SLVS841F November   2008  – August 2016 TPS2552 , TPS2552-1 , TPS2553 , TPS2553-1

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  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. Parameter Measurement Information
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Overcurrent Conditions
      2. 9.3.2 Reverse-Voltage Protection
      3. 9.3.3 FAULT Response
      4. 9.3.4 Undervoltage Lockout (UVLO)
      5. 9.3.5 ENABLE (EN or EN)
      6. 9.3.6 Thermal Sense
    4. 9.4 Device Functional Modes
    5. 9.5 Programming
      1. 9.5.1 Programming the Current-Limit Threshold
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Constant-Current vs Latch-Off Operation and Impact on Output Voltage
    2. 10.2 Typical Applications
      1. 10.2.1 Two-Level Current-Limit Circuit
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedures
          1. 10.2.1.2.1 Designing Above a Minimum Current Limit
          2. 10.2.1.2.2 Designing Below a Maximum Current Limit
          3. 10.2.1.2.3 Accounting for Resistor Tolerance
          4. 10.2.1.2.4 Input and Output Capacitance
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Auto-Retry Functionality
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
      3. 10.2.3 Typical Application as USB Power Switch
        1. 10.2.3.1 Design Requirements
          1. 10.2.3.1.1 USB Power-Distribution Requirements
        2. 10.2.3.2 Detailed Design Procedure
          1. 10.2.3.2.1 Universal Serial Bus (USB) Power-Distribution Requirements
  11. 11Power Supply Recommendations
    1. 11.1 Self-Powered and Bus-Powered Hubs
    2. 11.2 Low-Power Bus-Powered and High-Power Bus-Powered Functions
    3. 11.3 Power Dissipation and Junction Temperature
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
    2. 13.2 Related Links
    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

Package Options

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

11 Power Supply Recommendations

11.1 Self-Powered and Bus-Powered Hubs

A SPH has a local power supply that powers embedded functions and downstream ports. This power supply must provide between 4.75 V to 5.25 V to downstream facing devices under full-load and no-load conditions. SPHs are required to have current-limit protection and must report overcurrent conditions to the USB controller. Typical SPHs are desktop PCs, monitors, printers, and stand-alone hubs.

A BPH obtains all power from an upstream port and often contains an embedded function. It must power up with less than 100 mA. The BPH usually has one embedded function, and power is always available to the controller of the hub. If the embedded function and hub require more than 100 mA on power up, keep the power to the embedded function off until enumeration is completed. This can be accomplished by removing power or by shutting off the clock to the embedded function. Power-switching the embedded function is not necessary if the aggregate power draw for the function and controller is less than 100 mA. The total current drawn by the bus-powered device is the sum of the current to the controller, the embedded function, and the downstream ports, and it is limited to 500 mA from an upstream port.

11.2 Low-Power Bus-Powered and High-Power Bus-Powered Functions

Both low-power and high-power bus-powered functions obtain all power from upstream ports. Low-power functions always draw less than 100 mA; high-power functions must draw less than 100 mA at power up and can draw up to 500 mA after enumeration. If the load of the function is more than the parallel combination of 44 Ω and 10 µF at power up, the device must implement inrush current limiting.

11.3 Power Dissipation and Junction Temperature

The low ON-resistance of the N-channel MOSFET allows small surface-mount packages to pass large currents. It is good design practice to estimate power dissipation and junction temperature. The below analysis gives an approximation for calculating junction temperature based on the power dissipation in the package. However, it is important to note that thermal analysis is strongly dependent on additional system level factors. Such factors include air flow, board layout, copper thickness and surface area, and proximity to other devices dissipating power. Good thermal design practice must include all system level factors in addition to individual component analysis.

Begin by determining the rDS(on) of the N-channel MOSFET relative to the input voltage and operating temperature. As an initial estimate, use the highest operating ambient temperature of interest and read rDS(on) from the typical characteristics graph. Using this value, the power dissipation can be calculated using Equation 7.

Equation 7. PD = rDS(on) × IOUT 2

where

  • PD = Total power dissipation (W)
  • rDS(on) = Power switch on-resistance (Ω)
  • IOUT = Maximum current-limit threshold (A)
  • This step calculates the total power dissipation of the N-channel MOSFET.

Finally, calculate the junction temperature:

Equation 8. TJ = PD × θJA + TA

where

  • TA = Ambient temperature (°C)
  • θJA = Thermal resistance (°C/W)
  • PD = Total power dissipation (W)

Compare the calculated junction temperature with the initial estimate. If they are not within a few degrees, repeat the calculation using the refined rDS(on) from the previous calculation as the new estimate. Two or three iterations are generally sufficient to achieve the desired result. The final junction temperature is highly dependent on thermal resistance θJA, and thermal resistance is highly dependent on the individual package and board layout. The Thermal Information table provides example thermal resistances for specific packages and board layouts.