ZHCSI13J October 2004 – November 2018 TPS75003
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3
Feature Description
- 7.3.1 Operation (Buck Controllers)
- 7.3.2 Enable (Buck Controllers)
- 7.3.3 UVLO (Buck Controllers)
- 7.3.4 Current Limit (Buck Controllers)
- 7.3.5 Short-Circuit Protection (Buck Controllers)
- 7.3.6 Soft-Start (Buck Controllers)
- 7.3.7 LDO Operation
- 7.3.8 Internal Current Limit (LDO)
- 7.3.9 Enable Pin (LDO)
- 7.3.10 Dropout Voltage (LDO)
- 7.3.11 Transient Response (LDO)
- 7.3.12 Thermal Protection (LDO)
- 7.3.13 Power Dissipation (LDO)
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Application
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 Input Capacitor CIN1, CIN2 Selection (Buck Controllers)
- 8.2.2.2 Inductor Value Selection (Buck Controllers)
- 8.2.2.3 External PMOS Transistor Selection (Buck Controllers)
- 8.2.2.4 Diode Selection (Buck Controllers)
- 8.2.2.5 Output Capacitor Selection (Buck Controllers)
- 8.2.2.6 Output Voltage Ripple Effect on VOUT (Buck Controllers)
- 8.2.2.7 Soft-Start Capacitor Selection (Buck Controllers)
- 8.2.2.8 Output Voltage Setting Selection (Buck Controllers)
- 8.2.2.9 Input Capacitor Selection (LDO)
- 8.2.2.10 Output Capacitor Selection (LDO)
- 8.2.2.11 Soft-Start Capacitor Selection (LDO)
- 8.2.2.12 Setting Output Voltage (LDO)
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
8.2.2.2 Inductor Value Selection (Buck Controllers)
The inductor is chosen based on inductance value and maximum current rating. Larger inductors reduce current ripple (and therefore, output voltage ripple) but are physically larger and more expensive. Inductors with lower DC resistance typically improve efficiency, but also have higher cost and larger physical size. The buck converters work well with inductor values between 4.7μH and 47μH in most applications. When selecting an inductor, the current rating should exceed the current limit set by RIS or RDS,ON (see the Current Limit (Buck Controllers) section). To determine the minimum inductor size, first determine if the device will operate in minimum on-time or minimum off-time mode. The device will operate in minimum on-time mode if Equation 6 is satisfied:
where
- RL = the inductor DC resistance
Minimum inductor size needed when operating in minimum on-time mode is given by Equation 7:
Minimum inductor size needed when operating in minimum off-time mode is given by Equation 8:
where
- ΔIL = (20%–30%) × IOUT-MAX