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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)： | 10/34頁 |
| 文件大?。?/td> | 383K |
| 代理商： | LTC4269IDKD-2#TR |
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LTC4269-2
42692fb
THERMAL PROTECTION
TheIEEE802.3af/atspecificationrequiresaPDtowithstand
any applied voltage from 0V to 57V indefinitely. However,
there are several possible scenarios where a PD may
encounter excessive heating.
During classification, excessive heating may occur if the
PSEexceedsthe75msprobingtimelimit.Atturn-on,when
the load capacitor begins to charge, the instantaneous
power dissipated by the PD interface can be large before
it reaches the line voltage. And if the PD experiences a
fast input positive voltage step in its operational mode
(for example, from 37V to 57V), the instantaneous power
dissipated by the PD Interface can be large.
TheLTC4269-2includesathermalprotectionfeaturewhich
protects the LTC4269-2 from excessive heating. If the
LTC4269-2junctiontemperatureexceedstheovertempera-
turethreshold,theLTC4269-2discontinuesPDoperations.
Normal operation resumes when the junction temperature
falls below the overtemperature threshold and when C1 is
charged up and power good becomes inactive.
EXTERNAL INTERFACE AND COMPONENT SELECTION
Transformer
Nodes on an Ethernet network commonly interface to the
outside world via an isolation transformer. For PDs, the
isolation transformer must also include a center tap on
the RJ45 connector side (see Figure 7).
The increased current levels in a Type 2 PD over a Type 1
increase the current imbalance in the magnetics which
can interfere with data transmission. In addition, proper
termination is also required around the transformer to
provide correct impedance matching and to avoid radiated
and conducted emissions. Transformer vendors such as
Bel Fuse, Coilcraft, Halo, Pulse and Tyco (Table 4) can
assist in selecting an appropriate isolation transformer
and proper termination methods.
Table 4. Power over Ethernet Transformer Vendors
VENDOR
CONTACT INFORMATION
Bel Fuse Inc.
206 Van Vorst Street
Jersey City, NJ 07302
Tel: 201-432-0463
www.belfuse.com
Coilcraft Inc.
1102 Silver Lake Road
Gary, IL 60013
Tel: 847-639-6400
www.coilcraft.com
Halo Electronics
1861 Landings Drive
Mountain View, CA 94043
Tel: 650-903-3800
www.haloelectronics.com
PCA Electronics
16799 Schoenborn Street
North Hills, CA 91343
Tel: 818-892-0761
www.pca.com
Pulse Engineering
12220 World Trade Drive
San Diego, CA 92128
Tel: 858-674-8100
www.pulseeng.com
Tyco Electronics
308 Constitution Drive
Menlo Park, CA 94025-1164
Tel: 800-227-7040
www.circuitprotection.com
Input Diode Bridge
Figure 2 shows how two diode bridges are typically con-
nected in a PD application. One bridge is dedicated to the
data pair while the other bridge is dedicated to the spare
pair. The LTC4269-2 supports the use of either silicon or
Schottkyinputdiodebridges.However,therearetrade-offs
in the choice of diode bridges.
An input diode bridge must be rated above the maximum
current the PD application will encounter at the tempera-
ture the PD will operate. Diode bridge vendors typically
call out the operating current at room temperature, but
derate the maximum current with increasing temperature.
Consult the diode bridge vendors for the operating current
de-rating curve.
14
13
12
1
2
3
RX–
6
RX+
3
TX–
2
TX+
RJ45
T1
COILCRAFT ETH1-230LD
42692 F07
1
7
8
5
4
10
9
11
5
6
4
D3
SMAJ58A
TVS
BR1
HD01
BR2
HD01
TO PHY
VPORTP
LTC4269-2
C1
VPORTN VNEG
SPARE–
SPARE+
C14
0.1F
100V
Figure 7. PD Front End with Isolation Transformer, Diode
Bridges, Capacitors and a Transient Voltage Suppressor (TVS)
applicaTions inForMaTion
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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 |
| LTC4270 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:12-Port PoE/PoE+/LTPoE++ PSE Controller |
| LTC4270/ | 制造商:LINER 制造商全稱:Linear Technology 功能描述:8-Port PoE/PoE PSE Controller |
| LTC4270_12 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:12-Port PoE/PoE+/LTPoE++ PSE Controller |
| 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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