ZHCSPF6B february 2022 – may 2023 LMQ66410 , LMQ66420 , LMQ66430
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Enable, Start-Up, and Shutdown
- 8.3.2 Adjustable Switching Frequency (with RT)
- 8.3.3 Power-Good Output Operation
- 8.3.4 Internal LDO, VCC, and VOUT/FB Input
- 8.3.5 Bootstrap Voltage and VBOOT-UVLO (BOOT Terminal)
- 8.3.6 Output Voltage Selection
- 8.3.7 Spread Spectrum
- 8.3.8 Soft Start and Recovery from Dropout
- 8.3.9 Current Limit and Short Circuit
- 8.3.10 Thermal Shutdown
- 8.3.11 Input Supply Current
- 8.4 Device Functional Modes
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Application
- 9.2.1 Synchronous Buck Regulator at 400 kHz
- 9.2.2 Design Requirements
- 9.2.3 Detailed Design Procedure
- 9.2.4 Application Curves
- 9.3 Best Design Practices
- 9.4 Power Supply Recommendations
- 9.5 Layout
- 10Device and Documentation Support
- 11Mechanical, Packaging, and Orderable Information
8.3.8.1 Recovery from Dropout
Any time the output voltage falls more than a few percent, output voltage ramps up slowly. This condition, called graceful recovery from dropout in this document, differs from soft start in two important ways:
- The reference voltage is set to approximately 1% above what is needed to achieve the existing output voltage.
- If the device is set to FPWM, it continues to operate in that mode during its recovery from dropout. If output voltage were to suddenly be pulled up by an external supply, the LMQ664x0 can pull down on the output. Note that all protections that are present during normal operation are in place, preventing any catastrophic failure if output is shorted to a high voltage or ground.
Figure 8-8 Recovery from
Dropout
Figure 8-9 Typical Output Recovery
from Dropout from 8 V to 4 V
Whether output voltage falls due to high load or low input voltage, after the condition that causes output to fall below its set point is removed, the output climbs at the same speed as during start-up. Figure 8-9 shows an example of this behavior.