- 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： | 11/32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页当前第11页第12页第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
19
42701fa
APPLICATIONS INFORMATION
FIRST
DETECTION
POINT
SECOND
DETECTION
POINT
VALID PD
25kΩ SLOPE
275
165
CURRENT
(μA)
0V-2V
OFFSET
VOLTAGE
42701 F12
Figure 12. PD Detection
Table 4. Detection Status
MEASURED PD SIGNATURE
DETECTION RESULT
Incomplete or Not Yet Tested
Detect Status Unknown
< 2.4k
Short Circuit
Capacitance > 2.7μF
CPD too High
2.4k < RPD < 17k
RSIG too Low
17k < RPD < 29k
Detect Good
> 29k
RSIG too High
> 50k
Open Circuit
Voltage > 10V
Port Voltage Outside Detect Range
More on Operating Modes
The port’s operating mode determines when the LTC4270/
LTC4271 runs a detection cycle. In manual mode, the port
will idle until the host orders a detect cycle. It will then
run detection, report the results, and return to idle to wait
for another command.
In semi-auto mode, the LTC4270/LTC4271 autonomously
polls a port for PDs, but it will not apply power until com-
manded to do so by the host. The Port Status register is
updated at the end of each detection cycle.
If a valid signature resistance is detected and classification
is enabled, the port will classify the PD and report that
result as well. The port will then wait for at least 100ms (or
2 seconds if midspan mode is enabled), and will repeat the
detection cycle to ensure that the data in the Port Status
register is up-to-date.
If the port is in semi-auto mode and high power opera-
tion is enabled, the port will not turn on in response to
a power-on command unless the current detect result is
detect good. Any other detect result will generate a tSTART
fault if a power-on command is received. In high power
mode the port must be placed in manual mode to force a
port on regardless of detect outcome.
Behavior in AUTO pin mode is similar to semi-auto; however,
after detect good is reported and the port is classified (if
classification is enabled), it is automatically powered on
without further intervention. In standalone (AUTO pin)
mode, the ICUT and ILIM thresholds are automatically set;
see the Reset and the AUTO/MID Pins section for more
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 stan-
dard are commonly referred to today as legacy devices. 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 LTC4270/LTC4271 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 may 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 25k signature resistor below 10V, then transitioning to
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。