Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsTPS2379DDA

DEN

CLS

T2P

CDB

RTN

GATE

SO-8 PowerPad

RTN

CLS

DEN

CDB

T2P

GATE

TPS2379

DEN

CLS

BLST

T2P

BULK

DC/DC Converter

From Ethernet

Transformers

From Spare

Pairs or

Transformers

TPS2379

www.ti.com

SLVSB98 –MARCH 2012

IEEE 802.3at PoE High-Power PD Interface with External Gate Driver

Check for Samples: TPS2379

FEATURES

APPLICATIONS

• IEEE 802.3at Type-2 Hardware Classification

• IEEE 802.3at-compliant Devices

with Status Flag

• Universal Power Over Ethernet (UPOE)

• Auxiliary Gate Driver for High-power Compliant Devices

Expansion

• Video and VoIP Telephones

• Robust 100 V, 0.5 Ω Hotswap MOSFET

• Multiband Access Points

• 1A (typ.) Operating Current Limit

• Security Cameras

• 140 mA (typ.) Inrush Current Limit

• Pico-Base Stations

• DC/DC Converter Enable

• 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 TPS2379 supports

higher-power applications through the use of an external pass transistor. It also features a 100 V internal pass

transistor, 140 mA inrush current, 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, PowerPAD are trademarks 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 (32 pages)

