ZHCSL46D March 2020 – June 2021 LM62440-Q1
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Description (continued)
- 6 Device Comparison Table
- 7 Pin Configuration and Functions
- 8 Specifications
-
9 Detailed Description
- 9.1 Overview
- 9.2 Functional Block Diagram
- 9.3
Feature Description
- 9.3.1 EN Uses for Enable and VIN UVLO
- 9.3.2 MODE/SYNC Pin Operation
- 9.3.3 PGOOD Output Operation
- 9.3.4 Internal LDO, VCC UVLO, and BIAS Input
- 9.3.5 Bootstrap Voltage and VCBOOT-UVLO (CBOOT Pin)
- 9.3.6 Adjustable SW Node Slew Rate
- 9.3.7 Spread Spectrum
- 9.3.8 Soft Start and Recovery From Dropout
- 9.3.9 Output Voltage Setting
- 9.3.10 Overcurrent and Short Circuit Protection
- 9.3.11 Thermal Shutdown
- 9.3.12 Input Supply Current
- 9.4 Device Functional Modes
-
10Application and Implementation
- 10.1 Application Information
- 10.2
Typical Application
- 10.2.1 Design Requirements
- 10.2.2
Detailed Design Procedure
- 10.2.2.1 Choosing the Switching Frequency
- 10.2.2.2 Setting the Output Voltage
- 10.2.2.3 Inductor Selection
- 10.2.2.4 Output Capacitor Selection
- 10.2.2.5 Input Capacitor Selection
- 10.2.2.6 BOOT Capacitor
- 10.2.2.7 BOOT Resistor
- 10.2.2.8 VCC
- 10.2.2.9 BIAS
- 10.2.2.10 CFF and RFF Selection
- 10.2.2.11 External UVLO
- 10.2.3 Application Curves
- 11Power Supply Recommendations
- 12Layout
- 13Device and Documentation Support
- 14Mechanical, Packaging, and Orderable Information
9.4.3.3 FPWM Mode - Light Load Operation
Like auto mode operation, FPWM operation is selected using the MODE/SYNC pin, see Section 9.
In FPWM Mode, frequency is maintained while lightly loaded. To maintain frequency, a limited reverse current is allowed to flow through the inductor. Reverse current is limited by reverse current limit circuitry, see Section 8.5 for reverse current limit values.
Transitions between auto mode and FPWM mode can be commanded during operation if you are using the LM62440-Q1. These transitions are gradual, taking tens of clock cycles, allowing minimal disruption of output voltage during transitions. If the load is heavy enough to operate in CCM, since operation is identical in FPWM and Auto mode, no change in behavior is visible until the next time the circuit is lightly loaded.
For all devices, in FPWM mode, frequency reduction is still available if output voltage is high enough to command minimum on-time even while lightly loaded, allowing good behavior during faults which involve output being pulled up.