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參數(shù)資料
| 型號： | LTC4269IDKD-2#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 560 kHz SWITCHING FREQ-MAX, PDSO32 |
| 封裝： | 7 X 4 MM, PLASTIC, M0-229, DFN-32 |
| 文件頁數(shù)： | 6/34頁 |
| 文件大小： | 383K |
| 代理商： | LTC4269IDKD-2#TR |
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LTC4269-2
42692fb
applicaTions inForMaTion
andcurrentwaveformstheLTC4269-2mayencounterwith
the various modes of operation summarized in Table 1.
Table 1. LTC4269-2 Modes of Operation as a Function
of Input Voltage
VPORTP – VPORTN (V) LTC4269-2 MODES OF OPERATION
0V to 1.4V
Inactive (Reset after 1st Classification Event)
1.5V to 9.8V
(5.4V to 9.8V)
25k Signature Resistor Detection Before 1st
Classification Event
(Mark, 11k Signature Corrupt After 1st
Classification Event)
12.5V to On/UVLO
Classification Load Current Active
On/UVLO to 60V
Inrush and Power Applied to PD Load
>71V
Overvoltage Lockout, Classification and Hot Swap
are Disabled.
On/UVLO includes hysteresis. Rising input threshold: 37.2V max.
Falling input threshold: 30.0V min.
These modes satisfy the requirements defined in the
IEEE 802.3af/at specification.
INPUT DIODE BRIDGE
In the IEEE 802.3af/at standard, the modes of operation
reference the input voltage at the PD’s RJ45 connector.
Since the PD must handle power received in either polarity
from either the data or the spare pair, input diode bridges
BR1 and BR2 are connected between the RJ45 connector
and the LTC4269-2 (Figure 2).
The input diode bridge introduces a voltage drop that af-
fectstherangeforeachmodeofoperation.TheLTC4269-2
compensates for these voltage drops so that a PD built
with the LTC4269-2 meets the IEEE 802.3af/at-established
voltage ranges. Note that the Electrical Specifications are
referenced with respect to the LTC4269-2 package pins.
DETECTION
During detection, the PSE looks for a 25k signature resis-
tor which identifies the device as a PD. The PSE will apply
two voltages in the range of 2.8V to 10V and measures
the corresponding currents. Figure 1 shows the detection
voltages V1 and V2 and the corresponding PD current. The
PSE calculates the signature resistance using the
V/I
measurement technique.
The LTC4269-2 presents its precision, temperature-com-
pensated 25k resistor between the VPORTP and VPORTN
pins, alerting the PSE that a PD is present and requests
power to be applied. The LTC4269-2 signature resistor
also compensates for the additional series resistance
introduced by the input diode bridge. Thus a PD built with
the LTC4269-2 conforms to the IEEE 802.3af/at detection
specifications.
SIGNATURE CORRUPT OPTION
In some designs that include an auxiliary power option,
it is necessary to prevent a PD from being detected by a
PSE.TheLTC4269-2signatureresistancecanbecorrupted
with the SHDN pin (Figure 3). Taking the SHDN pin high
will reduce the signature resistor below 11k which is an
invalidsignaturepertheIEEE802.3af/atspecifications,and
alerts the PSE not to apply power. Invoking the SHDN pin
RX–
6
RX+
3
TX–
2
TX+
RJ45
T1
POWERED
DEVICE (PD)
INPUT
42692 F02
1
7
8
5
4
SPARE–
SPARE+
TO PHY
BR2
0.1F
100V
BR1
VPORTP
D3
LTC4269-2
VPORTN
Figure 2. PD Front End Using Diode Bridge on Main and Spare Inputs
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| LTC4269IDKD-2-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:IEEE 802.3at High Power PD and Synchronous Forward Controller with AUX Support |
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| LTC4270AIUKG#PBF | 制造商:Linear Technology 功能描述:POE Controller 90W 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:PSE CNTRL 12 PORT 90W 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 |
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