4

dc1843bfa

DEMO MANUAL DC1843B

DEMONSTRATION CIRCUIT 1842B OPERATION

Figure 5. DC1842B 8-Port PSE Daughter Card with Digital Isolation Features the LTC4290B and LTC4271

8-Port PSE Daughter Card with Digital Isolation

Demonstration circuit 1842B (Figure 5) features the

LTC4290B/LTC4271 chipset on a compact daughter card

with digital isolation. The LTC4290B/LTC4271 chipset is

an 8-port power sourcing equipment (PSE) controller

designed for use in IEEE 802.3at Type 1 and Type 2 (high

power) compliant Power over Ethernet (PoE) systems. A

transformer isolated communication protocol replaces

expensiveopto-couplersandcomplexisolated3.3Vsupply

resulting in significant BOM cost savings. The LTC4290B/

LTC4271 chipset delivers lowest-in-industry heat dissipa-

resistors, eliminating the need for expensive heat sinks.

Advanced power management features in the LTC4290B/

LTC4271 chipset include: per port 12-bit current monitor-

ing ADCs, DAC programmable current limit, and versatile

quick shutdown of preselected ports. PD discovery uses a

proprietarydualmode4-pointdetectionmechanismensur-

ing excellent immunity from false PD detection. Midspan

PSEs are supported with 2-event classification and a two

second backoff timer. The LTC4290B/LTC4271 includes

The DC1842B demonstrates proper LTC4290B/LTC4271

board layout that is approximately the height and width

of a 2 × 4 RJ45 connector. The compact layout is made

possiblebythesmallpackagesizeofkeycomponents.The

LTC4290B is in a 6mm × 6mm QFN, while the LTC4271 is

in a 4mm × 4mm QFN. Each port has a PSMN075-100MSE

MOSFET in a 3mm × 3mm LFPAK33 package.

The daughter card inserts in the DC1680B motherboard

through J1, a polarized 30-pin connector. Isolated 3.3V

and logic control signals are brought in on this connec-

motherboard and 8 PSE controlled outputs.