IEEE 802.3af Power-Supply IC Integrates Power MOSFETs, Reducing Power-Supply Size and Cost for POE
SUNNYVALE, CA-August 5, 2004-Maxim Integrated Products (NASDAQ: MXIM) introduces the MAX5074, a pulse-width-modulation (PWM) power IC with integrated power MOSFETs. The device is targeted at isolated power supplies for IEEE 802.3af-compliant, power-over-Ethernet (POE), powered devices (PDs) such as IP phones, WLAN access points, and IP cameras. The MAX5074 is also ideal for converting -48V to +3.3V in power-sourcing equipment (POE), which includes switch/routers and midspans. The device can be used in both flyback- and forward-converter isolated power supplies with a wide ±11V to ±76V input-voltage range and up to 15W output power.
The MAX5074 provides a "look ahead" signal for driving secondary-side synchronous rectifiers, thus allowing greater than 90% efficiency without resorting to complicated drive schemes and additional discrete components. The device includes thermal shutdown. It provides continuous short-circuit protection with hiccup-mode current limit, which reduces power dissipation under persistent overload conditions. The switching frequency is resistor-/capacitor-programmable up to 500kHz, thus allowing the use of smaller external magnetics and capacitors. These features, together with the integrated MOSFETs, reduce power-supply size and cost for POE applications.
Rated for operation over a wide -40 degrees Celsius to +125 degrees Celsius temperature range, the MAX5074 is available in a thermally enhanced 20-pin TSSOP package capable of dissipating up to 1.74W at 70 degrees Celsius ambient temperature. Prices start at $1.44 (1000-up, FOB USA).
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