JAJSBA0Q January   2000  – December 2017 LP2950-N , LP2951-N

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
    1.     LP2951の概略回路図
  3. 3 概要
    1.     LP2950-Nの概略回路図
  4. 4 改訂履歴
  5. 5 Voltage Options
  6. 6 Pin Configuration and Functions
    1.     Pin Functions: LP2950-N
    2.     Pin Functions: LP2951-N
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information: LP2950-N
    5. 7.5 Thermal Information: LP2951-N
    6. 7.6 Electrical Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 Fixed Voltage Options and Programmable Voltage Version
      2. 8.3.2 High Accuracy Output Voltage
      3. 8.3.3 Low Dropout Voltage
      4. 8.3.4 Shutdown Mode
      5. 8.3.5 Error Detection Comparator Output
      6. 8.3.6 Internal Protection Circuitry
        1. 8.3.6.1 Short-Circuit Protection (Current Limit)
        2. 8.3.6.2 Thermal Protection
      7. 8.3.7 Enhanced Stability
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operation with 30 V ≥ VIN > VOUT(TARGET) + 1 V
      2. 8.4.2 Operation with Shutdown Control
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1  1-A Regulator with 1.2-V Dropout
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Output Capacitor Requirements
          2. 9.2.1.2.2 Input Capacitor Requirements
          3. 9.2.1.2.3 Error Detection Comparator Output
          4. 9.2.1.2.4 Programming the Output Voltage (LP2951-N)
          5. 9.2.1.2.5 Reducing Output Noise
        3. 9.2.1.3 Application Curves
      2. 9.2.2  300-mA Regulator with 0.75-V Dropout
      3. 9.2.3  Wide Input Voltage Range Current Limiter
      4. 9.2.4  Low Drift Current Source
      5. 9.2.5  5-V Current Limiter
      6. 9.2.6  Regulator with Early Warning and Auxiliary Output
      7. 9.2.7  Latch Off When Error Flag Occurs
      8. 9.2.8  2-A Low Dropout Regulator
      9. 9.2.9  5-V Regulator with 2.5-V Sleep Function
      10. 9.2.10 Open Circuit Detector for 4 → 20-mA Current Loop
      11. 9.2.11 Regulator with State-of-Charge Indicator
      12. 9.2.12 Low Battery Disconnect
      13. 9.2.13 System Overtemperature Protection Circuit
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 WSON Mounting
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 ドキュメントのサポート
      1. 12.1.1 関連資料
    2. 12.2 関連リンク
    3. 12.3 コミュニティ・リソース
    4. 12.4 商標
    5. 12.5 静電気放電に関する注意事項
    6. 12.6 Glossary
  13. 13メカニカル、パッケージ、および注文情報

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

9.2.1.2.3 Error Detection Comparator Output

The comparator produces a logic low output whenever the LP2951-N output falls out of regulation by more than approximately 5%. This figure is the comparator's built-in offset of about 60 mV divided by the 1.235 reference voltage. (Refer to the block diagram in the front of the datasheet.) This trip level remains “5% below normal” regardless of the programmed output voltage of the 2951. For example, the error flag trip level is typically 4.75 V for a 5-V output or 11.4 V for a 12-V output. The out of regulation condition may be due either to low input voltage, current limiting, or thermal limiting.

Figure 39 below gives a timing diagram depicting the ERROR signal and the regulated output voltage as the LP2951-N input is ramped up and down. For 5 V versions, the ERROR signal becomes valid (low) at about 1.3-V input. It goes high at about 5-V input (the input voltage at which VOUT = 4.75 V). Because the LP2951-N dropout voltage is load-dependent (see curve in typical performance characteristics), the input voltage trip point (about 5 V) varies with the load current. The output voltage trip point (approx. 4.75 V) does not vary with load.

The error comparator has an open-collector output which requires an external pull up resistor. This resistor may be returned to the output or some other supply voltage depending on system requirements. In determining a value for this resistor, note that while the output is rated to sink 400 µA, this sink current adds to battery drain in a low battery condition. Suggested values range from 100 k to 1 MΩ. The resistor is not required if this output is unused.

LP2950-N LP2951-N 854620.png
*When VIN ≤ 1.3 V, the error flag pin becomes a high impedance, and the error flag voltage rises to its pullup voltage. Using VOUT as the pullup voltage (see Figure 40), rather than an external 5-V source, keeps the error flag voltage under 1.2 V (typical) in this condition. The user may wish to divide down the error flag voltage using equal-value resistors (10 kΩ suggested), to ensure a low-level logic signal during any fault condition, while still allowing a valid high logic level during normal operation.
Figure 39. ERROR Output Timing