ZHCSAL1F November 2010 – May 2019 TPS54618
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 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 PWM Control
- 7.3.2 Slope Compensation and Output Current
- 7.3.3 Bootstrap Voltage (Boot) and Low Dropout Operation
- 7.3.4 Error Amplifier
- 7.3.5 Voltage Reference
- 7.3.6 Adjusting the Output Voltage
- 7.3.7 Enable and Adjusting Undervoltage Lockout
- 7.3.8 Soft-Start Pin
- 7.3.9 Sequencing
- 7.3.10 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
- 7.3.11 Overcurrent Protection
- 7.3.12 Frequency Shift
- 7.3.13 Reverse Overcurrent Protection
- 7.3.14 Synchronize Using the RT/CLK Pin
- 7.3.15 Power Good (PWRGD Pin)
- 7.3.16 Overvoltage Transient Protection
- 7.3.17 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 Step One: Select the Switching Frequency
- 8.2.2.3 Step Two: Select the Output Inductor
- 8.2.2.4 Step Three: Choose the Output Capacitor
- 8.2.2.5 Step Four: Select the Input Capacitor
- 8.2.2.6 Step Five: Choose the Soft-Start Capacitor
- 8.2.2.7 Step Six: Select the Bootstrap Capacitor
- 8.2.2.8 Step Eight: Select Output Voltage and Feedback Resistors
- 8.2.2.9 Step Nine: Select Loop Compensation Components
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
7.3.7 Enable and Adjusting Undervoltage Lockout
The TPS54618 is disabled when the VIN pin voltage falls below 2.28 V. If an application requires a higher undervoltage lockout (UVLO), use the EN pin as shown in Figure 26 to adjust the input voltage UVLO by using two external resistors. TI recommends using the EN resistors to set the UVLO falling threshold (VSTOP) above 2.6 V. The rising threshold (VSTART) should be set to provide enough hysteresis to allow for any input supply variations. The EN pin has an internal pullup current source that provides the default condition of the TPS54618 operating when the EN pin floats. Once the EN pin voltage exceeds 1.25 V, an additional 1.6 μA of hysteresis is added. When the EN pin is pulled below 1.18 V, the 1.6 μA is removed. This additional current facilitates input voltage hysteresis.
Figure 26. Adjustable Undervoltage Lockout 
vertical spacer
where
- R1 and R2 are in Ω
- Ih = 1.6 µA
- Ip = 1.9 µA
- VENRISING = 1.25 V
- VENFALLING = 1.18 V