参数资料
| 型号： | LTC4266IGW#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/30页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR IEEE 802.3AT 36-SSOP |
| 产品培训模块： | Power over Ethernet |
| 标准包装： | 32 |
| 控制器类型： | 以太网控制器（IEEE 802.3） |
| 接口： | I²C，2 线串口 |
| 电源电压： | 3.3V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-BSOP（0.295"，7.50mm 宽） |
| 供应商设备封装： | 36-SSOP |
| 包装： | 管件 |
| 产品目录页面： | 1338 (CN2011-ZH PDF) |
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LTC4266
18
4266fd
APPLICATIONS INFORMATION
The signature detection circuitry is disabled when the port
is initially powered up with the AUTO pin low, in shutdown
mode, or when the corresponding detect enable bit is
cleared.
Detection of Legacy PDs
Proprietary PDs that predate the original IEEE 802.3af
standard are commonly referred to today as legacy de-
vices. One type of legacy PD uses a large common mode
capacitance (>10μF) as the detection signature. Note that
PDs in this range of capacitance are defined as invalid, so
a PSE that detects legacy PDs is technically noncompliant
with the IEEE spec.
The LTC4266 can be configured to detect this type of legacy
PD. Legacy detection is disabled by default, but can be
manually enabled on a per-port basis. When enabled, the
port will report detect good when it sees either a valid IEEE
PD or a high-capacitance legacy PD. With legacy mode
disabled, only valid IEEE PDs will be recognized.
CLASSIFICATION
802.3af Classification
A PD can optionally present a classification signature to
the PSE to indicate the maximum power it will draw while
operating. The IEEE specification defines this signature
as a constant current draw when the PSE port voltage
is in the VCLASS range (between 15.5V and 20.5V), with
the current level indicating one of 5 possible PD classes.
Figure 13 shows a typical PD load line, starting with the
slope of the 25kΩ signature resistor below 10V, then
transitioning to the classification signature current (in
this case, Class3) in the VCLASS range. Table 4 shows the
possible classification values.
Table 4. Classification Values
CLASS
RESULT
Class 0
No Class Signature Present; Treat Like Class 3
Class 1
3W
Class 2
7W
Class 3
13W
Class 4
25.5W (Type 2)
If classification is enabled, the port will classify the PD
immediately after a successful detection cycle in semi-auto
or AUTO pin modes, or when commanded to in manual
mode. It measures the PD classification signature by ap-
plying 18V for 12ms (both values typical) to the port via
the OUTn pin and measuring the resulting current; it then
reports the discovered class in the port status register. If
the LTC4266 is in AUTO pin mode, it will additionally use
the classification result to set the ICUT and ILIM thresholds.
See the Reset and the AUTO/MID Pins section for more
information.
The classification circuitry is disabled when the port is
initially powered up with the AUTO pin low, in shutdown
mode, or when the corresponding class enable bit is
cleared.
802.3at 2-Event Classification
The 802.3at spec defines two methods of classifying a
Type 2 PD.
One method adds extra fields to the Ethernet LLDP data
protocol; although the LTC4266 is compatible with this
classification method, it cannot perform classification
directly since it doesn’t have access to the data path.
LLDP classification requires the PSE to power the PD as
a standard 802.3af (Type 1) device. It then waits for the
host to perform LLDP communication with the PD and
update the PSE port data. The LTC4266 supports chang-
ing the ILIM and ICUT levels on the fly, allowing the host
to complete LLDP classification.
VOLTAGE (VCLASS)
0
CURRENT
(mA)
60
50
40
30
20
10
0
510
15
20
4266 F13
25
TYPICAL
CLASS 3
PD LOAD
LINE
48mA
33mA
PSE LOAD LINE
23mA
14.5mA
6.5mA
CLASS 4
CLASS 2
CLASS 1
CLASS 0
CLASS 3
OVER
CURRENT
Figure 13. PD Classification
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4266IUHF#PBF | 制造商:Linear Technology 功能描述:POE Controller 25.5W 38-Pin QFN EP 制造商:Linear Technology 功能描述:IC POE 802.3AT QUAD PSE 38-QFN 制造商:Linear Technology 功能描述:POE CNTRL QUAD 25.5W 1MHZ 制造商:Linear Technology 功能描述:IC, POE CONTROLLER, 3.3V, QFN-38; Input Voltage:3.3V; Supply Current:-2.4mA; UVLO:25V; Digital IC Case Style:QFN; No. of Pins:38; Frequency:1MHz; Operating Temperature Min:-40C; Operating Temperature Max:85C; MSL:MSL 1 - Unlimited ;RoHS Compliant: Yes |
| LTC4266IUHF#TRPBF | 制造商:Linear Technology 功能描述:POE Controller 25.5W 38-Pin QFN EP |
| LTC4267 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4267-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator |
| LTC4267-3 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator |
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