TPS23785B

• 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.