SLVSCZ8B July   2016  – December 2019 TPS22918-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      On-Resistance vs Input Voltage Typical Values
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Switching Characteristics
    7. 6.7 Typical DC Characteristics
    8. 6.8 Typical AC Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 On and Off Control
      2. 8.3.2 Quick Output Discharge (QOD)
        1. 8.3.2.1 QOD when System Power is Removed
        2. 8.3.2.2 Internal QOD Considerations
      3. 8.3.3 Adjustable Rise Time (CT)
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Input Capacitor (CIN)
        2. 9.2.2.2 Output Capacitor (CL) (Optional)
        3. 9.2.2.3 Shutdown Sequencing During Unexpected System Power Loss
        4. 9.2.2.4 VIN to VOUT Voltage Drop
        5. 9.2.2.5 Inrush Current
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Developmental Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.2 Quick Output Discharge (QOD)

The TPS22918-Q1 includes a QOD feature. The QOD pin can be configured in one of three valid 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.

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 shorted 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 , VON = 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
5.5 42 190 1880 40 210 2150
5 43 200 1905 45 220 2200
3.3 47 230 2150 50 260 2515
2.5 58 300 2790 60 345 3290
1.8 75 430 4165 80 490 4950
1.2 135 955 9910 135 1035 10980
1 230 1830 19625 210 1800 19270
(1) Typical values with QOD shorted to VOUT