SLVSG70 april   2023 TPS62902-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Mode Selection and Device Configuration MODE/S-CONF
      2. 8.3.2  Adjustable VO Operation (External Voltage Divider)
      3. 8.3.3  Selectable VO Operation (VSET and Internal Voltage Divider)
      4. 8.3.4  Soft Start and Tracking (SS/TR)
        1. 8.3.4.1 Tracking Function
      5. 8.3.5  Smart Enable with Precise Threshold
      6. 8.3.6  Power Good (PG)
      7. 8.3.7  Output Discharge Function
      8. 8.3.8  Undervoltage Lockout (UVLO)
      9. 8.3.9  Current Limit and Short-Circuit Protection
      10. 8.3.10 High Temperature Specifications
      11. 8.3.11 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Forced Pulse Width Modulation (FPWM) Operation
      2. 8.4.2 Power Save Mode Operation (Auto PFM and PWM)
      3. 8.4.3 AEE (Automatic Efficiency Enhancement)
      4. 8.4.4 100% Duty-Cycle Operation
      5. 8.4.5 Starting into a Prebiased Load
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application with Adjustable Output Voltage
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Custom Design With WEBENCH® Tools
        2. 9.2.2.2 Programming the Output Voltage
        3. 9.2.2.3 External Component Selection
          1. 9.2.2.3.1 Output Filter and Loop Stability
          2. 9.2.2.3.2 Inductor Selection
          3. 9.2.2.3.3 Capacitor Selection
            1. 9.2.2.3.3.1 Output Capacitor
            2. 9.2.2.3.3.2 Input Capacitor
            3. 9.2.2.3.3.3 Soft-Start Capacitor
      3. 9.2.3 Application Curves
        1. 9.2.3.1 Application Curves Vout = 1.8 V
        2. 9.2.3.2 Application Curves Vout = 1.2 V
        3. 9.2.3.3 Application Curves Vout = 0.6 V
    3. 9.3 Typical Application with Selectable VOUT using VSET
      1. 9.3.1 Design Requirements
      2. 9.3.2 Detailed Design Procedure
        1. 9.3.2.1 Programming the Output Voltage
      3. 9.3.3 Application Curves
        1. 9.3.3.1 Application Curves Vout = 5 V
        2. 9.3.3.2 Application Curves Vout = 3.3 V
    4. 9.4 System Examples
      1. 9.4.1 LED Power Supply
      2. 9.4.2 Powering Multiple Loads
      3. 9.4.3 Voltage Tracking
      4. 9.4.4 Inverting Buck-Boost (IBB)
    5. 9.5 Power Supply Recommendations
    6. 9.6 Layout
      1. 9.6.1 Layout Guidelines
      2. 9.6.2 Layout Example
      3. 9.6.3 Thermal Considerations
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
      2. 10.1.2 Development Support
        1. 10.1.2.1 Custom Design With WEBENCH® Tools
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.4.1 Tracking Function

If a tracking function is desired, the SS/TR pin can be used for this purpose by connecting it to an external tracking voltage. The output voltage tracks that voltage with the typical gain and offset as specified in the Electrical Characteristics.

Note: In forced PWM (FPWM) mode the output voltage increases and decreases with any changes in the tracking voltage, but in auto PFM (power save) mode, the output voltage only decreases based on the load current.
GUID-FCA6A017-F98A-4117-8A75-519ACB8B5F4A-low.gif Figure 8-4 Tracking Operation Simplified Schematic
Equation 1. VFB = 0.75 × VSS/TR

When the SS/TR pin voltage is above 0.8 V, the internal voltage is clamped and the device goes to normal regulation. This action works for rising and falling tracking voltages with the same behavior, as long as the input voltage is inside the recommended operating conditions. For decreasing the SS/TR pin voltage in PFM mode, the device does not sink current from the output. The resulting decrease of the output voltage can therefore be slower than the SS/TR pin voltage if the load is light. When driving the SS/TR pin with an external voltage, do not exceed the voltage rating of the SS/TR pin, which is 6 V. The SS/TR pin is internally connected with a resistor to GND when EN = 0.

If the input voltage drops below undervoltage lockout, the output voltage goes to zero, independent of the tracking voltage. Figure 8-5 shows how to connect devices to get ratiometric and simultaneous sequencing by using the tracking function. See Section 9.4.3 in the systems examples.

GUID-20221004-SS0I-0ZN9-2B3B-NCWKLSJGD0TS-low.svg Figure 8-5 Schematic for Ratiometric and Simultaneous Start-Up

The resistive divider of R7 and R8 can be used to change the ramp rate of VOUT2 to be faster, slower, or the same as VOUT1.

A sequential start-up is achieved by connecting the PG pin of VOUT of device 1 to the EN pin of device 2. PG requires a pullup resistor. Ratiometric start-up sequence happens if both supplies are sharing the same soft-start capacitor. Equation 18 gives the soft-start time, though the SS/TR current has to be doubled. Details about these and other tracking and sequencing circuits are found in the Sequencing and Tracking With the TPS621-Family and TPS821-Family application report.

Note: If the voltage at the FB pin is below its typical value of 0.6 V, the output voltage accuracy can have a wider tolerance than specified. The current of 2.5 µA out of the SS/TR pin also has an influence on the tracking function, especially for high resistive external voltage dividers on the SS/TR pin.