SLVSDH0C December   2016  – January 2018 TPS22810

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Schematic
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin 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 Switching Characteristics
    7. 7.7 Typical DC Characteristics
    8. 7.8 Typical AC Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 On and Off Control
      2. 9.3.2 Quick Output Discharge (QOD)
        1. 9.3.2.1 QOD when System Power is Removed
        2. 9.3.2.2 Internal QOD Considerations
      3. 9.3.3 EN/UVLO
      4. 9.3.4 Adjustable Rise Time (CT)
      5. 9.3.5 Thermal Shutdown
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 ON and OFF Control
    3. 10.3 Input Capacitor (Optional)
    4. 10.4 Output Capacitor (Optional)
    5. 10.5 Typical Application
      1. 10.5.1 Design Requirements
      2. 10.5.2 Detailed Design Procedure
        1. 10.5.2.1 Shutdown Sequencing During Unexpected Power Loss
        2. 10.5.2.2 VIN to VOUT Voltage Drop
        3. 10.5.2.3 Inrush Current
      3. 10.5.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Considerations
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Developmental Support
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

9.3.2 Quick Output Discharge (QOD)

The TPS22810 includes a QOD feature. The QOD pin can be configured in one of three ways:

  • QOD pin shorted to VOUT pin. Using this method, the discharge rate after the switch becomes disabled is controlled with the value of the internal resistance RPD. The value of this resistance is listed in the Electrical Characteristics table.
  • QOD pin connected to VOUT pin using an external resistor REXT. After the switch becomes disabled, the discharge rate is controlled by the value of the total resistance of the QOD. To adjust the total QOD resistance, Equation 1 can be used.
    • Equation 1. RQOD = RPD + REXT

    where

    • RQOD is the total output discharge resistance
    • RPD is the internal pulldown resistance
    • REXT is the external resistance placed between the VOUT and QOD pin.
  • QOD pin is unused and left floating. Using this method, there is no quick output discharge functionality, and the output remains floating after the switch is disabled.

Note that during thermal shutdown, the QOD functionality is not available. The device does not discharge the load as RPD does not become engaged.

The fall times of the device depend on many factors including the total resistance of the QOD, VIN, and the output capacitance. When QOD is connected to VOUT, the fall time changes over VIN as the internal RPD varies over VIN. To calculate the approximate fall time of VOUT for a given RQOD, use Equation 2 and Table 1.

Equation 2. VCAP = VIN × e-t/τ

where

  • VCAP is the voltage across the capacitor (V)
  • t is the time since power supply removal (s)
  • τ is the time constant equal to RQOD × CL

The fall times' dependency on VIN becomes minimal as the QOD value increases with additional external resistance. See Table 1 for QOD fall times.

Table 1. QOD Fall Times

VIN (V) FALL TIME (μs) 90% - 10%, CIN = 1 μF, IOUT = 0 A , VIN = 0 V, ON = 0 V(1)
TA = 25°C TA = 85°C
CL = 1 μF CL = 10 μF CL = 100 μF CL = 1 μF CL = 10 μF CL = 100 μF
18 470 4700 47000 470 4700 47000
12 450 4500 45000 450 4500 45000
9 440 4400 44000 440 4400 44000
5 500 5000 50000 480 4800 48000
3.3 600 6000 60000 570 5700 57000
(1) TYPICAL VALUES WITH QOD SHORTED TO VOUT