ZHCSF41B December   2015  – March 2021 LMR16030

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  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 Switching Characteristics
    7. 6.7 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  Fixed Frequency Peak Current Mode Control
      2. 7.3.2  Slope Compensation
      3. 7.3.3  Sleep Mode
      4. 7.3.4  Low Dropout Operation and Bootstrap Voltage (BOOT)
      5. 7.3.5  Adjustable Output Voltage
      6. 7.3.6  Enable and Adjustable Undervoltage Lockout
      7. 7.3.7  External Soft Start
      8. 7.3.8  Switching Frequency and Synchronization (RT/SYNC)
      9. 7.3.9  Power Good (PGOOD)
      10. 7.3.10 Overcurrent and Short Circuit Protection
      11. 7.3.11 Overvoltage Protection
      12. 7.3.12 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 CCM Mode
      4. 7.4.4 Light Load Operation
  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 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Output Voltage Set-Point
        3. 8.2.2.3 Switching Frequency
        4. 8.2.2.4 Output Inductor Selection
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Schottky Diode Selection
        7. 8.2.2.7 Input Capacitor Selection
        8. 8.2.2.8 Bootstrap Capacitor Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 第三方产品免责声明
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 接收文档更新通知
    3. 11.3 支持资源
    4. 11.4 Trademarks
    5. 11.5 静电放电警告
    6. 11.6 术语表
  12. 12Mechanical, Packaging, and Orderable Information

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.3.8 Switching Frequency and Synchronization (RT/SYNC)

The switching frequency of the LMR16030 can be programmed by the resistor RT from the RT/SYNC pin and GND pin. The RT/SYNC pin cannot be left floating or shorted to ground. To determine the timing resistance for a given switching frequency, use Equation 5 or the curve in Figure 7-4. Table 7-1 gives typical RT values for a given fSW.

Equation 5. GUID-2D3FABDB-A4F8-4253-8156-56528749697F-low.gif
GUID-4D8875E8-6AD4-4C15-84FD-FC8F4B936038-low.gifFigure 7-4 RT Versus Frequency Curve
Table 7-1 Typical Frequency Setting RT Resistance
fSW (kHz)RT (kΩ)
200133
35073.2
50049.9
75032.4
100023.2
150015.0
191211.5
22009.76

The LMR16030 switching action can also be synchronized to an external clock from 250 kHz to 2.3 MHz. Connect a square wave to the RT/SYNC pin through either circuit network shown in Figure 7-5. Internal oscillator is synchronized by the falling edge of external clock. The recommendations for the external clock include: high level no lower than 1.7 V, low level no higher than 0.5 V, and have a pulse width greater than 30 ns. When using a low impedance signal source, the frequency setting resistor RT is connected in parallel with an AC coupling capacitor CCOUP to a termination resistor RTERM (for example, 50 Ω). The two resistors in series provide the default frequency setting resistance when the signal source is turned off. A 10 pF ceramic capacitor can be used for CCOUP. Figure 7-6, Figure 7-7, and Figure 7-8 show the device synchronized to an external system clock.

GUID-B2DEEC21-7910-4D8D-95A6-28EA497C8393-low.gifFigure 7-5 Synchronizing to an External Clock
GUID-BF3947DC-440D-4B9D-B23E-ED4A06A527BF-low.pngFigure 7-6 Synchronizing in CCM
GUID-E7413A85-3366-4802-B3F6-0C3F5F07FF44-low.pngFigure 7-8 Synchronizing in Sleep Mode
GUID-643A9EE3-F624-44F6-A13C-38DC87F00DDE-low.pngFigure 7-7 Synchronizing in DCM

Equation 6 calculates the maximum switching frequency limitation set by the minimum controllable on time and the input-to-output step-down ratio. Setting the switching frequency above this value causes the regulator to skip switching pulses to achieve the low duty cycle required at maximum input voltage.

Equation 6. GUID-3CFFA018-4299-4A33-805B-7BC8C8F3EC2E-low.gif

where

  • IOUT = Output current
  • RIND = Inductor series resistance
  • VIN_MAX = Maximum input voltage
  • VOUT = Output voltage
  • VD = Diode voltage drop
  • RDS_ON = High-side MOSFET switch on resistance
  • tON = Minimum on time