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TPS23785B

ACTIVE

High-Power, High-Efficiency PoE PD and DC-to-DC Controller

Product details

Vin (min) (V) 15.7 Vin (max) (V) 57 PoE current limit (min) (mA) 850 PoE inrush limit (mA) (typ) (A) 0.14 rDS(on) per FET (typ) (mΩ) 430 PoE standards supported 802.3at Type 1 (802.3af), 802.3at Type 2 PD power level 13W, 25W DC/DC control PD and DC/DC Fault response Auto Retry Features Second Gate Drive, Thermal shutdown Operating temperature range (°C) -40 to 125 Rating Catalog
Vin (min) (V) 15.7 Vin (max) (V) 57 PoE current limit (min) (mA) 850 PoE inrush limit (mA) (typ) (A) 0.14 rDS(on) per FET (typ) (mΩ) 430 PoE standards supported 802.3at Type 1 (802.3af), 802.3at Type 2 PD power level 13W, 25W DC/DC control PD and DC/DC Fault response Auto Retry Features Second Gate Drive, Thermal shutdown Operating temperature range (°C) -40 to 125 Rating Catalog
HTSSOP (PWP) 24 49.92 mm² 7.8 x 6.4
  • Powers up to 30-W (Input) PDs
  • DC-to-DC Control Optimized for Non-Isolated Converters
  • Supports High-Efficiency Topologies
  • Complete PoE Interface
  • Enhanced Classification per IEEE 802.3at with Status Flag
  • Adapter ORing Support
  • Robust 100-V, 0.5-Ω Hotswap MOSFET
  • –40°C to 125°C Junction Temperature Range
  • Industry Standard PowerPAD TSSOP-24
  • Powers up to 30-W (Input) PDs
  • DC-to-DC Control Optimized for Non-Isolated Converters
  • Supports High-Efficiency Topologies
  • Complete PoE Interface
  • Enhanced Classification per IEEE 802.3at with Status Flag
  • Adapter ORing Support
  • Robust 100-V, 0.5-Ω Hotswap MOSFET
  • –40°C to 125°C Junction Temperature Range
  • Industry Standard PowerPAD TSSOP-24

The TPS23785B is a combined Power over Ethernet (PoE) powered device (PD) interface and current-mode DC-to-DC controller optimized specifically for non-isolated converters. The PoE interface supports the IEEE 802.3at standard.

The TPS23785B supports a number of input voltage ORing options including highest voltage, external adapter preference, and PoE preference. These features allow the designer to determine which power source will carry the load under all conditions.

The PoE interface features the two-event, physical-layer classification necessary for compatibility with high-power midspan power sourcing equipment (PSE) per IEEE 802.3at. The detection signature pin can also be used to force power from the PoE source off. Classification can be programmed to any of the defined types with a single resistor.

The DC-to-DC controller features two complementary gate drivers with programmable dead time. This simplifies design for highly-efficient flyback topologies utilizing secondary synchronous rectification. The second gate driver may be disabled if desired for single MOSFET topologies. The controller also features internal softstart, bootstrap startup source, current-mode compensation, and a 78% maximum duty cycle. A programmable and synchronizable oscillator allows design optimization for efficiency and eases use of the controller to upgrade existing power supply designs. Accurate programmable blanking, with a default period, simplifies the usual current-sense filter design trade-offs.

The TPS23785B is a combined Power over Ethernet (PoE) powered device (PD) interface and current-mode DC-to-DC controller optimized specifically for non-isolated converters. The PoE interface supports the IEEE 802.3at standard.

The TPS23785B supports a number of input voltage ORing options including highest voltage, external adapter preference, and PoE preference. These features allow the designer to determine which power source will carry the load under all conditions.

The PoE interface features the two-event, physical-layer classification necessary for compatibility with high-power midspan power sourcing equipment (PSE) per IEEE 802.3at. The detection signature pin can also be used to force power from the PoE source off. Classification can be programmed to any of the defined types with a single resistor.

The DC-to-DC controller features two complementary gate drivers with programmable dead time. This simplifies design for highly-efficient flyback topologies utilizing secondary synchronous rectification. The second gate driver may be disabled if desired for single MOSFET topologies. The controller also features internal softstart, bootstrap startup source, current-mode compensation, and a 78% maximum duty cycle. A programmable and synchronizable oscillator allows design optimization for efficiency and eases use of the controller to upgrade existing power supply designs. Accurate programmable blanking, with a default period, simplifies the usual current-sense filter design trade-offs.

