- 您現在的位置：買賣IC網 > PDF目錄179919 > LTC4257IS8#TRPBF (LINEAR TECHNOLOGY CORP) IEEE 802.3af PD Power over Ethernet Interface Controller; Package: SO; No of Pins: 8; Temperature Range: -40°C to +85°C PDF資料下載
參數資料
| 型號： | LTC4257IS8#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 網絡接口 |
| 英文描述： | IEEE 802.3af PD Power over Ethernet Interface Controller; Package: SO; No of Pins: 8; Temperature Range: -40°C to +85°C |
| 中文描述： | DATACOM, NETWORK INTERFACE SUPPORT CIRCUIT, PDSO8 |
| 封裝： | 0.150 INCH, LEAD FREE, PLASTIC, SOP-8 |
| 文件頁數： | 7/20頁 |
| 文件大?。?/td> | 258K |
| 代理商： | LTC4257IS8#TRPBF |
LTC4257
15
4257fb
Classification Resistor Selection (RCLASS)
IEEE 802.3af allows classifying PDs into four distinct
classes with class 4 being reserved for future use (Table 2).
An external resistor connected from RCLASS to VIN (Fig-
ure 3) sets the value of the classification current. The
designer should determine which power category the PD
falls into and then select the appropriate value of RCLASS
from Table 2. If a unique classification current is required,
the value of RCLASS can be calculated as:
RCLASS = 1.237V/(IDESIRED – IIN_CLASS)
where IIN_CLASS is the LTC4257 IC supply current during
classification and is given in the electrical specifications.
The RCLASS resistor must be 1% or better to avoid
degrading the overall accuracy of the classification cir-
cuit. