ZHCSF14D March 2010 – October 2018 TPS54260
PRODUCTION DATA.
- 1 特性
- 2 應(yīng)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 PWM Control
- 7.3.2 Slope Compensation Output Current
- 7.3.3 Pulse-Skip Eco-Mode
- 7.3.4 Low-Dropout Operation and Bootstrap Voltage (BOOT)
- 7.3.5 Error Amplifier
- 7.3.6 Voltage Reference
- 7.3.7 Adjusting the Output Voltage
- 7.3.8 Enable and Adjusting Undervoltage Lockout
- 7.3.9 Slow-Start / Tracking Pin (SS/TR)
- 7.3.10 Overload Recovery Circuit
- 7.3.11 Sequencing
- 7.3.12 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
- 7.3.13 Overcurrent Protection and Frequency Shift
- 7.3.14 Selecting the Switching Frequency
- 7.3.15 How to Interface to RT/CLK Pin
- 7.3.16 Powergood (PWRGD Pin)
- 7.3.17 Overvoltage Transient Protection
- 7.3.18 Thermal Shutdown
- 7.3.19 Small Signal Model for Loop Response
- 7.3.20 Simple Small Signal Model for Peak Current Mode Control
- 7.3.21 Small Signal Model for Frequency Compensation
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
3.3-V Output Application
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1 Custom Design With WEBENCH® Tools
- 8.2.1.2.2 Selecting the Switching Frequency
- 8.2.1.2.3 Output Inductor Selection (LO)
- 8.2.1.2.4 Output Capacitor
- 8.2.1.2.5 Catch Diode
- 8.2.1.2.6 Input Capacitor
- 8.2.1.2.7 Slow-Start Capacitor
- 8.2.1.2.8 Bootstrap Capacitor Selection
- 8.2.1.2.9 Undervoltage Lock Out Set Point
- 8.2.1.2.10 Output Voltage and Feedback Resistors Selection
- 8.2.1.2.11 Compensation
- 8.2.1.2.12 Discontinuous Mode and Eco-Mode Boundary
- 8.2.1.2.13 Power Dissipation Estimate
- 8.2.1.3 Application Curves
- 8.2.2 Inverting Power Supply
- 8.2.3 Split-Rail Power Supply
- 8.2.4 12-V to 3.8-V GSM Power Supply
- 8.2.5 24-V to 4.2-V GSM Power Supply
- 8.2.1
3.3-V Output Application
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文檔支持
- 12機(jī)械、封裝和可訂購信息
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
訂購信息
7.3.9 Slow-Start / Tracking Pin (SS/TR)
The TPS54260 effectively uses the lower voltage of the internal voltage reference or the SS/TR pin voltage as the power-supply's reference voltage and regulates the output accordingly. A capacitor on the SS/TR pin-to-ground implements a slow-start time. The TPS54260 has an internal pullup current source of 2 μA that charges the external slow-start capacitor. The calculations for the slow-start time (10% to 90%) are shown in Equation 6. The voltage reference (VREF) is 0.8 V and the slow-start current (ISS) is 2 μA. The slow-start capacitor should remain lower than 0.47 μF and greater than 0.47 nF.
At power-up, the TPS54260 will not start switching until the slow-start pin is discharged to less than 40 mV to ensure a proper power-up, see Figure 30.
Also, during normal operation, the TPS54260 will stop switching and the SS/TR must be discharged to 40 mV, when the VIN UVLO is exceeded, EN pin pulled below 1.25 V, or a thermal shutdown event occurs.
The VSENSE voltage will follow the SS/TR pin voltage with a 45-mV offset up to 85% of the internal voltage reference. When the SS/TR voltage is greater than 85% on the internal reference voltage the offset increases as the effective system reference transitions from the SS/TR voltage to the internal voltage reference (see Figure 23). The SS/TR voltage will ramp linearly until clamped at 1.7 V.
Figure 30. Operation of SS/TR Pin when Starting