參數(shù)資料
型號(hào)： MAX5971AETI+
廠(chǎng)商： Maxim Integrated
文件頁(yè)數(shù)： 17/22頁(yè)
文件大?。?/td> 2126K
描述： IC CTRLR PD IEEE 802.3AF 28WQFN
產(chǎn)品培訓(xùn)模塊： Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝： 60
類(lèi)型： 以太網(wǎng)供電控制器 PD 開(kāi)關(guān)（PoE）
應(yīng)用： 供電設(shè)備（PSE）
內(nèi)部開(kāi)關(guān)： 是
電流限制： 可調(diào)
電源電壓： 32 V ~ 60 V
工作溫度： -40°C ~ 85°C
安裝類(lèi)型： 表面貼裝
封裝/外殼： 28-WFQFN 裸露焊盤(pán)
供應(yīng)商設(shè)備封裝： 28-TQFN-EP（5x5）
包裝： 管件
______________________________________________________________________________________ 17
Single-Port, 40W, IEEE 802.3af/802.3at PSE
Controller with Integrated MOSFET
Overcurrent Protection
The MAX5971A has an internal sense resistor, R
SENSE
 
(see the Simplified Diagram), connected between the
source of the internal MOSFET and V
EE
 to monitor the
load current. Under normal operating conditions, the
current through R
SENSE
  (I
RSENSE
) never exceeds the
threshold I
LIM
. If I
RSENSE
  exceeds I
LIM
, an internal
current-limiting circuit regulates the gate voltage of the
internal MOSFET, limiting the current. During transient
conditions, if I
RSENSE
 exceeds I
LIM
 by more than 2A, a
fast pulldown circuit activates to quickly recover from the
current overshoot.
In the normal powered state, the MAX5971A checks for
overcurrent conditions, as determined by I
CUT
 = ~88%
of I
LIM
. The t
FAULT
 counter sets the maximum allowed
continuous overcurrent period. This timer is incremented
both in startup and in normal powered state, but under
different conditions. During startup, the counter increas-
es when I
RSENSE
 exceeds I
LIM
, while in the normal pow-
ered state the counter increases when I
RSENSE
 exceeds
I
CUT
. It decreases at a slower pace when I
RSENSE
 
drops below I
LIM
 or I
CUT
. A slower decrement for the
t
FAULT
 counter allows for detection of repeated short-
duration overcurrent events. When the counter reaches
the t
FAULT
 limit, the MAX5971A powers down the port.
For a continuous overstress, a fault occurs exactly after
a period of t
FAULT
.
After a power-off due to an overcurrent fault, the t
FAULT
 
timer is not immediately reset but starts decrementing.
The MAX5971A allows the port to be powered on only
when the t
FAULT
 counter reaches zero. This feature sets
an automatic port power duty-cycle protection to the
internal MOSFET to avoid overheating.
In the normal powered state, the I
LIM
 and I
CUT
 thresh-
olds are set automatically according to the classification
result (see Table 2 for classification results based on
detection current, and the Electrical Characteristics table
for the corresponding thresholds). During startup, I
LIM
is
always set to 420mA regardless of the detected class.
Foldback Current
During startup and normal operation, an internal circuit
senses the port voltage and reduces the current-limit
value and the overcurrent threshold when (V
AGND
  -
V
OUT
) < 27V. The foldback function helps to reduce the
power dissipation on the internal MOSFET. The current
limit eventually reduces down to I
TH_FB
 when (V
AGND
 -
V
OUT
) < 10V (see Figure 3).
Figure 3. Foldback Current Characteristics
V
AGND
- V
OUT
I
LIM
I
TH_FB
10V
27V
I
RSENSE
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MAX5971AETI+T 功能描述:熱插拔功率分布 IEEE 802.3af/at PSE Controller RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube
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MAX5971AEVKIT+ 制造商:Maxim Integrated Products 功能描述:PD INTERFACE CONTROLLER - Boxed Product (Development Kits)
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