1 Features

• Powers up to 30-W (Input) PDs

• DC-DC Control Optimized for Isolated Converters

• Supports High-Efficiency Topologies

• Complete PoE Interface

• Enhanced Classification per IEEE 802.3at With

Status Flag

• Adapter ORing Support

• Programmable Frequency With Synchronization

• Robust 100-V, 0.5-Ω Hotswap MOSFET

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

• Industry Standard PowerPAD™ HTSSOP-20

2 Applications

• IEEE 802.3at Compliant Devices

• Video and VoIP Telephones

• RFID Readers

• Multiband Access Points

• Security Cameras

3 Description

The TPS23754 and TPS23756 devices have a

combined power-over-ethernet (PoE), powereddevice

(PD) interface, and current-mode DC-DC

controller optimized specifically for isolated

converters. The PoE interface supports the IEEE

802.3at standard.

The TPS23754 and TPS23756 support 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 new extended

hardware 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-DC controller features two complementary

gate drivers with programmable dead time. This

simplifies the design of active-clamp forward

converters or optimized gate drive for highly-efficient

flyback topologies. The second gate driver may be

disabled if desired for single MOSFET topologies.

The controller also features internal soft start,

bootstrap start-up 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 TPS23754 device has a 15-V converter start-up

while the TPS23756 device has a 9-V converter startup.

The TPS23754-1 replaces the PPD pin with a noconnect

for increased pin spacing.