ZHCSJU9E January 2007 – June 2019 TPS40077
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 Minimum Pulse Duration
- 7.3.2 Slew Rate Limit On VDD
- 7.3.3 Setting The Switching Frequency (Programming The Clock Oscillator)
- 7.3.4 Loop Compensation
- 7.3.5 Shutdown and Sequencing
- 7.3.6 Boost and LVBP Bypass Capacitance
- 7.3.7 Internal Regulators
- 7.3.8 Power Dissipation
- 7.3.9 Boost Diode
- 7.3.10 Synchronous Rectifier Control
- 7.4 Programming
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
Buck Regulator 8-V to 16-V Input, 1.8-V Output at 10 A
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1
Power Train Components
- 8.2.1.2.1.1 Output Inductor, LOUT
- 8.2.1.2.1.2 Output Capacitor, COUT, ELCO and MLCC
- 8.2.1.2.1.3 Input Capacitor, CIN ELCO and MLCC
- 8.2.1.2.1.4 Switching MOSFET, QSW
- 8.2.1.2.1.5 Rectifier MOSFET, QSR
- 8.2.1.2.1.6 Timing Resistor, RT
- 8.2.1.2.1.7 Feed-Forward and UVLO Resistor, RKFF
- 8.2.1.2.1.8 Soft-Start Capacitor, CSS
- 8.2.1.2.1.9 Short-Circuit Protection, RILIM and CILIM
- 8.2.1.2.1.10 Boost Voltage, CBOOST and DBOOST (Optional)
- 8.2.1.2.1.11 Closing the Feedback Loop, RZ1, RP1, RPZ2, RSET1, RSET2, CZ2, CP2, and CPZ1
- 8.2.1.2.1
Power Train Components
- 8.2.1.3 Application Curves
- 8.2.1
Buck Regulator 8-V to 16-V Input, 1.8-V Output at 10 A
- 8.3 Additional System Examples
- 9 Layout
- 10器件和文档支持
- 11机械、封装和可订购信息
8.2.1.2.1.3 Input Capacitor, CIN ELCO and MLCC
The input capacitor is selected to handle the ripple current of the buck stage. Also, a relatively large capacitance is used to keep the ripple voltage on the supply line low. This is especially important where the supply line has high impedance. It is recommended however, that the supply-line impedance be kept as low as possible.
The input-capacitor ripple current can be calculated using Equation 24.
IIN(AVG) is the average input current. This is calculated simply by multiplying the output dc current by the duty cycle. The ripple current in the input capacitor is 3.3 A. An 1812 MLCC using X5R material has a typical dissipation factor of 5%. For a 22-μF capacitor at 300 kHz, the ESR is approximately 4 mΩ. Two capacitors are used in parallel, so the power dissipation in each capacitor is less than 11 mW.
A 470-μF/16-V electrolytic is added to maintain the voltage on the input rail.