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.