SBVS233B January   2016  – June 2021 TPS7A84

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configurations and Functions
  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
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Low-Noise, High-PSRR Output
      2. 7.3.2  Integrated Resistance Network (ANY-OUT)
      3. 7.3.3  Bias Rail
      4. 7.3.4  Power-Good Function
      5. 7.3.5  Programmable Soft-Start
      6. 7.3.6  Internal Current Limit (ILIM)
      7. 7.3.7  Enable
      8. 7.3.8  Active Discharge Circuit
      9. 7.3.9  Undervoltage Lockout (UVLO)
      10. 7.3.10 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation with 1.1 V ≤ VIN < 1.4 V
      2. 7.4.2 Operation with 1.4 V ≤ VIN ≤ 6.5 V
      3. 7.4.3 Shutdown
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Recommended Capacitor Types
      2. 8.1.2  Input and Output Capacitor Requirements (CIN and COUT)
      3. 8.1.3  Noise-Reduction and Soft-Start Capacitor (CNR/SS)
      4. 8.1.4  Feed-Forward Capacitor (CFF)
      5. 8.1.5  Soft-Start and In-Rush Current
      6. 8.1.6  Optimizing Noise and PSRR
      7. 8.1.7  Charge Pump Noise
      8. 8.1.8  ANY-OUT Programmable Output Voltage
      9. 8.1.9  ANY-OUT Operation
      10. 8.1.10 Increasing ANY-OUT Resolution for LILO Conditions
      11. 8.1.11 Current Sharing
      12. 8.1.12 Adjustable Operation
      13. 8.1.13 Sequencing Requirements
        1. 8.1.13.1 Sequencing with a Power-Good DC-DC Converter Pin
        2. 8.1.13.2 Sequencing with a Microcontroller (MCU)
      14. 8.1.14 Power-Good Operation
      15. 8.1.15 Undervoltage Lockout (UVLO) Operation
      16. 8.1.16 Dropout Voltage (VDO)
      17. 8.1.17 Behavior when Transitioning from Dropout into Regulation
      18. 8.1.18 Load Transient Response
      19. 8.1.19 Negatively-Biased Output
      20. 8.1.20 Reverse Current Protection
      21. 8.1.21 Power Dissipation (PD)
      22. 8.1.22 Estimating Junction Temperature
      23. 8.1.23 Recommended Area for Continuous Operation (RACO)
    2. 8.2 Typical Applications
      1. 8.2.1 Low-Input, Low-Output (LILO) Voltage Conditions
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Typical Application for a 5.0-V Rail
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Board Layout
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Evaluation Modules
        2. 11.1.1.2 Spice Models
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Undervoltage Lockout (UVLO) Operation

The UVLO circuit ensures that the device stays disabled before its input or bias supplies reach the minimum operational voltage range, and ensures that the device shuts down when the input supply or bias supply collapse.

The UVLO circuit has a minimum response time of several microseconds to fully assert. During this time, a downward line transient below approximately 0.8 V causes the UVLO to assert for a short time; however, the UVLO circuit does not have enough stored energy to fully discharge the internal circuits inside of the device. When the UVLO circuit does not fully discharge, the internal circuits of the output are not fully disabled.

The effect of the downward line transient can be mitigated by either using a larger input capacitor to limit the fall time of the input supply when operating near the minimum VIN, or by using a bias rail.

Figure 8-8 shows the UVLO circuit response to various input voltage events. The diagram can be separated into the following parts:

  • Region A: The device does not turn on until the input reaches the UVLO rising threshold.
  • Region B: Normal operation with a regulated output
  • Region C: Brownout event above the UVLO falling threshold (UVLO rising threshold – UVLO hysteresis). The output may fall out of regulation but the device is still enabled.
  • Region D: Normal operation with a regulated output
  • Region E: Brownout event below the UVLO falling threshold. The device is disabled in most cases and the output falls because of the load and active discharge circuit. The device is reenabled when the UVLO rising threshold is reached by the input voltage and a normal start-up then follows.
  • Region F: Normal operation followed by the input falling to the UVLO falling threshold.
  • Region G: The device is disabled when the input voltage falls below the UVLO falling threshold to 0 V. The output falls because of the load and active discharge circuit.

GUID-BE94E3E4-CAB6-4039-A08C-CBDFE33A7A3D-low.gifFigure 8-8 Typical UVLO Operation