- 您现在的位置：买卖IC网 > PDF目录44997 > LTC4270AIUKG#PBF (LINEAR TECHNOLOGY CORP) SPECIALTY ANALOG CIRCUIT, PQCC52 PDF资料下载
参数资料
| 型号： | LTC4270AIUKG#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PQCC52 |
| 封装： | 8 X 7 MM, LEAD FREE, PLASTIC, QFN-52 |
| 文件页数： | 13/32页 |
| 文件大小： | 344K |
| 代理商： | LTC4270AIUKG#PBF |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页当前第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
LTC4270/LTC4271
20
42701fa
APPLICATIONS INFORMATION
the classification signature current (in this case, Class 3)
in the VCLASS range. Table 5 shows the possible clas-
sification values.
Table 5. 802.3af and 802.3at 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 LTC4270/LTC4271 is in AUTO pin mode, it will ad-
ditionally use the classification result to set the ICUT and
ILIM thresholds. See the Reset and the AUTO/MID Pin
section for more information.
The classification circuitry is disabled when the port is
initially powered up with the AUTO pin low, in shutdown
mode,orwhenthecorrespondingClassEnablebitiscleared.
VOLTAGE (VCLASS)
0
CURRENT
(mA)
60
50
40
30
20
10
0
510
15
20
42701 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
802.3at 2-Event Classification
The 802.3at specification defines two methods of classify-
ing a Type 2 PD. A-grade and B-grade LTC4270/LTC4271
parts support 802.3at 2-event classification.
One method adds extra fields to the Ethernet LLDP data
protocol; although the LTC4270/LTC4271 is compatible
with this classification method, it cannot perform clas-
sification 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 LTC4270/LTC4271 supports
changing the ILIM and ICUT levels on the fly, allowing the
host to complete LLDP classification.
The second 802.3at classification method, known as
2-event classification or ping-pong, is supported by
the LTC4270/LTC4271. A Type 2 PD that is requesting
more than 13W will indicate Class 4 during normal
802.3af classification. If the LTC4270/LTC4271 sees
Class 4, it forces the port to a specified lower voltage
(called the mark voltage, typically 9V), pauses briefly, and
then re-runs classification to verify the Class 4 reading
(Figure 1). It also sets a bit in the High Power Status register
to indicate that it ran the second classification cycle. The
second cycle alerts the PD that it is connected to a Type
2 PSE which can supply Type 2 power levels.
2-event ping-pong classification is enabled by setting a bit
in the port’s High Power Mode register. Note that a ping-
pong enabled port only runs the second classification cycle
when it detects a Class 4 device; if the first cycle returns
Class 0 to 3, the port determines it is connected to a Type 1
PD and does not run the second classification cycle.
Invalid Type 2 Class Combinations
The 802.3at specification defines a Type 2 PD class signa-
ture as two consecutive Class 4 results; a Class 4 followed
by a Class 0-3 is not a valid signature. In AUTO pin mode,
the LTC4270/LTC4271 will power a detected PD regardless
of the classification results, with one exception: if the PD
presents an invalid Type 2 signature (Class 4 followed by
Class 0 to 3), the LTC4270/LTC4271 will not provide power
and will restart the detection process. To aid in diagnosis,
相关PDF资料 |
PDF描述 |
|---|---|
| LTC4274CIUHF#PBF | POWER SUPPLY MANAGEMENT CKT, PQCC38 |
| LTC4274AIUHF-4#TRPBF | POWER SUPPLY MANAGEMENT CKT, PQCC38 |
| LTC4274AIUHF-3#PBF | POWER SUPPLY MANAGEMENT CKT, PQCC38 |
| LTC4274AIUHF-2#TRPBF | POWER SUPPLY MANAGEMENT CKT, PQCC38 |
| LTC4274AIUHF-2#PBF | POWER SUPPLY MANAGEMENT CKT, PQCC38 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4270BIUKG#PBF | 制造商:Linear Technology 功能描述:POE Controller 25.5W 52-Pin QFN EP 制造商:Linear Technology 功能描述:Bulk 制造商:Linear Technology 功能描述:IC POE LTPOE 12-PORT PSE 52-QFN 制造商:Linear Technology 功能描述:IC PSE CONTROLLER 3.3V QFN-52 制造商:Linear Technology 功能描述:PSE CNTRL 12 PORT 25.5W 1M 制造商:Linear Technology 功能描述:IC, PSE CONTROLLER, 3.3V, QFN-52; Input Voltage:3.3V; Supply Current:10mA; UVLO:25V; Digital IC Case Style:QFN; No. of Pins:52; Frequency:1MHz; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:52-QFN ;RoHS Compliant: Yes |
| LTC4270BIUKG#PBF | 制造商:Linear Technology 功能描述:IC, PSE CONTROLLER, 3.3V, QFN-52 |
| LTC4270BIUKG#TRPBF | 制造商:Linear Technology 功能描述:POE Controller 25.5W 52-Pin QFN EP 制造商:Linear Technology 功能描述:PSE CONTROLLER, 12PORT, 57V, QFN-52; Supply Current:10mA; UVLO:25V; Digital IC Case Style:QFN; No. of Pins:52; Duty Cycle (%):6.3%; Frequency:1MHz; Operating Temperature Min:-40C; Operating Temperature Max:85C ;RoHS Compliant: Yes |
| LTC4270CIUKG#PBF | 制造商:Linear Technology 功能描述:POE Controller 13W 52-Pin QFN EP 制造商:Linear Technology 功能描述:IC POE LTPOE 12-PORT PSE 52-QFN 制造商:Linear Technology 功能描述:PSE CNTRL 12 PORT 13W 1MHZ 制造商:Linear Technology 功能描述:IC PSE CONTROLLER 3.3V QFN-52 制造商:Linear Technology 功能描述:IC, PSE CONTROLLER, 3.3V, QFN-52; Input Voltage:3.3V; Supply Current:10mA; UVLO:25V; Digital IC Case Style:QFN; No. of Pins:52; Frequency:1MHz; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:52-QFN ;RoHS Compliant: Yes |
| LTC4270CIUKG#PBF | 制造商:Linear Technology 功能描述:IC PSE CONTROLLER 3.3V QFN-52 制造商:Linear Technology 功能描述:IC, PSE CONTROLLER, 3.3V, QFN-52 |
发布紧急采购，3分钟左右您将得到回复。