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參數(shù)資料
| 型號： | LTC4267CGN-1#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 240 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SSOP-16 |
| 文件頁數(shù)： | 9/32頁 |
| 文件大小： | 925K |
| 代理商： | LTC4267CGN-1#TR |
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LTC4267-1
17
42671f
Diode Bridge
IEEE 802.3af allows power wiring in either of two congu-
rations: on the TX/RX wires or via the spare wire pairs in
the RJ45 connector. The PD is required to accept power in
either polarity on either the main or spare inputs; therefore
it is common to install diode bridges on both inputs in
order to accommodate the different wiring congurations.
Figure 9 demonstrates an implementation of these diode
bridges. The IEEE 802.3af specication also mandates
that the leakage back through the unused bridge be less
than 28μA when the PD is powered with 57V.
The IEEE standard includes an AC impedance requirement
in order to implement the AC disconnect function. Capaci-
tor C14 in Figure 9 is used to meet this AC impedance
requirement. A 0.1μF capacitor is recommended for this
application.
The LTC4267-1 has several different modes of opera-
tion based on the voltage present between VPORTN and
VPORTP pins. The forward voltage drop of the input diodes
in a PD design subtracts from the input voltage and will
affect the transition point between modes. When using
the LTC4267-1, it is necessary to pay close attention to
this forward voltage drop. Selection of oversized diodes
will help keep the PD thresholds from exceeding IEEE
specications.
The input diode bridge of a PD can consume over 4%
of the available power in some applications. It may be
desirable to use Schottky diodes in order to reduce power
loss. However, if the standard diode bridge is replaced
with a Schottky bridge, the transition points between the
modes will be affected. Figure 10 shows a technique for
using Schottky diodes while maintaining proper threshold
points to meet IEEE 802.3af compliance. D13 is added to
compensate for the change in UVLO turn-on voltage caused
by the Schottky diodes and consumes little power.
Classication Resistor Selection (RCLASS)
The IEEE specication allows classifying PDs into four
distinct classes with class 4 being reserved for future use
(Table 2). An external resistor connected from RCLASS to
VPORTN (Figure 4) sets the value of the load current. The
APPLICATIO S I FOR ATIO
WU
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Figure 9. PD Front End with Isolation Transformer, Diode Bridges and Capacitor
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC4267CGN-1-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator |
| LTC4267CGN-3#PBF | 功能描述:IC POE 802.3AF W/REG 16-SSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標(biāo)準(zhǔn)包裝:2,450 系列:- 控制器類型:SPI 總線至 I²C 總線橋接 接口:I²C，串行，SPI 電源電壓:2.4 V ~ 3.6 V 電流 - 電源:11mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND |
| LTC4267CGN-3#TRPBF | 功能描述:IC POE 802.3AF INTERFACE 16SSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標(biāo)準(zhǔn)包裝:2,450 系列:- 控制器類型:SPI 總線至 I²C 總線橋接 接口:I²C，串行，SPI 電源電壓:2.4 V ~ 3.6 V 電流 - 電源:11mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND |
| LTC4267CGNPBF | 制造商:Linear Technology 功能描述:Hot Swap Controller 1-Ch -57V SSOP16 |
| LTC4267IDHC | 制造商:Linear Technology 功能描述:Hot Swap Controller 1-CH -57V 16-Pin DFN EP |
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