SLVS503F November   2003  – February 2020 TPS2490 , TPS2491

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
  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 Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  VCC
      2. 7.3.2  SENSE
      3. 7.3.3  GATE
      4. 7.3.4  OUT
      5. 7.3.5  EN
      6. 7.3.6  VREF
      7. 7.3.7  PROG
      8. 7.3.8  TIMER
      9. 7.3.9  PG
      10. 7.3.10 GND
    4. 7.4 Device Functional Modes
      1. 7.4.1 Board Plug-In ()
      2. 7.4.2 TIMER and PG Operation ()
      3. 7.4.3 Action of the Constant Power Engine ()
      4. 7.4.4 Response to a Hard Output Short ( and )
      5. 7.4.5 Automatic Restart ()
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Alternative Inrush Designs
        1. 8.1.1.1 Gate Capacitor (dV/dt) Control
        2. 8.1.1.2 PROG Inrush Control
      2. 8.1.2 Additional Design Considerations
        1. 8.1.2.1 Use of PG
        2. 8.1.2.2 Faults and Backplane Voltage Droop
        3. 8.1.2.3 Output Clamp Diode
        4. 8.1.2.4 Gate Clamp Diode
        5. 8.1.2.5 High Gate Capacitance Applications
        6. 8.1.2.6 Input Bypass
        7. 8.1.2.7 Output Short Circuit Measurements
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Select RSNS and CL setting
        2. 8.2.2.2 Selecting the Hot Swap FET(s)
        3. 8.2.2.3 Select Power Limit
        4. 8.2.2.4 Set Fault Timer
        5. 8.2.2.5 Check MOSFET SOA
        6. 8.2.2.6 Set Under-Voltage Threshold
        7. 8.2.2.7 Choose R5, and CIN
        8. 8.2.2.8 Input and Output Protection
        9. 8.2.2.9 Final Schematic and Component Values
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 PC Board Guidelines
      2. 10.1.2 System Considerations
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DGS|10
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.1 Design Requirements

Table 1 summarizes the design parameters that must be known before designing a hot swap circuit. When charging the output capacitor through the hot swap MOSFET, the FET’s total energy dissipation equals the total energy stored in the output capacitor (1/2CV2). Thus both the input voltage and Output capacitance will determine the stress experienced by the MOSFET. The maximum load current will drive the current limit and sense resistor selection. In addition, the maximum load current, maximum ambient temperature, and the thermal properties of the PCB (RθCA) will drive the selection of the MOSFET RDSON and the number of MOSFETs used. RθCA is a strong function of the layout and the amount of copper that is connected to the drain of the MOSFET. Note that the drain is not electrically connected to the ground plane and thus the ground plane cannot be used to help with heat dissipation. For this design example RθCA = 30°C/W is used, which is similar to the TPS2490 EVM. It’s a good practice to measure the RθCA of a given design after the physical PCBs are available.

Finally, it is important to understand what test conditions the hot swap needs to pass. In general, a hot swap is designed to pass both a Hot-Short and a Start into a Short, which are described in the previous section. Also, TI recommends to keep the load OFF until the hot swap is fully powered up. Starting the load early causes unnecessary stress on the MOSFET and could lead to MOSFET failures or a failure to start-up.

Table 1. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input voltage range 18 V - 30 V
Target UVLO Threshold 18 V
Maximum load current 10 A
Maximum Output Capacitance of the Hot swap 330 µF
Maximum Ambient Temperature 55°C
MOSFET RθCA (function of layout) 30°C/W
Pass Hot-Short on Output? Yes
Pass a Start into short? Yes
Is the load off until PG asserted? Yes
Can a hot board be plugged back in? Yes