Industry's First Power-over-Ethernet (PoE) Power Supply that Integrates an 802.3af PD Interface, PWM Controller, and Power MOSFETs
SUNNYVALE, CA-April 21, 2006-Maxim Integrated Products (NASDAQ: MXIM) introduces the MAX5953. The MAX5953 is the industry's first fully integrated 802.3af powered-device (PD) interface with a pulse-width-modulation (PWM) controller and power MOSFETs. The device is targeted at isolated power supplies for IEEE802.3af-compliant, Power-over-Ethernet (PoE) PDs such as IP Phones, WLAN access points, and IP cameras.
The MAX5953 provides 802.3af PDs with a detection signature, a classification signature, and an integrated power MOSFET with programmable inrush-current control. During detection, the device draws less than the 10µA of offset current, thus allowing accurate detection of the 25kΩ signature. This power supply also features power-mode undervoltage lockout (UVLO) with wide hysteresis and long deglitch time, both to compensate for twisted-pair-cable resistive drop and to ensure glitch-free transition between detection, classification, and power-on/-off phases.
The integrated PWM IC also has integrated power MOSFETs that can be configured for either forward or flyback configurations. The PWM features a wide input-voltage range from 11V to 76V, and up to 15W of output power.
The MAX5953 provides a 'look-ahead' signal for driving secondary-
side synchronous rectifiers. This feature allows greater than 90% efficiency without resorting to complicated drive schemes and additional discrete components. The device provides continuous short-circuit protection with a hiccup-mode current limit, which reduces power dissipation under persistent overload conditions. The switching frequency is resistor-/capacitor-programmable up to 500kHz, allowing the use of smaller magnetics and capacitors.
Rated for operation over the industrial temperature range (-40°C to +85°C), the MAX5953 is available in a thermally enhanced 48-pin TQFN package capable of dissipating up to 2.22W. Prices start at $2.56 (1000-up, FOB USA).
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