ZHCSIQ5A September 2018 – August 2021 LM34936
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 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 Fixed Frequency Valley/Peak Current Mode Control with Slope Compensation
- 7.3.2 VCC Regulator and Optional BIAS Input
- 7.3.3 Enable/UVLO
- 7.3.4 Soft-Start
- 7.3.5 Overcurrent Protection
- 7.3.6 Average Input/Output Current Limiting
- 7.3.7 Operation Above 28-V Input
- 7.3.8 CCM Operation
- 7.3.9 Frequency and Synchronization (RT/SYNC)
- 7.3.10 Frequency Dithering
- 7.3.11 Output Overvoltage Protection (OVP)
- 7.3.12 Power Good (PGOOD)
- 7.3.13 Gm Error Amplifier
- 7.3.14 Integrated Gate Drivers
- 7.3.15 Thermal Shutdown
- 7.4 Device Functional Modes
-
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 Custom Design with WEBENCH Tools
- 8.2.2.2 Frequency
- 8.2.2.3 VOUT
- 8.2.2.4 Inductor Selection
- 8.2.2.5 Output Capacitor
- 8.2.2.6 Input Capacitor
- 8.2.2.7 Sense Resistor (RSENSE)
- 8.2.2.8 Slope Compensation
- 8.2.2.9 UVLO
- 8.2.2.10 Soft-Start Capacitor
- 8.2.2.11 Dither Capacitor
- 8.2.2.12 MOSFETs QH1 and QL1
- 8.2.2.13 MOSFETs QH2 and QL2
- 8.2.2.14 Frequency Compensation
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
8.2.2.5 Output Capacitor
In the boost mode, the output capacitor conducts high ripple current. The output capacitor RMS ripple current is given by Equation 19 where the minimum VIN corresponds to the maximum capacitor current.
In this example the maximum output ripple RMS current is ICOUT(RMS) = 6 A. A 5-mΩ output capacitor ESR causes an output ripple voltage of 60 mV as given by:
A 400 µF output capacitor causes a capacitive ripple voltage of 25 mV as given by:
Typically a combination of ceramic and bulk capacitors is needed to provide low ESR and high ripple current capacity. The complete schematic in Figure 8-1 at the end of this section shows a good starting point for COUT for typical applications.