ZHCSPF6B february 2022 – may 2023 LMQ66410 , LMQ66420 , LMQ66430
PRODUCTION DATA
- 1
- 1 特性
- 2 应用
- 3 说明
- 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
8.3.11 Input Supply Current
The device is designed to have very low input supply current when regulating light loads. This is achieved by powering much of the internal circuitry from the output. The VOUT/FB pin in the fixed-output voltage variants is the input to the LDO that powers the majority of the control circuits. By connecting the VOUT/FB input pin to the output node of the regulator, a small amount of current is drawn from the output. This current is reduced at the input by the ratio of VOUT / VIN.
Equation 2. 
where
- IQVIN is the total standby (switching) current consumed by the operating (switching) buck converter when unloaded.
- IQ is the current drawn from the VIN terminal.
- IEN is current drawn by the EN terminal. Include this current if EN is connected to VIN. Check ILKG-EN in the Electrical Characteristics for IEN.
- IBIAS is bias current drawn by the BIAS LDO.
- ηeff is the light-load efficiency of the buck converter with IQ_VIN removed from the input current of the buck converter. ηeff = 0.8 is a conservative value that can be used under normal operating conditions. This can be traced back as the ISUPPLY in the System Characteristics.