SLVSBD0B November   2012  – June 2020 TPS2553-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application as USB Power Switch
  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 Typical 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 Overcurrent Conditions
      2. 8.3.2 Reverse-Voltage Protection
      3. 8.3.3 FAULT Response
      4. 8.3.4 Undervoltage Lockout (UVLO)
      5. 8.3.5 Enable (EN)
      6. 8.3.6 Thermal Sense
    4. 8.4 Device Functional Modes
    5. 8.5 Programming
      1. 8.5.1 Programming the Current-Limit Threshold
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Constant-Current and Impact on Output Voltage
      2. 9.1.2 Accounting for Resistor Tolerance
      3. 9.1.3 Input and Output Capacitance
    2. 9.2 Typical Applications
      1. 9.2.1 Application 1: Designing Above a Minimum Current-Limit
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Application 2: Designing Below a Maximum Current-Limit
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
      3. 9.2.3 Application 3: Auto-Retry Functionality
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
      4. 9.2.4 Application 4: Two-Level Current-Limit Circuit
        1. 9.2.4.1 Design Requirements
        2. 9.2.4.2 Detailed Design Procedure
      5. 9.2.5 Application 5: Typical Application as USB Power Switch
        1. 9.2.5.1 Design Requirements
        2. 9.2.5.2 Detailed Design Procedure
          1. 9.2.5.2.1 Universal Serial Bus (USB) Power-Distribution Requirements
  10. 10Power Supply Recommendations
    1. 10.1 USB Self-Powered (SPH) and Bus-Powered (BPH) Hubs
    2. 10.2 USB Low-Power Bus-Powered and High-Power Bus-Powered Functions
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Power Dissipation and Junction Temperature
  12. 12Device and Documentation Support
    1. 12.1 Device Support
    2. 12.2 Support Resource
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

8.5.1 Programming the Current-Limit Threshold

The overcurrent threshold is user programmable via an external resistor. The TPS2553-Q1 device uses an internal regulation loop to provide a regulated voltage on the ILIM pin. The current-limit threshold is proportional to the current sourced out of ILIM. The recommended resistor range for RILIM is 15 kΩ ≤ RILIM ≤ 232 kΩ to ensure stability of the internal regulation loop. The resistor tolerance should be 1% or better. Many applications require that the minimum current-limit is above a certain current level or that the maximum current-limit is below a certain current level, so it is important to consider the tolerance of the overcurrent threshold when selecting a value for RILIM. The following equations and Figure 22 can be used to calculate the resulting overcurrent threshold for a given external resistor value (RILIM). Figure 22 includes current-limit tolerance due to variations caused by temperature and process. However, the equations do not account for tolerance due to external resistor variation, so it is important to account for this tolerance when selecting RILIM. The traces routing the RILIM resistor to the TPS2553-Q1 device should be as short as possible to reduce parasitic effects on the current-limit accuracy.

RILIM can be selected to provide a current-limit threshold that occurs 1) above a minimum load current or 2) below a maximum load current.

To design above a minimum current-limit threshold, find the intersection of RILIM and the maximum desired load current on the IOS(min) curve and choose a value of RILIM below this value. Programming the current-limit above a minimum threshold is important to ensure start up into full load or heavy capacitive loads. The resulting maximum current-limit threshold is the intersection of the selected value of RILIM and the IOS(max) curve.

To design below a maximum current-limit threshold, find the intersection of RILIM and the maximum desired load current on the IOS(max) curve and choose a value of RILIM above this value. Programming the current-limit below a maximum threshold is important to avoid current-limiting upstream power supplies causing the input voltage bus to droop. The resulting minimum current-limit threshold is the intersection of the selected value of RILIM and the IOS(min) curve.

Current-Limit Threshold Equations (IOS):

Equation 1. TPS2553-Q1 eq_curr_lim_lvs841.gif

where

    While the maximum recommended value of RILIM is 232 kΩ, there is one additional configuration that allows for a lower current-limit threshold. The ILIM pin may be connected directly to IN to provide a 75 mA (typical) current-limit threshold. Additional low-ESR ceramic capacitance may be necessary from IN to GND in this configuration to prevent unwanted noise from coupling into the sensitive ILIM circuitry.

    TPS2553-Q1 cur_lim_thres_lvs841.gifFigure 22. Current-Limit Threshold vs RILIM