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參數(shù)資料
| 型號： | LTC4259AIGW-1#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 電源管理 |
| 英文描述： | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: -40°C to +85°C |
| 中文描述： | 4-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO36 |
| 封裝： | 0.300 INCH, LEAD FREE, PLASTIC, SSOP-36 |
| 文件頁數(shù)： | 21/32頁 |
| 文件大小： | 416K |
| 代理商： | LTC4259AIGW-1#TRPBF |
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LTC4259A-1
28
4259a1fa
LOGIC LEVEL SUPPLY
In additon to the 48V used to source power to each port,
a logic level supply is required to power the digital portion
of the LTC4259A-1. To simplify design and meet voltage
isolation requirements, the logic level supply can be
generated from the isolated – 48V supply. Figure 21
shows an example method using an LT
1619 to control
a –48V to 3.3V current mode supply. This boost con-
verter topology uses the LT1619 current mode controller
and a current mirror which reflects the 3.3V output
voltage to the –48V rail, improving the regulation toler-
ance over the more traditional large resistor voltage
divider. This approach achieves high accuracy with a
transformerless design.
IEEE 802.3af COMPLIANCE AND EXTERNAL
COMPONENT SELECTION
The LTC4259A-1 is designed to control power delivery in
IEEE 802.3af compliant Power Sourcing Equipment (PSE).
Because proper operation of the LTC4259A-1 may depend
on external signals and power sources, like the –48V
supply (VEE) or the OSCIN oscillator source, external
components such as the sense resistors (RS), and possi-
bly software running on an external microprocessor,
using the LTC4259A-1 in a PSE does not guarantee
802.3af compliance. Using an LTC4259A-1 does get you
most of the way there. This section discusses the rest of
the elements that go along with the LTC4259A-1 to make
an 802.3af compliant PSE. Each paragraph below ad-
dresses a component which is critical for PSE compliance
as well as possible pitfalls that can cause a PSE to be
noncompliant. For further assistance please contact Lin-
ear Technology’s Applications department.
Sense Resistors
The LTC4259A-1 is designed to use a 0.5
sense resistor,
RS, to monitor the current through each port. The value of
the sense resistor has been minimized in order to reduce
power loss and as a consequence, the voltage which the
LTC4259A-1 must measure is small. Each port may be
drawing up to 450mA with this current flowing through the
sense resistor and associated circuit board traces. To
prevent parasitic resistance on the circuit board from
obscuring the voltage drop across the sense resistor, the
LTC4259A-1 must Kelvin sense the resistor voltage. One
way to achieve Kelvin sensing is “star grounding,” shown
pictorially in Figure 1. Another option is to use a – 48V
power plane to connect the sense resistor and the
LTC4259A-1 VEE pin. Either of these strategies will prevent
voltages developed across parasitic circuit board resis-
tances from affecting the LTC4259A-1 current measure-
ment accuracy. The precision of the sense resistor directly
affects the measurement of the IEEE parameters IINRUSH,
APPLICATIO S I FOR ATIO
WU
UU
DRV
100
100
H
4.7
H
B1100
10
F
16V
4700pF
100pF
CMPZ4702B
ISOLATED
GND
ISOLATED
–48V
Si2328DS
FMMT593
87
6
5
2
3
4
1
GATE
VIN
VC
S/S
SENSE
LT1619
FB
GND
Si2328DS
510
47k
3.32k
1%
0.100
1%
1W
1.24k
1%
100k
4259A F21
910k
1
F
100V
+
VEE
10
47
F
10V
VDD
3.3V
300mA
+
47
F
10V
ISOLATED
GND
+
Figure 21. –48V to 3.3V Boost Converter
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC4259CGW-ES | 制造商:LINEAR_TECH 功能描述: |
| LTC4260 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:UV, OV and Reverse Supply Protection Controller Low Operating Current: 125μA |
| LTC4260CGN | 制造商:Linear Technology 功能描述:Hot Swap Controller 1-CH 80V 24-Pin SSOP N |
| LTC4260CGN#PBF | 功能描述:IC CTLR HOT SWAP I2C 24-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:119 系列:- 類型:熱交換控制器 應(yīng)用:通用型，PCI Express? 內(nèi)部開關(guān):無 電流限制:- 電源電壓:3.3V，12V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:80-TQFP 供應(yīng)商設(shè)備封裝:80-TQFP（12x12） 包裝:托盤 產(chǎn)品目錄頁面:1423 (CN2011-ZH PDF) |
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