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| 型号： | MAX5984AETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 9/22页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR PD IEEE W/MOSFT 28TQFN |
| 标准包装： | 2,500 |
| 系列： | * |
______________________________________________________________________________________ 17
MAX5984
Single-Port, 40W, IEEE 802.3af/802.3at PSE
Controller with Integrated MOSFET
Overcurrent Protection
The MAX5984 has an internal sense resistor, RSENSE
(see the Simplified Diagram), connected between the
source of the internal MOSFET and VEE to monitor the
load current. Under normal operating conditions, the
current through RSENSE (IRSENSE) never exceeds the
threshold ILIM. If IRSENSE exceeds ILIM, an internal
current-limiting circuit regulates the gate voltage of the
internal MOSFET, limiting the current. During transient
conditions, if IRSENSE exceeds ILIM by more than 2A, a
fast pulldown circuit activates to quickly recover from the
current overshoot.
In the normal powered state, the MAX5984 checks for
overcurrent conditions, as determined by ICUT = ~88%
of ILIM. The tFAULT 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 IRSENSE exceeds ILIM, while in the normal pow-
ered state the counter increases when IRSENSE exceeds
ICUT. It decreases at a slower pace when IRSENSE
drops below ILIM or ICUT. A slower decrement for the
tFAULT counter allows for detection of repeated short-
duration overcurrent events. When the counter reaches
the tFAULT limit, the MAX5984 powers down the port. For
a continuous overstress, a fault occurs exactly after a
period of tFAULT.
After a power-off due to an overcurrent fault, the tFAULT
timer is not immediately reset but starts decrementing.
The MAX5984 allows the port to be powered on only
when the tFAULT 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 ILIM and ICUT 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, ILIM 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 (VAGND -
VOUT) < 27V. The foldback function helps to reduce the
power dissipation on the internal MOSFET. The current
limit eventually reduces down to ITH_FB when (VAGND -
VOUT) < 10V (Figure 3).
Figure 3. Foldback Current Characteristics
VAGND - VOUT
ILIM
ITH_FB
10V
27V
IRSENSE
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相关代理商/技术参数 |
参数描述 |
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| MAX5984BETI+ | 制造商:Maxim Integrated Products 功能描述:SINGLE-PORT 40W IEEE 802.3AF/AT PSE CONTROLLER WITH INTEGRAT - Rail/Tube |
| MAX5984CETI+ | 制造商:Maxim Integrated Products 功能描述:SINGLE-PORT 40W IEEE 802.3AF/AT PSE CONTROLLER WITH INTEGRAT - Rail/Tube |
| MAX5984DETI+ | 功能描述:其他电源管理 1-Port 40W IEEE 802.3af/at PSE Ctlr RoHS:否 制造商:Texas Instruments 输出电压范围: 输出电流:4 mA 输入电压范围:3 V to 3.6 V 输入电流: 功率耗散: 工作温度范围:- 40 C to + 110 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-48 封装:Reel |
| MAX5984DETI+T | 功能描述:其他电源管理 1-Port 40W IEEE 802.3af/at PSE Ctlr RoHS:否 制造商:Texas Instruments 输出电压范围: 输出电流:4 mA 输入电压范围:3 V to 3.6 V 输入电流: 功率耗散: 工作温度范围:- 40 C to + 110 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-48 封装:Reel |
| MAX5986AETE+ | 功能描述:直流/直流开关转换器 IEEE802.3 af PD w/ DC/DC Conv RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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