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TPS2379 www.ti.com SLVSB98 – MARCH 2012 IEEE 802.3at PoE High-Power PD Interface with External Gate Driver Check for Samples: TPS2379 FEATURES APPLICATIONS • • • 1 2 • • • • • • • IEEE 802.3at Type-2 Hardware Classification with Status Flag Auxiliary Gate Driver for High-power Expansion Robust 100 V, 0.5 Ω Hotswap MOSFET 1A (typ.) Operating Current Limit 140 mA (typ.) Inrush Current Limit DC/DC Converter Enable 15 kV/8 kV System-level ESD Capability PowerPad™ SO-8 Package IEEE 802.
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TPS2379 SLVSB98 – MARCH 2012 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. PRODUCT INFORMATION (1) DEVICE TPS2379 (1) TA PACKAGE MARKING –40°C to 85°C DDA (SO-8 PowerPAD™) 2379 For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 spacer RECOMMENDED OPERATING CONDITIONS Voltages with respect to VSS (unless otherwise noted) MIN Input voltage range Sinking current 57 T2P or CDB to RTN 0 57 RTN 0.85 CDB, T2P 2 UNIT V A mA Ω 60 Junction temperature (1) MAX 0 CLS (1) Resistance NOM RTN, VDD –40 125 °C Voltage should not be externally applied to this pin. ELECTRICAL CHARACTERISTICS 40 V ≤ VVDD ≤ 57 V, RDEN = 24.9 kΩ, CDB, CLS, GATE, T2P open; –40°C ≤ TJ ≤ 125°C.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com ELECTRICAL CHARACTERISTICS (continued) 40 V ≤ VVDD ≤ 57 V, RDEN = 24.9 kΩ, CDB, CLS, GATE, T2P open; –40°C ≤ TJ ≤ 125°C. Positive currents are into pins. Typical values are at 25°C.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 TPS2379 GATE 8 VDD PowerPAD™ 1 2 DE N 3 CLS 4 VSS T2P 7 CDB 6 RTN 5 PIN FUNCTIONS NAME NO. I/O VDD 1 I DEN 2 I/O Connect 24.9 kΩ to VDD for detection. Pull to VSS disable pass MOSFET. CLS 3 O Connect resistor from CLS to VSS to program classification current. VSS 4 RTN 5 O Drain of PoE pass MOSFET. CDB 6 O Open-drain converter disable output, active low, referenced to RTN. T2P 7 O Active low indicates type 2 PSE connected.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com DETAILED PIN DESCRIPTIONS The following descriptions refer to the schematic of Figure 1 or Figure 4 and the functional block diagram. CDB (Converter Disble Bar): This active low output is pulled to RTN when the device is in inrush current limiting, going open when inrush period has completed once the GATE output has become higher than 6 V. This ensures that the external pass transistor is enhanced before the load is enabled.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 VDD: This pin connects to the positive side of the input supply. It provides operating power to the PD controller and allows monitoring of the input line voltage. VSS: This is the input supply negative rail that serves as a local ground. The PowerPad™ must be connected to this pin to ensure proper operation. PowerPAD The PowerPad is internally connected to VSS.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) 0.7 10 Pass FET Resistance (Ω) Mark Resistance (kΩ) 9.8 9.5 9.2 9 8.8 8.5 −50 −25 0 25 50 75 Junction Temperature (°C) 100 0.6 0.5 0.4 0.3 0.2 −50 125 Figure 10. Mark Resistance vs Temperature 0 25 50 75 Junction Temperature (°C) 100 125 G008 Figure 11.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 TYPICAL CHARACTERISTICS (continued) 32.16 10 32.14 V(GATE−VSS) (V) V(VDD−VSS) (V) 9.9 32.12 UVLO Falling Threshold 32.1 32.08 Auxilary Gate Voltage 9.8 9.7 32.06 32.04 −50 −25 0 25 50 75 Junction Temperature (°C) 100 125 9.6 −50 G013 Figure 16. UVLO Falling Threshold vs Temperature −25 0 25 50 75 Junction Temperature (°C) 100 125 G015 Figure 17.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com DETAILED DESCRIPTION PoE OVERVIEW The following text is intended as an aid in understanding the operation of the TPS2379 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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TPS2379 www.ti.com SLVSB98 – MARCH 2012 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 802.3-2008 was designed to run over infrastructure including ISO/IEC 11801 class C (CAT3 per TIA/EIA568) that may have had AWG 26 conductors.
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TPS2379 SLVSB98 – MARCH 2012 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 19. Threshold Voltages PoE Startup Sequence Current: 100 mA/div The waveforms of Figure 20 demonstrate detection, classification, and startup from a PSE with type 2 hardware classification.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 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 20).
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com Idle Detect Mark Reset Mark 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 21. Two-Event Class Internal States Inrush and Startup IEEE 802.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 50V/div VVDD-RTN 10V/div V(GATE -VSS) Type 1 PSE 50V/div VT2P-RTN 10V/div VCDB-RTN PI powered Type 2 PSE Load enabled using CDB plus delay Inrush 100mA/div IPI Time: 5ms/div Figure 22. 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 versus time template with specified minimum and maximum sourcing boundaries.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com VRTN-VSS > 12V VRTN-VSS 20V/div VCDB-VSS 20V/div VGATE -VSS 5V/div Inrush 500mA/div I PI Time: 200us/div Figure 23. Response to PD Output Short Circuit Without AUX MOSFET Figure 24 shows an example of the RTN current profile during VDD to RTN short circuit when the external MOSFET is used. The circuit is depicted in Figure 1. The current will divide between the internal and external MOSFETs.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 V RTN-VSS 20V/div V RTN-VSS > 12V V GATE-VSS 5V/div Inrush 500mA/div 5A/div IINT IEXT Current limit 5A/div I PI Time: 200us/div Figure 24. Response to PD Output Short Circuit with AUX MOSFET 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.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com Auxiliary Pass MOSFET Control The TPS2379 can be used in non-standard applications requiring power significantly above the IEEE802.3at, type 2 levels. This implementation can be achieved by utilizing all four Ethernet wire pairs and boosting the TPS2379 hotswap MOSFET operating current limit. Boosting the TPS2379 operating current limit is achieved by adding an external pass MOSFET to share the total load current with the internal hotswap MOSFET.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 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.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com GATE Pin Interface A non-standard PoE system can be designed to meet extended power requirements and retain the PoE benefits such as protection of non – PoE devices and fault tolerance. Such a solution will not comply with IEEE802.3at and should be designed and operated as stand-alone system. The TPS2379 GATE pin is used to control an external pass MOSFET as shown in Figure 26. When inrush is complete, GATE sources 38µA to enable Q1, the external pass MOSFET.
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TPS2379 www.ti.com SLVSB98 – MARCH 2012 T2P Pin Interface IT2P VC RT2P IT2 P-OUT The T2P pin is an active-low, open-drain output which indicates that a high power source is available. An optocoupler can interface the T2P pin to circuitry on the secondary side of the converter. A high-gain optocoupler and a high-impedance (e.g., CMOS) receiver are recommended.
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TPS2379 SLVSB98 – MARCH 2012 www.ti.com LAYOUT Printed circuit board layout recommendations are provided in the evaluation module (EVM) documentation available for this device.
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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 TPS2379DDAR 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) TPS2379DDAR SO PowerPAD DDA 8 2500 366.0 364.0 50.
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IMPORTANT NOTICE Texas Instruments (TI) reserves the right to make changes to its products or to discontinue any semiconductor product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current and complete. TI warrants performance of its semiconductor products and related software to the specifications applicable at the time of sale in accordance with TI’s standard warranty.