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
8.2.1.2.1.10 Boost Voltage, CBOOST and DBOOST (Optional)
To be able to drive an N-channel MOSFET in the switch location of a buck converter, a capacitor charge pump or boost circuit is required. The TPS40077 contains the elements for this boost circuit. The designer must only add a capacitor, CBOOST, from the switch node of the buck power stage to the BOOST pin of the IC. Selection of this capacitor is based on the total gate charge of the switching MOSFET and the allowable ripple on the boost voltage, ΔVBOOST. A ripple of 0.2 V is assumed for this design. Using these two parameters and Equation 43, the minimum value for CBOOST can be calculated.
The total gate charge of the switching MOSFET is 23 nC. A minimum CBOOST of 0.092 μF is required. A 0.1 μF capacitor was chosen. This capacitor must be able to withstand the maximum input voltage plus the maximum voltage on DBP. This is 13.2 V plus 9.0 V, which is 22.2 V. A 50-V capacitor is used.
To reduce losses in the TPS40077 and to increase the available gate voltage for the switching MOSFET, an external diode can be added between the DBP pin and the BOOST pin of the IC. A small-signal Schottky diode should be used here, such as the BAT54.