ZHCSH05A October 2017 – October 2019 LM76002 , LM76003
PRODUCTION DATA.
- 1 特性
- 2 應用
- 3 說明
- 4 修訂歷史記錄
- 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, Peak-Current-Mode Control
- 7.3.2 Light Load Operation Modes — PFM and FPWM
- 7.3.3 Adjustable Output Voltage
- 7.3.4 Enable (EN Pin) and UVLO
- 7.3.5 Internal LDO, VCC UVLO, and Bias Input
- 7.3.6 Soft Start and Voltage Tracking (SS/TRK)
- 7.3.7 Adjustable Switching Frequency (RT) and Frequency Synchronization
- 7.3.8 Minimum On-Time, Minimum Off-Time, and Frequency Foldback at Dropout Conditions
- 7.3.9 Internal Compensation and CFF
- 7.3.10 Bootstrap Voltage and VBOOT UVLO (BOOT Pin)
- 7.3.11 Power Good and Overvoltage Protection (PGOOD)
- 7.3.12 Overcurrent and Short-Circuit Protection
- 7.3.13 Thermal Shutdown
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 Custom Design With WEBENCH® Tools
- 8.2.2.2 Output Voltage Setpoint
- 8.2.2.3 Switching Frequency
- 8.2.2.4 Input Capacitors
- 8.2.2.5 Inductor Selection
- 8.2.2.6 Output Capacitor Selection
- 8.2.2.7 Feed-Forward Capacitor
- 8.2.2.8 Bootstrap Capacitors
- 8.2.2.9 VCC Capacitors
- 8.2.2.10 BIAS Capacitors
- 8.2.2.11 Soft-Start Capacitors
- 8.2.2.12 Undervoltage Lockout Setpoint
- 8.2.2.13 PGOOD
- 8.2.2.14 Synchronization
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文檔支持
- 12機械、封裝和可訂購信息
10.1.2 Compact Layout for EMI Reduction
Radiated EMI is generated by the high di/dt components in pulsing currents in switching converters. The larger area covered by the path of a pulsing current, the more electromagnetic emission is generated. The key to minimize radiated EMI is to identify the pulsing current path and minimize the area of the path. In Buck converters, the pulsing current path is from the VIN side of the input capacitors to HS switch, to the LS switch, and then return to the ground of the input capacitors, as shown in Figure 85.
Figure 85. Buck Converter High di / dt Path High frequency ceramic bypass capacitors at the input side provide primary path for the high di/dt components of the pulsing current. Placing ceramic bypass capacitor(s) as close as possible to the PVIN and PGND pins is the key to EMI reduction. The SW pin connecting to the inductor should be as short as possible, and just wide enough to carry the load current without excessive heating. Short, thick traces or copper pours (shapes) should be used for high current condution path to minimize parasitic resistance. The output capacitors should be place close to the VOUT end of the inductor and closely grounded to PGND pin and exposed PAD. Place the bypass capacitors on VCC and BIAS pins as close as possible to the pins respectively and closely grounded to PGND and the exposed PAD.