ZHCSLU7A September 2020 – August 2021 TPS54618C-Q1
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 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 Step One: Select the Switching Frequency
- 8.2.2.2 Step Two: Select the Output Inductor
- 8.2.2.3 Step Three: Choose the Output Capacitor
- 8.2.2.4 Step Four: Select the Input Capacitor
- 8.2.2.5 Step Five: Choose the Soft-Start Capacitor
- 8.2.2.6 Step Six: Select the Bootstrap Capacitor
- 8.2.2.7 Step Eight: Select Output Voltage and Feedback Resistors
- 8.2.2.8 Step Nine: Select Loop Compensation Components
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
7.3.7 Enable and Adjusting Undervoltage Lockout
The TPS54618C-Q1 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 7-2 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) must 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 TPS54618C-Q1 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 7-2 Adjustable Undervoltage Lockout
where
- R1 and R2 are in Ω
- Ih = 1.6 µA
- Ip = 1.9 µA
- VENRISING = 1.25 V
- VENFALLING = 1.18 V