DC859A

DC859A demonstration circuit is a multiple output PD featuring the LTC4267. The board provides a complete IEEE 802.3af power device (PD) interface and isolated power supply solution for use in Power over Ethernet (PoE) applications. It generates 1.8V at 2.5A, 2.5V at 1.5A and 3.3V at 0.5A. The LTC4267 integrates the 25kohm signature resistor, classification current source, thermal overload protection, signature disable and power good signal along with an undervoltage lockout optimized for use with the IEEE required diode bridge. The precision dual level input current limit allows the LTC4267 to charge load capacitors and interface with legacy PoE systems. The LTC4267 combines the above features with a current mode switching controller designed for driving a 6V rated N-channel MOSFET. It features programmable slope compensation, soft-start, and constant frequency operation, minimizing electrical noise even with light loads.

• Turn-on voltage of -36V maximum (input from PSE )
• Maximum turn-off voltage of -32V (input from PSE, PD switch turns off)
• Power converter input operating range from -37V to -57V at VOUT =3.3V, IOUT = 0 to 2.6A
• 0.5A maximum output current at VOUT3 =3.3V
• 3.3V, typical output voltage at VIN =48V DC from PSE
• ±2% output regulation at VOUT2 = 2.5V, VIN = -37 to -57V DC, zero to full load