STHS4257L datasheet(7/18 Pages) STMICROELECTRONICS

7 / 18 page

Obsolete

Product(s)

- Obsolete

Product(s)

STHS4257A, STHS4257A1, STHS4257L, STHS4257L1

Summary description

7/18

1.1

Pin descriptions

1.1.1

Classification (RCLASS)

This is the Classification pin. Connect a Classification resistor between this pin and VIN to

tell the PSE which power class will be connected. Leave it open for Class 0.

Note: Do not connect this pin directly to VIN. For power classes and RCLASS resistor values,

see Table 3.

1.1.2

VIN

This is negative return power line to PSE.

1.1.3

Power supply (GND)

This is the Power Input/Output, positive rail.

1.1.4

Signature disable input (SIGDISA)

This pin is internally pulled down to VIN to present a valid signature to PSE. Connect to VIN

if it is unused. Tie to GND to present an invalid signature.

Note: This signal is available for STHS4257A1 and STHS4257L1 only.

1.1.5

Power Good output (PWRGD)

This pin indicates that the STHS4257x/x1 power MOSFET is fully on and works in normal

operation mode (Power Good). Open drain, low impedance means that the power is good; in

all other cases, the impedance is high (referenced to VIN).

1.1.6

Negative power output (VOUT)

This is the Power Output, negative rail.

1.2

IEEE802.3af PD power classes

Table 3.

IEEE802.3af PD power classes and corresponding RCLASS values

Class 4 is currently reserved and should not be used.

Class

Usage

Max. power levels

at input of PD (W)

Nominal classification

load current (mA)

RCLASS Resistor

(

Ω, 1%)

Default

0.44 to 12.95

< 5

Open

Optional

0.44 to 3.84

10.5

124

Optional

3.84 to 6.49

18.5

68.1

Optional

6.49 to 12.95

45.3

Reserved

Reserved (1)

30.9

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