National Semiconductor announced a single-chip solution specifically designed for Power over Ethernet (PoE) devices that operate from alternative power sources or the PoE-enabled network. The LM5071 is a Powered Device (PD) interface and DC-DC converter IC that simplifies the design of a variety of PoE applications that require an auxiliary power source such as an AC adapter. Devices powered by a PoE network include IP phones, security cameras and wireless local area network (WLAN) nodes connected through Ethernet networking cables and ports.
Operating these PoE devices from alternate power sources is often necessary to relieve the burden on the Power Sourcing Equipment (PSE) or to operate the device on a network that is not PoE-enabled. The LM5071 integrates a PD front end that accepts power from the PSE or auxiliary power to a single chip with a DC-DC controller that steps down the input voltage to power various PD loads. The device features a maximum input voltage of 80V, user-programmable oscillator frequency up to 1 MHz and over-temperature protection, plus a voltage reference and high-performance error amplifier for non-isolated applications.
Technical Features
<typolist>
Auxiliary power interface: Accepts a wide range of auxiliary power source voltages (12V to 48V) and activates the DC-DC converter to efficiently supply the various loads of the PD.
</typolist>
<typolist>
UVLO threshold and hysteresis: Designers can program the under-voltage lockout (UVLO) trip-point and hysteresis completely independently. This allows control of start-up line currents and the start and stop voltage points as desired in a variety of system applications.
</typolist>
<typolist>
Controls isolated or non-isolated DC-DC converters: Integrates the precision voltage reference and error amplifier for DC-DC feedback in non-isolated converters, including the simple Buck topology. Provides internal pull-up for opto-coupler transistor in isolated designs.
</typolist>
<typolist>
Signature resistor disconnect: The 25 kilohm signature resistor is disconnected after PD detection to reduce power loss. Programmable oscillator frequency: The oscillator for the switching regulator controller is fully programmable, allowing the user to optimize regulator performance.
</typolist>
National’s LM5071 is available in lead-free and standard small-footprint TSSOP-16 packages. The product is priced at $1.45 each in 1,000-unit quantities.
