Power Electronics

IEEE802.3af-Compliant Power Device Interface Controllers

Maxim Integrated Products’ new MAX5940A/MAX5940B interface controllers meet the powered device (PD) requirements of IEEE802.3af-compliant Power-over-Ethernet (LAN) systems. These ICs are ideal for power devices such as IP phones, wireless LAN access point and IP cameras. The MAX5940A/MAX5940B allow these power detectors to be safely powered over the network category-5 (CAT-5) cable.

Rated for up to +67-V operation, the MAX5940A/MAX5940B are fully compliant to the IEEE802.3af standard and are compatible with legacy power-sourcing equipment (PSE). They provide a valid 25 kΩ signature discovery and classification signature. Programmable inrush current-limit control gives these PDs the flexibility to consume more power than the maximum 13 W allocated by the IEEE802.3af standard.

During detection, both devices draw less than the 10 µA of offset current, allowing accurate detection of the 25 kΩ signature. An internal 0.6 Ω N-channel MOSFET provides isolation during detection, inrush-current control, and efficient power-mode operation.

The MAX5940A is available with a default undervoltage lockout and asserted high (PGOOD) output, while the MAX5940B is available with adjustable undervoltage lockout and choice of (PGOOD) and (PGOOD-bar) outputs to enable downstream converters. Both devices include an undervoltage-lockout deglitch filter to allow for rugged operation. The MAX5940A/MAX5940B are available in the extended temperature range (-40°C to 85°C) in a surface-mount 8-pin SO package.

For more information, visit www.maxim-ic.com.

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