TPS2370

SLUS537C − AUGUST 2002 − REVISED MARCH 2004

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4

TERMINAL FUNCTIONS

TERMINAL

I/O

DESCRIPTION

NAME

NO.

I/O

DESCRIPTION

CLASS

2

O

Sets classification level with a single resistor to VEE. A precision voltage of 10 V is applied to this pin during

classification. RCLASS values listed in Table 1.

DET

3

O

Connect the 24.9-k

Ω detection resistor (RDET) between this pin and VDD.

EN_DC

6

O

Ties to dc-to-dc converter’s shutdown or soft-start pin. Sinks 80

µA until the load capacitor is fully charged.

ILIM

1

O

Sets start-up current limit level with a resistor to VEE. If using CDC2DCIN > 180 µF, IRUSH must be less than

400 mA. Extra capacitance on ILIM pin can cause oscillations in the current waveform.

RTN

5

O

Return pin. Connect this pin to input return side of the dc-to-dc converter.

VDD

8

I

Connection to PD input port positive voltage.

VEE

4

I

(1) I

25 k

W

R

LIM

(1A)

DETAILED PIN DESCRIPTIONS

ILIM (Pin 1)

Inrush current limiting pin. This pin is used to program the inrush current of the device. By placing a resistor to VEE

from this pin, the inrush current into the load is limited via the following equation:

I

25 k

W

R

LIM

(1A)

CLASS (Pin 2)

Classification pin. The PD can be optionally classified by adding a resistor from this pin to ground. The resistor specific

to each class is given in Table 1: PoE Classification Resistance Values.

DET (Pin3)

this pin to VDD, the user sets the detection resistance. It should be noted that the device itself looks like approximately

1 M

VEE (Pin 4)

Negative supply to the device.

RET (Pin 5)

Negative supply to the load. This pin is the drain side of a FET between the RET pin and the VEE pin, providing hot

swap capabilities to the load. When the FET is switched on, there is approximately 300 m

Ω between this pin and VEE.

EN_DC (Pin 6)

Enable pin for the load. This pin is intended to be used with a dc-to-dc coverter with a soft start capacitor. When power

is not available to the dc-to-dc converter, this pin sinks 80

µA and holds off the soft-start capacitor on the dc-to-dc

converter. Once the voltage across the load is within 1.5 V of its final value, the EN_DC pin stops drawing current

and becomes high impedance, allowing the dc-to-dc converter to soft start normally.

VDD (Pin 8)

Positive supply to the device.

(1)