SLUSCM4B October   2017  – November 2018 TPS2372

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simplified Schematic
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin 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 PG Power Good (Converter Enable) Pin Interface
      2. 7.3.2 CLSA and CLSB Classification, AUTCLS
      3. 7.3.3 DEN Detection and Enable
      4. 7.3.4 Internal Pass MOSFET and Inrush Delay Enable, IRSHDL_EN
      5. 7.3.5 TPH, TPL and BT PSE Type Indicators
      6. 7.3.6 AMPS_CTL, MPS_DUTY and Automatic MPS
      7. 7.3.7 VDD Supply Voltage
      8. 7.3.8 VSS
      9. 7.3.9 Exposed Thermal PAD
    4. 7.4 Device Functional Modes
      1. 7.4.1  PoE Overview
      2. 7.4.2  Threshold Voltages
      3. 7.4.3  PoE Startup Sequence
      4. 7.4.4  Detection
      5. 7.4.5  Hardware Classification
      6. 7.4.6  Autoclass
      7. 7.4.7  Inrush and Startup
      8. 7.4.8  Maintain Power Signature
      9. 7.4.9  Startup and Converter Operation
      10. 7.4.10 PD Hotswap Operation
      11. 7.4.11 Startup and Power Management, PG and TPH, TPL, BT
      12. 7.4.12 Using DEN to Disable PoE
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Requirements
        1. 8.2.2.1  Input Bridges and Schottky Diodes
        2. 8.2.2.2  Protection, D1
        3. 8.2.2.3  Capacitor, C1
        4. 8.2.2.4  Detection Resistor, RDEN
        5. 8.2.2.5  Classification Resistors, RCLSA and RCLSB
        6. 8.2.2.6  Opto-isolators for TPH, TPL and BT
        7. 8.2.2.7  Automatic MPS and MPS Duty Cycle, RMPS and RMPS_DUTY
        8. 8.2.2.8  Internal Voltage Reference, RREF
        9. 8.2.2.9  Autoclass
        10. 8.2.2.10 Inrush Delay
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 EMI Containment
    4. 10.4 Thermal Considerations and OTSD
    5. 10.5 ESD
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Links
      2. 11.1.2 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGW|20
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Opto-isolators for TPH, TPL and BT

The TPH, TPL and BT pin are active-low, open-drain outputs, which give an indication about the PSE allocated power along with its Type. Optocouplers can interface these pins to circuitry on the secondary side of the converter. A high-gain optocoupler and a high-impedance (for example, CMOS) receiver are recommended. Design of the optocoupler interface can be accomplished as follows:

TPS2372 tph_tpl_bt_intface_SLUSCM4.gif
See Table 2 to decode PSE Type
Figure 23. TPH, TPL, and BT Interface
  1. As shown in Figure 23, let VDD = 48 V, VOUT = 5 V, RTPx–OUT = 10 kΩ, VTPx = 260 mV, VTPx-OUT = 400 mV.
  2. Equation 1. TPS2372 eq_it2p_out_SLUSCD1.gif
  3. The optocoupler current transfer ratio, CTR, is needed to determine RTPx. A device with a minimum CTR of 100% at 1 mA LED bias current, ITPx, is selected. In practice, CTR will vary with temperature, LED bias current, and aging, These variations may require some iteration using the CTR-versus-IDIODE curve on the optocoupler data sheet.
    1. The approximate forward voltage of the optocoupler diode, VFWLED, is 1.1 V from the data sheet.
    2. Use .
    3. Equation 2. TPS2372 eq_rtpx_SLUSCM4.gif
    4. Choose a 46.4 kΩ resistor.

Most applications require that only the PSE’s allocated power information (TPH and TPL) is needed for the MCU or PD load. In this case, the circuitry needed to drive the BT signal is not necessary and the BT pin can be left floating.

Some applications such as PoE lighting can benefit from the BT signal to show that the power consumption in standby operation may not meet regulatory requirements. In non-standard PoE applications, BT is used with TPH and TPL to indicate a PoE++ PSE.