Power over Ethernet DC/DC controller optimised for flyback topology
The TPS23758 device from Texas Instruments combines a Power over Ethernet (PoE) powered device (PD) interface, a 150V switching power FET, and a current-mode DC/DC controller optimised for flyback topology. The PoE implementation supports the IEEE 802.3at standard as a 13-W, Type 1 PD.
The high level of integration along with primary side regulation (PSR), spread spectrum frequency dithering (SSFD), and advanced startup makes the TPS23758 an ideal solution for size-constrained applications.
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 optimised for operation in continuous conduction mode (CCM) with secondary side synchronous rectification, resulting in optimum overall efficiency, regulation accuracy and step load response over multiple outputs (for example 5 and 3.3V output). Typically, the converter operates at a switching frequency of 250kHz.
SFFD and slew rate control helps to minimise the size and cost of the EMI filter. Advanced Startup allows the use of minimal bias capacitor while simplifying converter startup and hiccup design.
Primary auxiliary power detect (APD) pin can be used to provide priority for a primary side power adapter.
The DC/DC controller features adjustable soft-start, slope compensation, and blanking. For non-isolated applications, the buck topology is also supported by the TPS23758.
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