TPS2371

SLUS566A − JULY 2003 − REVISED NOVEMBER 2003

LEGACY/IEEE802.3af COMPATIBLE POWER INTERFACE SWITCH

FOR POWER OVER ETHERNET (PoE) POWERED DEVICES

1

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FEATURES

802.3af Powered Devices (PDs)

(Class 0−4)

Enable

PD Load

APPLICATIONS

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-k

Ω 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.

3

1

2

4

5

TPS2371

6

DC/DC

Converter/

Controller

8

Ethernet

Appliance

VREG

44 V

TO

57 V

V+

V−

7

SIMPLIFIED APPLICATION DIAGRAM

RDET

RLIM

CSS

CDCDCIN

RCLASS

CBYPASS

CDEL

UDG−03092

5 V

CLIM

SMAJ54A

Bluetooth is a trademark of the Bluetooth SIG, Inc.

Copyright

 1999 − 2003, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.