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Active – Limited TI design support

This product has limited direct TI design support for existing projects. If available, you can find relevant collateral and software on the product folder. For existing designs using this product, you may request support in the TI E2E support forums, but limited support is available for this product.

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Technical documentation

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Type Title Date
* Data sheet High-Power, High-Efficiency PoE PD and DC-to-DC Controller datasheet (Rev. A) 18 Dec 2012
Application note Lightning Surge Considerations for PoE Powered Devices 30 Apr 2015
User guide TPS23785BEVM-522 Evaluation Module 25 Apr 2014
Application note Efficiency-Optimized, Synchronous Flyback, High-Power PoE Controller/Converter 17 Jan 2012
Application note High Efficiency Class 4 PoE Powered Device 23 Mar 2011
Application note Advanced Adapter ORing Solutions using the TPS23753 (Rev. A) 09 Feb 2009
Application note Designing an EMI Compliant PoE with Isolated Flyback 20 May 2008

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Calculation tool

SLUC480 PoE PD Efficiency Calculator

Supported products & hardware

Supported products & hardware

Products
Powered devices
TPS2375 Class 3 PoE PD with latch protection TPS23750 Class 3 PoE PD with flyback DC-DC controller TPS23751 IEEE 802.3at PoE interface with flyback DC-DC controller TPS23752 IEEE 802.3at PoE interface with flyback DC-DC controller and Sleep Mode Feature TPS23753 IEEE 802.3-2005 PoE Interface and Isolated Converter and Controller TPS23753A IEEE 802.3-2005 PoE interface and Isolated Converter controller with Enhanced ESD Ride-Through TPS23754 IEEE 802.3at, high efficiency, PoE interface and DC/DC controller TPS23754-1 IEEE 802.3at PoE interface and isolated converter controller TPS23756 Class 4 PoE PD with flyback/forward DC-DC controller & 12V-57V adapter support TPS23757 Class 3 PoE PD with flyback/Forward DC-DC controller & 12V-57V Adapter Support TPS2376 Class 3 PoE PD with adjustable UVLO threshold & latch protection TPS2377 Class 3 PoE PD with legacy UVLO threshold & latch protection TPS2378 IEEE 802.3at PoE High-Power PD interface with AUX Control TPS23785B High-Power, High-Efficiency PoE PD and DC-to-DC Controller TPS2379 IEEE 802.3at PoE High-Power PD interface with external gate driver
Simulation tool

PSPICE-FOR-TI — PSpice® for TI design and simulation tool

PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
Reference designs

PMP8408 — Class 3 - Mulitple Output, High Efficiency Driven Flyback Converter for PoE Applications

This converter is used for Class 3 PoE applications where high efficiency and multiple outputs are required. The flyback converter with synchronous rectifier provides excellent efficiency and small size for PoE applications such as IP Phones. The TPS23785B contains both the PoE Powered Device (...)
Test report: PDF
Schematic: PDF
Reference designs

PMP8454 — Class 3 - Mulitple Output, High Efficiency Self-Driven Flyback Converter for PoE Applications

This converter is used for Class 3 PoE applications where high efficiency and multiple outputs are required. PMP8454.1 has an output of 3.3V@2A. The flyback converter with synchronous rectifier provides excellent efficiency and small size for PoE applications such as a IP Phones. The TPS23785B (...)
Test report: PDF
Reference designs

PMP8752 — Class 1 Mulitple Output High Efficiency Flyback Converter for PoE Applications Reference Design

This converter is used for Class 1 PoE applications where high-efficiency and multiple-outputs are required. The multi-outputs for this design are 3.3V/0.7A, 5V/0.145A, 3.3V/1.5A. The flyback converter with synchronous rectifier provides excellent efficiency, and small size for PoE applications, (...)
Test report: PDF
Schematic: PDF
Reference designs

PMP8407 — Class 2 Mulitple Output, High Efficiency Flyback Converter for PoE Applications

This reference evaluation module, featuring the TPS23785B PoE interface and DC-toDC contoller, is used for class 2 PoE applications where high effliency and multiple outputs are required.

The flyback converter with synchronous reftifier provides excellent efficiency and small size for PoE (...)

Test report: PDF
Schematic: PDF
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