5 Sleep Mode
      6. 7.3.6 Internal Protection Circuitry
        1. 7.3.6.1 Short Circuit Protection (Current Limit)
        2. 7.3.6.2 Thermal Protection
      7. 7.3.7 Enhanced Stability
      8. 7.3.8 Low Noise
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation with VOUT(TARGET) + 0.6 V ≥ VIN > 16 V
      2. 7.4.2 Operation With ON/OFF Control
  8. 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 External Capacitors
          1. 8.2.2.1.1 Input Capacitor
          2. 8.2.2.1.2 Output Capacitor
          3. 8.2.2.1.3 Noise Bypass Capacitor
        2. 8.2.2.2 Capacitor Characteristics
          1. 8.2.2.2.1 Tantalum
        3. 8.2.2.3 On/OFF Input Operation
        4. 8.2.2.4 Reverse Input-Output Voltage
        5. 8.2.2.5 Power Dissipation
        6. 8.2.2.6 Estimating Junction Temperature
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 DSBGA Mounting
    4. 10.4 DSBGA Light Sensitivity
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
      2. 11.1.2 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

10 Layout

10.1 Layout Guidelines

For best overall performance, place all circuit components on the same side of the circuit board and as near as practical to the respective LDO pin connections. Place ground return connections to the input and output capacitor, and to the LDO ground pin as close as possible to each other, connected by a wide, component-side, copper surface. The use of vias and long traces to create LDO circuit connections is strongly discouraged and negatively affects system performance. This grounding and layout scheme minimizes inductive parasitics, and thereby reduces load-current transients, minimizes noise, and increases circuit stability.

A ground reference plane is also recommended and is either embedded in the PCB itself or located on the bottom side of the PCB opposite the components. This reference plane serves to assure accuracy of the output voltage, shield noise, and behaves similar to a thermal plane to spread (or sink) heat from the LDO device. In most applications, this ground plane is necessary to meet thermal requirements.

10.2 Layout Example

LP2985LV-N layoutex_SNOS150.gif Figure 36. LP2985 SOT-23 Package Typical Layout
LP2985LV-N DSBGAlayout_SNOS150.gif Figure 37. LP2985 DSBGA Package Typical Layout

10.3 DSBGA Mounting

The DSBGA package requires specific mounting techniques which are detailed in AN-1112 DSBGA Wafer Level Chip Scale Package. Referring to the section Surface Mount Technology (SMT) Assembly Considerations, note that the pad style which must be used with the 5-pin package is the NSMD (non-solder mask defined) type.

For best results during assembly, alignment ordinals on the PC board may be used to facilitate placement of the DSBGA device.

10.4 DSBGA Light Sensitivity

Exposing the DSBGA device to direct sunlight cause misoperation of the device. Light sources such as Halogen lamps can also affect electrical performance if brought near to the device.

The wavelengths which have the most detrimental effect are reds and infra-reds, which means that the fluorescent lighting used inside most buildings has very little effect on performance. A DSBGA test board was brought to within 1 cm of a fluorescent desk lamp and the effect on the regulated output voltage was negligible, showing a deviation of less than 0.1% from nominal.