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RTN

DEN

CLS

From Ethernet

Transformers

CLS

From Spare

Pairs or

Transformers

DEN

Adapter

CDB

T2P

APD

APD2

APD1

T2P

BULK

TPS2378

DC/DC Converter

DEN

CLS

T2P

CDB

RTN

APD

SO-8 PowerPad

TPS2378

www.ti.com

SLVSB99B –MARCH 2012–REVISED NOVEMBER 2013

IEEE 802.3at PoE High-Power PD Interface

Check for Samples: TPS2378

FEATURES

APPLICATIONS

• IEEE 802.3at Type-2 Hardware Classification

• IEEE 802.3at-compliant Devices

with Status Flag

• Video and VoIP Telephones

• Adapter Priority Input

• Multiband Access Points

• DC/DC Converter Enable

• Security Cameras

• Robust 100 V, 0.5 Ω Hotswap MOSFET

• Pico-base Stations

• Operating Current up to 850 mA

• Forced, Four-Pair, High Power Devices

• 1A (Typical) Operating Current Limit (SLVA625)

• 15 kV/8 kV System-level ESD Capability

• PowerPAD™ SO-8 Package

DESCRIPTION

This 8-pin integrated circuit contains all of the features needed to implement an IEEE802.3at type-2 powered

device (PD). The low 0.5 Ω internal switch resistance, combined with the enhanced thermal dissipation of the

PowerPAD™ package, enables this controller to continuously handle up to 0.85 A. The TPS2378 features an

auxiliary power detect (APD) input, providing priority for an external power adapter. It also features a 100 V pass

transistor, 140 mA inrush current limiting, type-2 indication, auto-retry fault protection, and an open-drain power-

good output.

Figure 1. Typical Application

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2PowerPAD is a trademark of Texas Instruments.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (27 pages)

