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TPS23753

OUT

GATE

RTN

CTL

58V

0.1µF

DEN

CLS

From Ethernet

Transformers

DD1

CLS

OUT

CTL

From Spare

Pairs or

Transformers

DEN

BLNK

FRS

Adapter

FBU

FBL

TLV431

APD

APD2

APD1

BLNK

BR1

BR2

* AdapterinterfaceandR

BLNK

areOptional

TPS23753

www.ti.com

SLVS853C –JUNE 2008–REVISED JANUARY 2010

IEEE 802.3 PoE INTERFACE AND ISOLATED CONVERTER CONTROLLER

Check for Samples: TPS23753

FEATURES

DESCRIPTION

• Optimized for Isolated Converters

• Complete PoE Interface

The TPS23753 is a combined Power over Ethernet

(PoE) powered device (PD) interface and

• Adapter ORing Support

current-mode dc/dc controller optimized specifically

• 12 V Adapter Support

for isolated converter designs. The PoE

• Programmable Frequency with Synch.

implementation supports the IEEE 802.3at standard

as a 13 W, type 1 PD. The requirements for an IEEE

• Robust 100 V, 0.7 Ω Hotswap MOSFET

802.3at type 1 device are a superset of IEEE

• Small TSSOP 14 Package

802.3-2008 (originally 802.3af) requirements.

• 15 kV / 8 kV System Level ESD Capable

The TPS23753 supports a number of input-voltage

• –40°C to 125°C Junction Temperature Range

ORing options including highest voltage, external

• Design Procedure Application Note - SLVA305

adapter preference, and PoE preference.

• Adapter ORing Application Note - SLVA306

The PoE interface features an external detection

signature pin that can also be used to disable the

APPLICATIONS

internal hotswap MOSFET. This allows the PoE

function to be turned off. Classification can be

• IEEE 802.3at Compliant Powered Devices

programmed to any of the defined types with a single

• VoIP Telephones

resistor.

• Access Points

The dc/dc controller features a bootstrap startup

• Security Cameras

mechanism with an internal, switched current source.

This provides the advantages of cycling overload fault

protection without the constant power loss of a pull up

resistor.

The programmable oscillator may be synchronized to

a higher-frequency external timing reference.

Figure 1. Basic TPS23753 Implementation

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.

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 (31 pages)

