FEATURES

Integrated Power Interface Switch for IEEE

802.3af Powered Devices (PDs)

Precision UVLO Thresholds

20-ms UVLO Off-Time Delay

Provides PD Detection Signature

Provides PD Classification Signature

(Class 0−4)

Programmable Inrush Current Limit

Internal 0.3-Ω Low-Side FET

Interfaces to DC/DC Soft-Start for DC/DC

Enable

Internal Thermal Protection – Disconnects

PD Load

8-Pin SOIC, 8-Pin TSSOP Packages

APPLICATIONS

VoIP Phones

Internet Appliances

Wireless LAN Access Points

Bluetooth Access Points

DESCRIPTION

Acting as an interface between the Power Source

Equipment (PSE) and the Powered Device (PD),

the TPS2371 performs all detection, class−

ification, inrush current limiting, and switch FET

control that is necessary for compatibility with

Legacy/IEEE 802.3af Standard. The TPS2371

incorporates precision UVLO thresholds and

hysteresis as well as a UVLO off-time delay to

enable Legacy IEEE802.3af PoE compatibilty. An

internal 0.3-Ω FET provides maximum power

delivery. As an additional feature, the TPS2371

interfaces with the enable/soft-start signal of a

dc-to-dc converter, eliminating the need to have

an accurate UVLO in the dc-to-dc converter.

At low input voltages (1.8 V to 10 V), the TPS2371

draws less than 12 μA, allowing accurate sensing

of the external 24.9-kΩ discovery resistor. At input

voltages between 15 V and 20 V, an external

resistor sets the level of current to be drawn during

classification mode. TPS2371 is compatible with

current as well as voltage measurement schemes

for classification. Above 20-V input, the

classification current is shut off, reducing internal

power dissipation.