SBVS281A March   2016  – July 2016 TPS7A87

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 Voltage Regulation Features
        1. 7.3.1.1 DC Regulation
        2. 7.3.1.2 AC and Transient Response
      2. 7.3.2 System Start-Up Features
        1. 7.3.2.1 Programmable Soft-Start (NR/SSx)
        2. 7.3.2.2 Sequencing
          1. 7.3.2.2.1 Enable (ENx)
          2. 7.3.2.2.2 Undervoltage Lockout (UVLOx) Control
          3. 7.3.2.2.3 Active Discharge
        3. 7.3.2.3 Power-Good Output (PGx)
      3. 7.3.3 Internal Protection Features
        1. 7.3.3.1 Foldback Current Limit (ICLx)
        2. 7.3.3.2 Thermal Protection (Tsdx)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Regulation
      2. 7.4.2 Disabled
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 External Component Selection
        1. 8.1.1.1 Setting the Output Voltage (Adjustable Operation)
        2. 8.1.1.2 Capacitor Recommendations
        3. 8.1.1.3 Input and Output Capacitor (CINx and COUTx)
        4. 8.1.1.4 Feed-Forward Capacitor (CFFx)
        5. 8.1.1.5 Noise-Reduction and Soft-Start Capacitor (CNR/SSx)
      2. 8.1.2 Start-Up
        1. 8.1.2.1 Circuit Soft-Start Control (NR/SSx)
          1. 8.1.2.1.1 In-Rush Current
        2. 8.1.2.2 Undervoltage Lockout (UVLOx) Control
        3. 8.1.2.3 Power-Good (PGx) Function
      3. 8.1.3 AC and Transient Performance
        1. 8.1.3.1 Power-Supply Rejection Ratio (PSRR)
        2. 8.1.3.2 Channel-to-Channel Output Isolation and Crosstalk
        3. 8.1.3.3 Output Voltage Noise
        4. 8.1.3.4 Optimizing Noise and PSRR
          1. 8.1.3.4.1 Charge Pump Noise
        5. 8.1.3.5 Load Transient Response
      4. 8.1.4 DC Performance
        1. 8.1.4.1 Output Voltage Accuracy (VOUTx)
        2. 8.1.4.2 Dropout Voltage (VDO)
          1. 8.1.4.2.1 Behavior when Transitioning from Dropout into Regulation
      5. 8.1.5 Reverse Current Protection
      6. 8.1.6 Power Dissipation (PD)
        1. 8.1.6.1 Estimating Junction Temperature
        2. 8.1.6.2 Recommended Area for Continuous Operation (RACO)
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Board Layout
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Evaluation Modules
        2. 11.1.1.2 SPICE Models
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

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発注情報

10 Layout

10.1 Layout Guidelines

General guidelines for linear regulator designs are to 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 to each other as possible, 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.

10.1.1 Board Layout

To maximize the performance of the device, following the layout example illustrated in Figure 65 is recommended. This layout isolates the analog ground (AGND) from the noisy power ground. Components that must be connected to the quiet analog ground are the noise-reduction capacitors (CNR/SSx) and the lower feedback resistors (R2x). These components must have a separate connection back to the thermal pad of the device. To minimize crosstalk between the two outputs, the output capacitor grounds are positioned on opposite sides of the layout and only connect back to the device at opposite sides of the thermal pad. Connecting the GND pins directly to the thermal pad and not to any external plane is recommended.

To maximize the output voltage accuracy, the connection from each output voltage back to the top output divider resistors (R1x) must be made as close as possible to the load. This method of connecting the feedback trace eliminates the voltage drop from the device output to the load.

To improve thermal performance, a 3 × 3 thermal via array must connect the thermal pad to internal ground planes. A larger area for the internal ground planes improves the thermal performance and lowers the operating temperature of the device.

10.2 Layout Example

TPS7A87 layout_sbvs281.gif Figure 65. TPS7A87 Example Layout