JAJSER6C February   2018  – March 2023 LMZM23600

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
  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
    5. 7.5 Electrical Characteristics
    6. 7.6 System Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Control Scheme
      2. 8.3.2 Soft-Start Function
      3. 8.3.3 Enable and External UVLO Function
      4. 8.3.4 Current Limit
      5. 8.3.5 Hiccup Mode
      6. 8.3.6 Power Good (PGOOD) Function
      7. 8.3.7 MODE/SYNC Function
        1. 8.3.7.1 Forced PWM Mode
        2. 8.3.7.2 Auto PFM Mode
        3. 8.3.7.3 Dropout Mode
        4. 8.3.7.4 SYNC Operation
      8. 8.3.8 Thermal Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown
      2. 8.4.2 FPWM Operation
      3. 8.4.3 Auto PFM Mode Operation
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 Maximum Input Voltage for VOUT < 2.5 V
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Custom Design With WEBENCH® Tools
        2. 9.2.2.2 Input Capacitor Selection
        3. 9.2.2.3 Output Capacitor Selection
        4. 9.2.2.4 Feedback Voltage Divider for Adjustable Output Voltage Versions
        5. 9.2.2.5 RPU - PGOOD Pullup Resistor
        6. 9.2.2.6 VIN Divider and Enable
      3. 9.2.3 Application Curves
        1. 9.2.3.1 VOUT = 5 V
        2. 9.2.3.2 VOUT = 3.3 V
        3. 9.2.3.3 VOUT = 12 V
        4. 9.2.3.4 VOUT = 15 V
        5. 9.2.3.5 VOUT = 2.5 V
        6. 9.2.3.6 VOUT = 1.2 V and VOUT = 1.8 V
        7. 9.2.3.7 VOUT = 5 V and 3.3 V Fixed Output Options
    3. 9.3 Best Design Practices
    4. 9.4 Power Supply Recommendations
      1. 9.4.1 Supply Voltage Range
      2. 9.4.2 Supply Current Capability
      3. 9.4.3 Supply Input Connections
        1. 9.4.3.1 Voltage Drops
        2. 9.4.3.2 Stability
    5. 9.5 Layout
      1. 9.5.1 Layout Guidelines
        1. 9.5.1.1 Thermal Design
      2. 9.5.2 Layout Examples
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 サード・パーティ製品に関する免責事項
      2. 10.1.2 Development Support
        1. 10.1.2.1 Custom Design With WEBENCH® Tools
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 ドキュメントの更新通知を受け取る方法
    4. 10.4 サポート・リソース
    5. 10.5 Trademarks
    6. 10.6 静電気放電に関する注意事項
    7. 10.7 用語集
  11. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Tape and Reel Information

9.2.2.2 Input Capacitor Selection

The input capacitor selection and placement on the board layout is very important for any buck converter design. This component provides the pulsing high di/dt current every switching cycle and reduces the input voltage ripple seen by the buck converter. Use a good-quality 10-µF, 1210 (3225) case size, X5R or X7R ceramic capacitor with sufficient voltage rating on the input of the device. Alternatively, in applications with strict size constraints and more stable input voltage it is possible to use a 10-µF, 1206 (3216) case size or a parallel combination of 2 × 4.7-µF, 0805 (2012), X5R or X7R capacitors. Ceramic capacitors have a DC bias dependence on their effective capacitance and can de-rate their value significantly when used at higher bias voltage. TI recommends ceramic capacitors with ≥ 50-V rating when using the device with a 24-V input supply. TI recommends ceramic capacitors with ≥ 25-V rating when using the device with a 12-V input supply.

Just like with any buck converter, place the input capacitor as close as possible and next to the LMZM23600. Connect the capacitor directly to the VIN (pin 3) and GND (pin 1) terminals of the device. This placement ensures that the area of the high di/dt current loop in the buck converter is kept to a minimum, resulting in the lowest possible inductance in the switching current path. The proper placement of the input capacitor in any buck converter helps to keep the output noise of the converter to a minimum. See Table 9-2 for several input capacitor choices.

Table 9-2 Input Capacitor Selection
VALUEVOLTAGE RATINGCASE SIZEDIELECTRICQUANTITYVENDORPART NUMBER
10 µF50 V1210 (3225)X7R1TDKC3225X7R1H106M250AC
10 µF50 V1210 (3225)X7R1MuRataGRJ32ER71H106KE11
10 µF50 V1206 (3216)X5R1TDKC3216X5R1H106K160AB
4.7 µF50 V0805 (2012)X5R2TDKC2012X5R1H475K125AB

For this design example a single 10-µF, 50-V 1210 X7R capacitor is used.