MAX5972AETE+T【PDF 9/13 页】IC CONTROLLER INTERFACE 16TQFN

收藏本站

您好，
买卖IC网欢迎您。
请登录
免费注册

买卖IC网

Sheet目录43

5页 6页 7页 8页 [9页]10页 11页 12页 13页

IEEE 802.3af/at-Compliant, Powered Device Interface

Controller with Integrated Power MOSFET

_______________________________________________________________________________________ 9

Table 1. Setting Classification Current

is measured across the MAX5972A input V

to V

The PSE determines the class of a PD by applying

a voltage at the PD input and measuring the current

sourced out of the PSE. When the PSE applies a volt-

age between 12.6V and 20V, the MAX5972A exhibits a

current characteristic with a value shown in Table 1. The

PSE uses the classification current information to classify

the power requirement of the PD. The classification cur-

rent includes the current drawn by R

CLS

and the supply

current of the MAX5972A so the total current drawn by

the PD is within the IEEE 802.3af/at standard figures. The

classification current is turned off whenever the device is

in power mode.

2-Event Classification and Detection

During 2-event classification, a Type 2 PSE probes PD

for classification twice. In the first classification event, the

PSE presents an input voltage between 12.6V and 20.5V

and the MAX5972A presents the programmed load

CLASS

. The PSE then drops the probing voltage below

the mark event threshold of 10.1V and the MAX5972A

presents the mark current (I

MARK

). This sequence is

repeated one more time.

When the MAX5972A is powered by a Type 2 PSE, the

2-event identification output 2EC asserts low after the

internal isolation n-channel MOSFET is fully turned on.

2EC current sink is turned off when V

goes below the

UVLO threshold (V

OFF

) and turns on when V

goes

above the UVLO threshold (V

), unless V

goes

below V

THR

to reset the latched output of the Type 2

PSE detection flag.

Alternatively, the 2EC output also serves as a wall

adapter detection output when the MAX5972A is pow-

ered by an external wall power adapter. See the Wall

Power Adapter Detection and Operation section for more

information.

Power Mode (Wake Mode)

The MAX5972A enters power mode when V

rises

above the undervoltage lockout threshold (V

). When

rises above V

, the MAX5972A turns on the inter-

nal n-channel isolation MOSFET to connect V

to RTN

with inrush current limit internally set to 135mA (typ). The

isolation MOSFET is fully turned on when the voltage at

RTN is near V

and the inrush current is reduced below

the inrush limit. Once the isolation MOSFET is fully turned

on, the MAX5972A changes the current limit to 800mA.

The open-drain power-good output (PG) remains low for

a minimum of t

DELAY

until the power MOSFET fully turns

on to keep the downstream DC-DC converter disabled

during inrush.

Undervoltage Lockout

The MAX5972A operates up to a 60V supply voltage with

a turn-on UVLO threshold (V

) at 35.4V and a turn-off

UVLO threshold (V

OFF

) at 31V. When the input voltage is

above V

, the MAX5972A enters power mode and the

internal MOSFET is turned on. When the input voltage

goes below V

OFF

for more than t

OFF_DLY

, the MOSFET

turns off.

Power-Good Output

An open-drain output (PG) is used to allow disabling

downstream DC-DC converter until the n-channel isola-

tion MOSFET is fully turned on. PG is pulled low to V

for a period of t

DELAY

and until the internal isolation

MOSFET is fully turned on. The PG is also pulled low

during sleep mode and coming out of thermal shutdown.

Thermal-Shutdown Protection

The MAX5972A includes thermal protection from exces-

sive heating. If the junction temperature exceeds the

thermal-shutdown threshold of +140NC, the MAX5972A

CLASS

MAXIMUM

POWER USED

BY PD

(W)

CLS

(I)

(V)

CLASS CURRENT SEEN AT

(mA)

IEEE 802.3at PD

CLASSIFICATION CURRENT

SPECIFICATION (mA)

MIN

MAX

MIN

MAX

0.44 to 12.95

615

12.6 to 20

0.44 to 3.94

117

12.6 to 20

3.84 to 6.49

66.5

12.6 to 20

6.49 to 12.95

43.7

12.6 to 20

12.95 to 25.5

30.9

12.6 to 20

> 25.5

21.3

12.6 to 20

发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

*型号	*数量	厂商	批号	封装

添加更多采购

采购需求

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

我的联系方式