DC671A

DC671A demonstration circuit provides a complete IEEE 802.3af interface and isolated 3.3V power supply solution for use in PD Phone applications. The features LTC®4257 that performs signature, classification, and power interface functions to switch power to a 48V to 3.3V isolated flyback converter featuring the LT1737. The LTC4257-1 simplifies Powered Device (PD) design by incorporating the 25kohm signature resistor, classification current source, inrush current limit, under-voltage lockout, thermal current limit, and power good signaling, all in a single 8-pin package. The LT1737 provides efficient conversion from 48V to 3.3V.

• 42V maximum turn on voltage (PD power up)
• 30V minimum turn off voltage (PD power down)
• 36V minimum operating input voltage (in from PSE)
• 57V maximum operating input voltage (in from PSE)
• 12.95W maximum input power (in from PSE)
• 350mA maximum input current (in from PSE, Vin = 37V)
• 3.3A maximum output current (Vin = 37V)
• 3.3V ±2% output voltage VOUT