SLVUBG8A July 2018 – December 2020 TPS23755
The TPS23755EVM-894 enables full evaluation of the TPS23755 device. Refer to the schematic shown in Figure 4-1. Ethernet power is applied from J1 and is dropped to the bridge rectifier (D1, D2). The Power over Ethernet (PoE) transformer needed to transfer power or data is T1 . The Bob Smith Terminations help balance the Ethernet cable impedance and are critical for ESD and EMI or EMC performance. The EMI or EMC filter and transient protection for the TPS23755 device are at the output of the diode bridge.
Input power can also be applied at J5 from a DC source when power at J1 is not present.
The TPS23755 (U1) PD and DC-to-DC converter circuitry is shown in Figure 4-1. R17 provides the detection signature and R20 provides the classification (class 3) signature. The switched side of the PD controller is to the right of U1. The TPS23755 RTN pin provides inrush limited turn on and charge of the bulk capacitor, C12.
The DC-to-DC converter is a high-efficiency diode rectified primary-side regulated flyback converter.
Output voltage feedback is provided with R16 and R21 on the bias winding. R14 provides a means for error injection to measure the frequency response of the converter.