Dallas—Texas Instruments' third generation power-over-Ethernet device, the TPS23750, combines the functionality of the company's TPS2375 powered device (PD) controller with a primary side DC/DC pulse-width modulation (PWM) controller. Thus it effectively manages device discovery and classification as well as delivery of direct-current (DC) power to an end appliance to ease implementation of Ethernet-powered systems such as IP phones, security networks, and RFID scanners. Relatively few external components are required.
The chip, housed in a PowerPad package with an internal 0.7-ohm FET to minimize heat dissipation issues, can support isolated or non-isolated power supply topologies including flyback, forward, and non-synchronous low-side buck designs. Switching frequency is set by an external resistor. In-rush current limit is set at 140 mA to ease powered device startup. Protection features include programmable soft start, hiccup-type fault limiting, a 50 percent maximum duty cycle, and a true-voltage output error amplifier.
The TPS23750 can withstand transients to 100 volts. The chip carries includes thermal-shutdown and current-limiting protection circuitry. To meet the power requirements of certain legacy systems not fully 802.3af-compliant, TI also announced its TPS23770 integrated PD controller. It's basically the same device as the TPS23750 with the exception of its under-voltage lockout turn-on voltage, which is designed to be compatible with legacy systems.
The device datasheet can be secured by clicking here. The TPS23750 and TPS23770 controllers are both available now in volume. The devices, which come in a 20-pin high-power, thin shrink small outline package (HTTSOP), carry a suggested resale price of $1.75 each in quantities of 1k units. Evaluation modules of the TPS23750 and TPS23770, complete reference designs, application notes and technical documentation are available through http://power.ti.com/poe.
Texas Instruments, 1-800-477-8924, www.ti.com