SLVSFM1A March   2021  – November 2023 TPS62902

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Mode Selection and Device Configuration MODE/S-CONF
      2. 7.3.2 Adjustable VO Operation (External Voltage Divider)
      3. 7.3.3 Setable VO Operation (VSET and Internal Voltage Divider)
      4. 7.3.4 Soft Start / Tracking (SS/TR)
      5. 7.3.5 Smart Enable with Precise Threshold
      6. 7.3.6 Power Good (PG)
      7. 7.3.7 Undervoltage Lockout (UVLO)
      8. 7.3.8 Current Limit And Short Circuit Protection
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Pulse Width Modulation (PWM) Operation
      2. 7.4.2 AEE (Automatic Efficiency Enhancement)
      3. 7.4.3 Power Save Mode Operation (Auto PFM/PWM)
      4. 7.4.4 100% Duty-Cycle Operation
      5. 7.4.5 Output Discharge Function
      6. 7.4.6 Starting into a Pre-Biased Load
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application with Adjustable Output Voltage
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Programming the Output Voltage
        3. 8.2.2.3 External Component Selection
        4. 8.2.2.4 Inductor Selection
        5. 8.2.2.5 Capacitor Selection
          1. 8.2.2.5.1 Output Capacitor
          2. 8.2.2.5.2 Input Capacitor
          3. 8.2.2.5.3 Soft-Start Capacitor
        6. 8.2.2.6 Tracking Function
        7. 8.2.2.7 Output Filter and Loop Stability
      3. 8.2.3 Application Curves
      4. 8.2.4 Typical Application with Setable VO using VSET
        1. 8.2.4.1 Design Requirements
        2. 8.2.4.2 Detailed Design Procedure
        3. 8.2.4.3 Application Curves
    3. 8.3 System Examples
      1. 8.3.1 LED Power Supply
      2. 8.3.2 Powering Multiple Loads
      3. 8.3.3 Voltage Tracking
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
        1. 8.5.2.1 Thermal Considerations
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 Custom Design With WEBENCH® Tools
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
  • RPJ|9
Thermal pad, mechanical data (Package|Pins)
Orderable Information
8.2.2.5.3 Soft-Start Capacitor

A capacitor connected between SS/TR pin and GND allows a user-programmable start-up slope of the output voltage.

GUID-447DED75-A3F7-4743-8428-B465A5B4E593-low.gif Figure 8-2 Soft-Start Operation Simplified Schematic

An internal constant current source is provided to charge the external capacitance. A typical soft-start ramp time is given by:

Equation 14. T S S = C S S I S S × V R E F + 55

where

  • CSS is the capacitance required at the SS/TR pin, the unit is pF.
  • TSS is the desired soft-start ramp time, the unit is µs.
  • ISS is the SS/TR source current, the unit is µA, see the Electrical Characteristics
  • VREF is the feedback regulation voltage (VFB/0.75), the unit is V, see the Electrical Characteristics

The fastest achievable typical ramp time is 150 µs, even if the external Css capacitance is lower than 680 pF or the pin is open. Generally, lower than 1 ms soft-start time is not recommanded for low inrush current.

The soft-start time has variation, for more accurate configuration, the below maximum and minimum formula need to be taken into consideration.

Equation 15. T S S _ m a x = C S S _ m a x I S S _ m i n × V R E F _ m a x + 160
Equation 16. T S S _ m i n = C S S _ m i n I S S _ m a x × V R E F _ m i n - K

where K is the related to the value of CSS, the unit is µs, the relationship curve is shown in Figure 8-3 and Figure 8-4.

GUID-20231103-SS0I-ZLWH-DKXH-3MC2KPSMT4HW-low.svg Figure 8-3 Relationship curve of K and Css (680pF-4800pF)
GUID-20231103-SS0I-XPQN-NHKX-BTFSQXBK5JP6-low.svg Figure 8-4 Relationship curve of K and Css (4800pF-114000pF)