Detailed Pin Description

I

(LIM) +

25000

R

(ILIM)

(1)

data sheet

TPS2375

TPS2376

TPS2377

TERMINAL FUNCTIONS

PIN NUMBER

PIN NAME

I/O

DESCRIPTION

TPS2375/77

TPS2376

Connect a resistor from ILIM to VSS to set the start-up inrush current limit.

ILIM

1

1

O

The equation for calculating the resistor is shown in the detailed pin

description section for ILIM.

Connect a resistor from CLASS to VSS to set the classification of the

CLASS

2

2

O

powered device (PD). The IEEE classification levels and corresponding

resistor values are shown in Table 1.

Connect a 24.9-k

Ω detection resistor from DET to VDD for a valid PD

DET

3

3

O

detection.

VSS

4

4

I

Return line on the source side of the TPS2375 from the PSE.

Switched output side return line used as the low-side reference for the

RTN

5

5

O

TPS2375 load.

PG

6

6

O

Open-drain, power-good output; active high.

Used only on the TPS2376. Connect a resistor divider from VDD to VSS to

UVLO

-

7

I

implement the adjustable UVLO feature of the TPS2376.

NC

7

-

No connection

VDD

8

8

I

Positive line from the rectified PSE provided input.

The following descriptions refer to the schematic of Figure 1 and the functional block diagram.

ILIM: A resistor from this pin to VSS sets the inrush current limit per Equation 1:

recommended for compatibility with legacy PSEs.

Inrush current limiting prevents current drawn by the bulk capacitor from causing the line voltage to sag below

the lower UVLO threshold. Adjustable inrush current limiting allows the use of arbitrarily large capacitors and also

accommodates legacy systems that require low inrush currents.

The ILIM pin must not be left open or shorted to VSS.

13 V and 21 V. The classification currents specified in the electrical characteristics table include the bias current

flowing into VDD and any RTN leakage current.

Table 1. CLASSIFICATION

CLASS

PD POWER (W)

802.3af LIMITS (mA)

NOTE

0

0.44 – 12.95

4420 ±1%

0 - 4

Default class

1

0.44 – 3.84

953 ±1%

9 - 12

2

3.84 – 6.49

549 ±1%

17 - 20

3

6.49 – 12.95

357 ±1%

26 - 30

4

-

255 ±1%

36 - 44

Reserved for future use

The CLASS pin must not be shorted to ground.

disconnected when the line voltage exceeds this range to conserve power. This voltage range has been chosen

to allow detection with two silicon rectifiers between the controller and the RJ-45 connector.

VSS: This is the input supply negative rail that serves as a local ground to the TPS2375.

6

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