Analog Devices LT4275/LT4321 | Demoboard DC2093A-A

Description

Demonstration circuit 2093A features the LT®4275, a fourth generation powered device (PD) controller and the LT4321, an ideal diode bridge controller for Power over Ethernet (PoE) applications.

The DC2093A is available in DC2093A-A, DC2093A-B, and DC2093A-C versions to meet the power level required by the PD application. The DC2093A-A features the LT4275A PD controller. This controller supports the IEEE 802.3at(Type 2, PoE+), IEEE 802.3af (Type 1, PoE) and LTPoE++™ specifications. LTPoE++ adds four power levels to the existing IEEE standard with 38.7W, 52.7W, 70W, and 90W of delivered PD power at the RJ45 jack. The DC2093A-B features the LT4275B PD controller and is compliant withthe IEEE 802.3at and IEEE 802.3af specifications. The DC2093A-C features the LT4275C PD controller and is compliant with the IEEE 802.3af specification.

All three assemblies of the DC2093A include a PoE ideal diode bridge controller, LT4321, and eight N-channel FETs to reduce heat, maximize power efficiency, and increase delivered power compared to a conventional diode bridge rectifier. This controller is designed to be used in PoE applicationswithout corrupting the PD’s signature resistance during detection and prevent reverse current during a short at the Ethernet cable.

Many of the main features from the previous generation PD controller are included in the LT4275 PD controller. These include a power good indicator, a power sourcing equipment (PSE) type indicator, and support for an auxiliary power input. The major difference from the previous generation PD controller is that the LT4275 drives an external N-channel Hot Swap™ FET at the PoE high side voltage rail. This allows the user to choose a low RDS(ON)N-channel MOSFE to maximize power efficiency, reduce heat dissipation, and ease thermal design. An LED status indicator is included to indicate that the Hot Swap FET is fully turned on and the PSE is powering the PD. A sufficient load to sink more than 10mA is also included to assure the PSE maintains power to the PD and to meet the DC maintain power signature current required by the IEEE 802.3at/IEEE 802.3af specification.

Simply connect the output of the DC2093A to the DC/DC converter that is right for the application. Linear Technology offers a variety of DC/DC converter solutions that can be used with the DC2093A (eg DC894, DC1317, etc).

More information

• Datasheet
• IC product information