ZHCSJX4B June   2012  – June 2019 LMR10530

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      典型应用
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin Descriptions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Recommended Operating Ratings
    3. 6.3 Electrical Characteristics
    4. 6.4 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 Frequency Foldback
      2. 7.3.2 Load Step Response
      3. 7.3.3 Output Overvoltage Protection
      4. 7.3.4 Undervoltage Lockout
      5. 7.3.5 Current Limit
      6. 7.3.6 Soft Start/Shutdown
      7. 7.3.7 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Detailed Design Procedure
        1. 8.2.1.1 Custom Design With WEBENCH® Tools
        2. 8.2.1.2 Inductor Selection
        3. 8.2.1.3 Input Capacitor
        4. 8.2.1.4 Output Capacitor
        5. 8.2.1.5 Catch Diode
        6. 8.2.1.6 Output Voltage
        7. 8.2.1.7 Efficiency Estimation
      2. 8.2.2 Application Curve
      3. 8.2.3 Other System Examples
        1. 8.2.3.1 LMR10530X Design Example 1
        2. 8.2.3.2 LMR10530X Design Example 2
        3. 8.2.3.3 LMR10530Y Design Example 3
        4. 8.2.3.4 LMR10530Y Design Example 4
  9. 9 Layout
    1. 9.1 Layout Considerations
  10. 10器件和文档支持
    1. 10.1 器件支持
      1. 10.1.1 第三方产品免责声明
      2. 10.1.2 开发支持
        1. 10.1.2.1 使用 WEBENCH® 工具创建定制设计
    2. 10.2 接收文档更新通知
    3. 10.3 社区资源
    4. 10.4 商标
    5. 10.5 静电放电警告
    6. 10.6 Glossary
  11. 11机械、封装和可订购信息

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

8.2.1.7 Efficiency Estimation

The complete LMR10530 DC/DC converter efficiency can be calculated in the following manner:

Equation 17. LMR10530 30167320.gif

or

Equation 18. LMR10530 30167322.gif

Calculations for determining the most significant power losses are shown in the following examples. Other losses totaling less than 2% are not discussed.

The main power loss (PLOSS) in the converter includes two basic types of losses: switching loss and conduction loss. In addition, there is loss associated with the power required for the internal circuitry of IC. Conduction losses usually dominate at higher output loads, whereas switching losses dominate at lower output loads. The first step in determining the losses is to calculate the duty cycle (D):

Equation 19. LMR10530 30167310.gif

VSW is the voltage drop across the internal power switch when it is on, and is equal to:

Equation 20. VSW = IOUT × RDS(ON)

VD is the forward voltage drop across the catch diode. It can be obtained from the diode manufactures Electrical Characteristics section. If the DC voltage drop across the inductor (VDCR) is accounted for, the equation becomes:

Equation 21. LMR10530 30167321.gif

The conduction losses in the catch diode are calculated as follows:

Equation 22. PDIODE = VD × IOUT × (1-D)

Often this is the single most significant power loss in the circuit. Take care to choose a Schottky diode with a low forward-voltage drop.

Another significant external power loss is the conduction loss in the output inductor. The equation can be simplified to:

Equation 23. PIND = IOUT2 × RDCR

The LMR10530 conduction loss is mainly associated with the internal power switch:

Equation 24. LMR10530 30167372.gif

If the inductor ripple current is fairly small, the conduction losses can be simplified to:

Equation 25. PCOND = IOUT2 × RDS(ON) x D

Switching losses are also associated with the internal power switch. They occur during the switch on and off transition periods, where voltages and currents overlap resulting in power loss. The simplest means to determine this loss is to empirically measuring the rise and fall times (10% to 90%) of the switch at the switch node.

Switching Power Loss is calculated as follows:

Equation 26. PSWR = 0.5 × (VIN × IOUT × fSW × TRISE)
Equation 27. PSWF = 0.5 × (VIN × IOUT × fSW × TFALL)
Equation 28. PSW = PSWR + PSWF

The power loss required for operation of the internal circuitry is given by:

Equation 29. PQ = IQ × VIN

IQ is the quiescent operating current, and is typically around 3.2 mA for the LMR10530X, and 4.3 mA for the LMR10530Y.

An example of efficiency calculation for a typical application is shown in Table 1:

Table 1. Power Loss Tabulation

CONDITIONS POWER LOSS
VIN 5 V
VOUT 3.3 V
IOUT 3 A POUT 9.9 W
VD 0.33 V PDIODE 277 mW
RDS(ON) 56 mΩ PCOND 363 mW
fSW 1.5 MHz
TRISE 10 ns PSW 225 mW
TFALL 10 ns
INDDCR 28 mΩ PIND 252 mW
IQ 3.2 mA PQ 16 mW
η 89.7%
D is calculated to be 0.72
Equation 30. PLOSS = Σ ( PCOND + PSW + PQ + PIND + PDIODE )
Equation 31. PLOSS = 1.133W