IEEE 802.3bt type 3 class 1-4 PoE PD with no-opto flyback DC-DC controller

The TPS23731 device

combines a Power over Ethernet (PoE) powered device (PD) interface, and a

current-mode DC-DC controller optimized for flyback switching regulator designs where the use of primary-side regulation (PSR) is

supported. The PoE interface supports the IEEE 802.3bt and IEEE 802.3at

standard s for

applications needing up to 25.5 W or less at PD

input.

Programmable spread spectrum frequency

dithering (SSFD) is provided to minimize the size and cost of EMI filter. Advanced

Startup with adjustable soft-start helps to use minimal bias capacitor while

simplifying converter startup and hiccup design, also ensuring that IEEE 802.3bt /at startup

requirements are met.

The soft-stop feature minimizes stress

on switching

sync FET(s), allowing FET BOM cost

reduction.

The PSR feature of the DC-DC

controller uses feedback from an auxiliary winding for control of the output

voltage, eliminating the need for external shunt regulator and optocoupler. It is

optimized for continuous conduction mode (CCM), and can work with secondary side

synchronous rectification, resulting in optimum efficiency, regulation accuracy and

step load response over multiple outputs.

The DC-DC controller features slope

compensation and blanking. Typical switching frequency is 250 kHz.

The automatic MPS enables applications

with low power modes or multiple power feeds. It automatically adjusts its pulsed

current amplitude and duration according to PSE Type and system conditions, to

maintain power while minimizing consumption.