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

9.2.1.2.4 Programming the Output Voltage (LP2951-N)

The LP2951-N may be pin-strapped for the nominal fixed output voltage using its internal voltage divider by tying the output and sense pins together, and also tying the FEEDBACK and VTAP pins together. Alternatively, it may be programmed for any output voltage between its 1.235-V reference and its 30-V maximum rating. As seen in Figure 40, an external pair of resistors is required.

The complete equation for the output voltage is

Equation 7. LP2950-N LP2951-N 854659.png

where

  • VREF is the nominal 1.235-V reference voltage and IFB is the FEEDBACK pin bias current, nominally –20 nA

The minimum recommended load current of 1 µA forces an upper limit of 1.2 MΩ on the value of R2, if the regulator must work with no load (a condition often found in CMOS in standby). IFB produces a 2% typical error in VOUT which may be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100 kΩ reduces this error to 0.17% while increasing the resistor program current to 12 µA. Because the LP2951-N typically draws 60 µA at no load with pin 2 open-circuited, this is a small price to pay.

LP2950-N LP2951-N 854607.png
LP2950-N LP2951-N 854661.png
*Drive with TTL-high to shut down. Ground or leave open if shutdown feature is not to be used.
Note: Pins 2 and 6 are left open.
Figure 40. Adjustable Regulator

Stray capacitance to the LP2951-N FEEDBACK pin can cause instability. This may especially be a problem when using high value external resistors to set the output voltage. Adding a 100-pF capacitor between the OUT pin and the FEEDBACK pin, and increasing the output capacitor to at least 3.3 µF, fixes this problem.