MAX5922AEUI+【PDF 18/21 页】IC NETWORK PWR SW +48V 28-TSSOP

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

14页 15页 16页 17页 [18页]19页 20页 21页

+48V, Single-Port Network Power Switch

For Power-Over-LAN

18 ______________________________________________________________________________________

This overcurrent timeout enables the MAX5922 to operate

in a periodic overcurrent condition without causing a fault

(see Figure 9).

Power-OK (POK)

POK goes open-drain t

POK_HIGH

(88ms) after V

OUT

rises to within V

THPOK

(0.75V) from V

. POK goes low

POK_LOW

(1.4ms) after V

OUT

drops 0.82V below V

Zero-Current Detection

Zero-current detection is enabled if ZC_EN is high and

only after the startup period has finished (indicated by

POK going high). When V

SENSE

falls below the zero-

current threshold (V

ZCTH

) for a continuous t

ZCDEL

350ms, a zero-current fault is generated. The MOSFET

is turned off and ZC is latched low. The MAX5922A and

the MAX5922B/MAX5922C (with DET_DIS = low) imme-

diately begin a PD detection sequence, regardless of

the status of the LATCH input. ZC is unlatched and

goes high impedance after a PD is detected. ZC is also

high impedance during initial power-up. When

DET_DIS is high (MAX5922B/MAX5922C), a zero-cur-

rent fault shuts down the MOSFET and the EN pin

needs to be toggled to unlatch the fault.

At any time during a zero-current condition, if V

SENSE

goes above V

ZCTH

for the zero-current deglitch time

ZC_DEG

= 10ms), the zero-current counter resets to

zero and a zero-current fault is not generated. Bring

ZC_EN low to disable the zero-current detection func-

tion. ZC stays high impedance in this mode.

Thermal Shutdown

If the MAX5922 die temperature reaches +150癈, an

overtemperature fault is generated. The MOSFET turns

off and FAULT goes low. The MAX5922 die tempera-

ture must cool down below 120癈 before the overtem-

perature fault condition is removed (see Fault

Management section).

Fault Report (FAULT)

FAULT goes low when there is an overcurrent fault and/or

an overtemperature fault. FAULT is open-drain otherwise.

After a fault, the FAULT signal is latched low. FAULT is

unlatched at the beginning of the next power mode.

Fault Management

The MAX5922 offers either latched-off or auto-retry fault

management configurable by the LATCH input.

Bringing LATCH high puts the device into latch mode

while pulling LATCH low selects the autoretry option.

In latch mode, the MAX5922 turns the MOSFET off and

keeps it off after an overcurrent fault or an over-temper-

ature fault. After the fault condition goes away, recycle

the power supplies or toggle the EN pin low and high

again to unlatch the part. However, the part waits a

RESTART

period (1.92s) before recovering from a fault

condition and resuming normal operation.

In autoretry mode, the MAX5922 turns the MOSFET off

after an overcurrent or overtemperature fault. After the

fault condition is removed, the device waits a t

RESTART

period (1.92s) and then automatically restarts and

enters the PD detection mode (MAX5922A and

MAX5922B/MAX5922C with DET_DIS low). If DET_DIS

is high (MAX5922B/MAX5922C), the MAX5922B/

MAX5922C automatically restart into the power-up

mode after t

RESTDRT

. If the fault was due to an

overtemperature condition, the MAX5922 waits for its

die temperature to cool down below the hysteresis level

before starting the t

RESTART

time.

Detection Collision Avoidance

Detection collision avoidance is enabled by connecting

the DCA pin directly to V

DIG

and disabled by connect-

ing it to DGND. When DCA is high, the MAX5922A acti-

vates a back-off time, t

DCA

(2.8s), after every failed

detection during PD detection mode. During this back-

off time, the MAX5922A turns off the MOSFET and dri-

ves the OUT pin to high impedance. This function is

required by the IEEE 802.3af standard if the PSE

resides in a midspan system. After t

DCA

, the

MAX5922A starts a PD detection sequence. The

MAX5922B has this function internally disabled and the

MAX5922C has this function internally enabled.

RESTART

FAULT

OUT

LIMIT

Figure 9. Overcurrent Response

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