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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 IEEE 802.3at PoE High-Power PD Interface Check for Samples: TPS2378 FEATURES APPLICATIONS • • • • • • • 1 2 • • • • • • • IEEE 802.3at Type-2 Hardware Classification with Status Flag Adapter Priority Input DC/DC Converter Enable Robust 100 V, 0.5 Ω Hotswap MOSFET Operating Current up to 850 mA 1A (Typical) Operating Current Limit 15 kV/8 kV System-level ESD Capability PowerPAD™ SO-8 Package IEEE 802.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range and voltages with respect to VSS (unless otherwise noted) MIN Input voltage range MAX RTN, VDD 0 57 APD to RTN 0 18 CDB, T2P to RTN 0 57 RTN Sinking current 0.85 CDB, T2P CLS (1) Resistance UNIT V A 2 mA 125 °C Ω 60 Junction temperature (1) NOM –40 Voltage should not be externally applied to this pin.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 40 V ≤ VVDD ≤ 57 V, RDEN = 24.9 kΩ, VCDB, VCLS, and VT2P open; VAPD = VRTN; –40°C ≤ TJ ≤ 125°C. Positive currents are into pins. Typical values are at 25°C. All voltages are with respect to VVSS unless otherwise noted. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Foldback deglitch time VRTN rising to when current limit changes to inrush current limit 500 800 1500 µs 0.27 0.50 V 10 μA 0.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 12V and 10V VDD 1 22V and 21.25V Detection Comp. Class Comp. 4V Class Comp. VSS 5V and 4V Mark Comp. 12V APD APD Comp. 8 2.5V REG. 800ms 800ms UVLO Comp Output RTN S R 7 T2P Q Type 2 RTN 1 = inrush 0 = current limit 6 CDB 5 RTN R S VSS CLS State Eng. Inrush latch OTSD 3 RTN Mark Comp Output UVLO Comp. DEN VSS 1.5Vand 1.2V 38.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com Table 1. Class Resistor Selection CLASS MINIMUM POWER AT PD (W) MAXIMUM POWER AT PD (W) RESISTOR RCLS (Ω) 0 1 0.44 13 1270 0.44 3.84 243 2 3.84 6.49 137 3 6.49 13 90.9 4 13 25.5 63.4 DEN (Detection and Enable): This pin implements two separate functions.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 TYPICAL CHARACTERISTICS 7 50 6 40 TA = 25°C Resistance (kΩ) IVDD (µA) 5 TA = 125°C 4 3 2 Detection Resistance 30 20 10 1 TA = −40°C 0 0 1 2 3 4 5 6 V(VDD−VSS) (V) 7 8 9 0 10 0 1 2 3 4 5 6 7 8 9 V(VDD−VSS) (V) G001 Figure 3. Detection Bias Current vs PoE Voltage 10 G002 Figure 4. Detection Resistance vs PoE Voltage 1.6 13 APD Upper Threshold 12.5 V(VDD−VSS) (V) V(ADD−RTN) (V) 1.5 1.4 1.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com 400 9.8 360 320 9.5 IVDD (µA) Mark Reset Resistance (kΩ) TYPICAL CHARACTERISTICS (continued) 10 9.2 9 TA = 25°C TA = 125°C 280 240 200 TA = −40°C 8.8 160 8.5 −50 −25 0 25 50 75 Junction Temperature (°C) 100 120 125 20 40 45 50 55 60 G009 1.02 0.6 Current Limit (A) Pass FET Resistance (Ω) 35 Figure 10. IVDD Bias Current vs Voltage 0.7 0.5 0.4 1.01 1 0.3 0.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 TYPICAL CHARACTERISTICS (continued) 38.3 32.16 32.14 V(VDD−VSS) (V) V(VDD−VSS) (V) 38.28 38.26 UVLO Rising Threshold 38.24 38.22 38.2 −50 32.12 UVLO Falling Threshold 32.1 32.08 32.06 −25 0 25 50 75 Junction Temperature (°C) 100 125 32.04 −50 G012 Figure 15. UVLO Rising Threshold vs Temperature −25 0 25 50 75 Junction Temperature (°C) 100 125 G013 Figure 16.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com DETAILED DESCRIPTION PoE OVERVIEW The following text is intended as an aid in understanding the operation of the TPS2378 but not as a substitute for the IEEE 802.3at standard. The IEEE 802.3at standard is an update to IEEE 802.3-2008 clause 33 (PoE), adding high-power options and enhanced classification. Generally speaking, a device compliant to IEEE 802.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 The PD input, typically an RJ-45 eight-lead connector, is referred to as the power interface (PI). PD input requirements differ from PSE output requirements to account for voltage drops and operating margin. The standard allots the maximum loss to the cable regardless of the actual installation to simplify implementation. IEEE 802.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com Idle Classification Type 1 Mark Type 2 Functional State PD Powered VDD-VSS Detection VCL_H VMSR VCL_ON VCU_H VUVLO_H VCU_OFF VUVLO_R Note: Variable names refer to Electrical Characteristic Table parameters Figure 18. Threshold Voltages PoE Startup Sequence Current: 100 mA/div The waveforms of Figure 19 demonstrate detection, classification, and startup from a PSE with type 2 hardware classification.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 The type 2 hardware classification protocol of IEEE 802.3at specifies that a type 2 PSE drops its output voltage into the detection range during the classification sequence. The PD is required to have an incorrect detection signature in this condition, which is referred to as a mark event (see Figure 19).
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 Idle Detect Mark Reset Mark www.ti.com Class Between Ranges Class Between Ranges Class Between Ranges UVLO Falling UVLO Rising Operating T2P open-drain TYPE 1 PSE Hardware Class PoE Startup Sequence Mark Class Between Ranges UVLO Rising Operating T2P low TYPE 2 PSE Hardware Class UVLO Falling Figure 20. Two-Event Class Internal States Inrush and Startup IEEE 802.
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TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 50 V/div VVDD-RTN Type 1 PSE 50 V/div VT2P-RTN 10 V/div VCDB-RTN Type 2 PSE PI powered Load enabled using CDB plus delay Inrush 100 mA/div IPI Time: 5 ms/div Figure 21. Power Up and Start PD Hotswap Operation IEEE 802.3at has taken a new approach to PSE output limiting. A type 2 PSE must meet an output current vs. time template with specified minimum and maximum sourcing boundaries.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com The PD control has a thermal sensor that protects the internal hotswap MOSFET. Conditions like startup or operation into a VDD-to-RTN short cause high power dissipation in the MOSFET. An over-temperature shutdown (OTSD) turns off the hotswap MOSFET and class regulator, which are restarted after the device cools. The hotswap MOSFET will be re-enabled with the inrush current limit when exiting from an over-temperature event.
PAGE 17
TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 RCLS C1 From Spare Pairs or Transformers -- DEN CLS VSS Low Voltage Output VDD VPOE D1 RDEN + Power Circuit TPS2378 From Ethernet Transformers www.ti.com RTN Adapter Option 2 Adapter Option 1 Adapter Option 3 Figure 23. Oring Configurations The IEEE standards require that the Ethernet cable be isolated from ground and all other system potentials.
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TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com APPLICATION INFORMATION Input Bridges and Schottky Diodes Using Schottky diodes instead of PN junction diodes for the PoE input bridges will reduce the power dissipation in these devices by about 30%. There are, however, some things to consider when using them. The IEEE standard specifies a maximum backfeed voltage of 2.8 V. A 100 kΩ resistor is placed between the unpowered pairs and the voltage is measured across the resistor.
PAGE 19
TPS2378 www.ti.com SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 TPS2378 UCC3809 SS CDB CSS RTN GND Figure 24. CDB Interface APD Pin Divider Network, RAPD1, RAPD2 The APD pin can be used to disable the TPS2378 internal hotswap MOSFET, giving the adapter source priority over the PoE. For an example calculation, see literature number SLVA306A. T2P Pin Interface IT2P VC RT2P IT2P-OUT The T2P pin is an active-low, open-drain output which indicates that a high power source is available.
PAGE 20
TPS2378 SLVSB99B – MARCH 2012 – REVISED NOVEMBER 2013 www.ti.com Forced, Four-Pair, High Power PoE TPS2378 can be arranged in a dual fashion to support high power, four pair operation at 51 W at the input RJ45 connector. Additional information is available in the Dual TPS2378 PD for 51 W High Power-Four Pair PoE (SLVA625) application report. ESD ESD requirements for a unit that incorporates the TPS2378 have a much broader scope and operational implications than are used in TI’s testing.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 13-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device TPS2378DDAR Package Package Pins Type Drawing SO Power PAD DDA 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 12.8 Pack Materials-Page 1 6.4 B0 (mm) K0 (mm) P1 (mm) 5.2 2.1 8.0 W Pin1 (mm) Quadrant 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 13-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TPS2378DDAR SO PowerPAD DDA 8 2500 366.0 364.0 50.
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