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
8.2.1.2.1.9 Short-Circuit Protection, RILIM and CILIM
Short-circuit protection is programmed using the RILIM resistor. Selection of this resistor depends on the RDS(on) of the switching MOSFET selected and the required short-circuit current trip point, ISCP. The minimum ISCP is limited by the inductor peak current, the output voltage, the output capacitor, and the soft-start time. Their relationship is given by Equation 38. A short-circuit current trip point greater than that calculated by Equation 38 should be used.
The minimum short-circuit current trip point for this design is 12.25 A. This value is used in Equation 39 to calculate the minimum RILIM value.
RILIM is calculated to be 1.17 kΩ, and a 1.2-kΩ resistor is used to verify that the short-circuit current requirements are met. The minimum and maximum short-circuit current can be calculated using Equation 40 and Equation 41.
where: VILIM(MAX) and VILIM(MIN) are maximum and minimum voltages across the high side FET when it is turned on, taking into account temperature variations.
The minimum ISCP is 12.25 A, and the maximum is 34 A.
It is also recommended to add a small capacitor, CILIM, across RILIM. The value of this capacitor should be about half the value calculated in Equation 42.
This equation yields a maximum CILIM as 55 pF. A smaller value of 27 pF is chosen is chosen.