PAGE 1
TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 IEEE 802.3 PoE INTERFACE AND ISOLATED CONVERTER CONTROLLER Check for Samples: TPS23753 FEATURES 1 • • • • • • • • • • • DESCRIPTION Optimized for Isolated Converters Complete PoE Interface Adapter ORing Support 12 V Adapter Support Programmable Frequency with Synch. Robust 100 V, 0.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure.
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TPS23753 www.ti.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Unless otherwise noted: CS = APD = CTL = RTN, GATE open, RFRS = 60.4 kΩ, RBLNK = 249 kΩ, CVB = CVC = 0.1 μF, RDEN = 24.9 kΩ, RCLS open, VVDD-VSS = 48 V, VVDD1-RTN = 48 V, 8.5 V ≤ VVC-RTN ≤ 18 V, –40°C ≤ TJ ≤ 125°C Controller Section Only [VSS = RTN and VDD = VDD1] or [VSS = RTN = VDD], all voltages referred to RTN. Typical specifications are at 25°C.
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TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 ELECTRICAL CHARACTERISTICS (continued) PoE and Control [VDD = VDD1] or [VDD1] = RTN, VVC-RTN = 0 V, all voltages referred to VSS. Typical specifications are at 25°C. PARAMETER TEST CONDITIONS RTN (PASS DEVICE) MIN TYP 0.7 1.2 Ω 450 505 mA mA On resistance Ilkg MAX UNIT (VDD1 = RTN) Current limit VRTN = 1.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com VC VDD1 Oscillator FRS CTL enb 800ms Soft Start 50kW CONV. OFF enb + 1 0.75V enb 40mA (pk) 2.875kW GATE D Q CK + 50kW Control CLRB RTN Blank Switch Matrix CS Converter Thermal Monitor + Regulator VB Reference - 0.55V RTN 1.5V & 1.2V APDb BLNK VDD 11.5V & 9.5V Class Regulator AUXb APD CLS 2.53V 22V & 21.25V 12.5V & 1V V SS DEN 400ms Common Circuits and PoE Thermal Monitor S Q R 35V & 30.5V CONV.
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TPS23753 www.ti.com VADPTR _ OFF = SLVS853C – JUNE 2008 – REVISED JANUARY 2010 RAPD1 + RAPD 2 RAPD 2 ⋅ (VAPDEN − VAPDH ) (2) The CLS output is disabled when a voltage above VAPDEN is applied to the APD pin. Place the APD pull-down resistor adjacent to the APD pin. APD should be tied to RTN when not used. BLNK Blanking provides an interval between the gate drive going high and the current comparator on CS actively monitoring the input.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com FRS Connect a resistor from FRS to RTN to program the converter switching frequency. Select the resistor per the following relationship. RFRS ( k Ω ) = 15000 fSW ( kHz ) (4) The converter may be synchronized to a frequency above its maximum free-running frequency by applying short ac-coupled pulses into the FRS pin. More information is provided in the Applications section. The FRS pin is high impedance.
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TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 TYPICAL CHARACTERISTICS DETECTION BIAS CURRENT vs VOLTAGE PoE CURRENT LIMIT vs TEMPERATURE 458 8 7 456 PoE - Current Limit - mA IVDD - Bias Current - mA 6 TJ = 125°C 5 4 3 TJ = 25°C 2 454 452 450 448 1 TJ = -40°C 0 0 2 6 VVDD-VSS - PoE Voltage - V 4 446 -40 10 8 20 40 60 80 TJ - Junction Temperature - °C Figure 4. CONVERTER START TIME vs TEMPERATURE CONVERTER STARTUP SOURCE CURRENT vs VVDD1 120 6 VVC = 8.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.
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TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 TYPICAL CHARACTERISTICS (continued) MAXIMUM DUTY CYCLE vs TEMPERATURE CURRENT SLOPE COMPENSATION VOLTAGE vs TEMPERATURE 124 RFRS = 301 kW (50 kHz) 78 RFRS = 148.5 kW (100 kHz) 77.5 RFRS = 60.4 kW (250 kHz) 77 RFRS = 30.1 kW (500 kHz) 76.5 76 -40 -20 0 60 80 20 40 TJ - Junction Temperature - °C 100 120 118 116 114 -40 120 -20 0 20 40 60 Figure 11. Figure 12.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com TYPICAL CHARACTERISTICS (continued) 450 18 400 14 350 10 300 6 250 2 200 -2 150 -6 100 -10 50 -14 0 0 50 100 150 200 250 RBLNK - kW 300 350 Difference from Computed - ns Blanking Period - ns BLANKING PERIOD vs RBLNK -18 400 Figure 15.
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TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 APPLICATIONS Classic PoE Overview The following text is intended as an aid in understanding the operation of the TPS23753 but not as a substitute for the actual 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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TPS23753 Operational State SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com PD Powered Idle Classification VVDD-VSS Detection VCL_HYS 1.4V VCL_ON VUVLO_H VCU_HYS VUVLO_R VCU_OFF Note: Variable names refer to Electrical Characteristic Table parameters Figure 17. Threshold Voltages PoE Startup Sequence The waveforms of Figure 18 demonstrate detection, classification, and startup from a type 1 PSE. The key waveforms shown are VVDD-VSS, VRTN-VSS, and IPI. IEEE 802.
PAGE 15
TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 The detection resistance seen by the PSE at the PI is the result of the input bridge resistance in series with the parallel combination of RDEN and the TPS23753 bias loading. The input diode bridge’s incremental resistance may be hundreds of Ohms at the very low currents drawn when 2.7 V is applied to the PI. The input bridge resistance is partially cancelled by the TPS23753's effective resistance during detection.
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TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com Converter switching is allowed if the PD is not in inrush and the VC under-voltage lock out (UVLO) permits it. Continuing the startup sequence shown in Figure 19, VVC rises as the startup current source charges CVC and M1 switching is inhibited by the status of the VC UVLO. The VB regulator powers the internal converter circuits as VVC rises.
PAGE 17
TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 Figure 20. Response to PSE Step Voltage 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 overtemperature shutdown (OTSD) turns off the hotswap MOSFET and class regulator, which are restarted after the device cools.
PAGE 18
TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com Care in design of the transformer and VC bias circuit is required to obtain hiccup overload protection. Leading-edge voltage overshoot on the bias winding may cause VC to peak-charge, preventing the expected tracking with output voltage. RVC (Figure 1) is often required slow the peak charging. Good transformer bias-to-output-winding coupling results in reduced overshoot and better voltage tracking.
PAGE 19
TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 Thermal Considerations Sources of nearby local PCB heating should be considered during the thermal design. Typical calculations assume that the TPS23753 is the only heat source contributing to the PCB temperature rise. It is possible for a normally operating TPS23753 device to experience an OTSD event if it is excessively heated by a nearby device.
PAGE 20
TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com RTN GATE 5/09/08 CS RS RCS CS Figure 22. Additional Slope Compensation CS may be required if the presence of RS causes increased noise, due to adjacent signals like the gate drive, to appear at the CS pin. The TPS23753 has an internal pull-down on CS ( ~500 Ω ) while the MOSFET is OFF to reduce cycle-to-cycle carry-over voltage on CS.
PAGE 21
TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 diode ORing external power into a PD. Only one option would be used in any particular design. Option 1 applies power to the TPS23753 PoE input, option 2 applies power between the TPS23753 PoE section and the power circuit, and option 3 applies power to the output side of the converter. Each of these options has advantages and disadvantages.
PAGE 22
TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com The least popular technique is PoE priority. It is implemented by placing a diode between the PD supply voltage, VDD, and the dc/dc controller bias voltage, VDD1. The diode prevents reverse biasing of the PoE input diode bridges when option 2 adapter ORing is used. The PSE may then detect, classify, and provide power to the PD while a live adapter is connected.
PAGE 23
TPS23753 www.ti.com SLVS853C – JUNE 2008 – REVISED JANUARY 2010 Occasionally, a technique referred to as frequency dithering is utilized to provide additional EMI measurement reduction. The switching frequency is modulated to spread the narrowband individual harmonics across a wider bandwidth, thus lowering peak measurements. The circuit of Figure 26 modulates the switching frequency by feeding a small ac signal into the FRS pin. These values may be adapted to suit individual needs. 10kΩ 49.
PAGE 24
TPS23753 SLVS853C – JUNE 2008 – REVISED JANUARY 2010 www.ti.com REVISION HISTORY Changes from Original (June 2008) to Revision A Page • Changed data sheet From: Product Preview To: Production ............................................................................................... 1 • Changed the TPS23753 Functional Block Diagram. ............................................................................................................ 6 • Added the Typical Characteristics section. ........
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Jan-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device TPS23753PWR Package Package Pins Type Drawing TSSOP PW 14 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 12.4 Pack Materials-Page 1 6.9 B0 (mm) K0 (mm) P1 (mm) 5.6 1.6 8.0 W Pin1 (mm) Quadrant 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Jan-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TPS23753PWR TSSOP PW 14 2000 367.0 367.0 35.
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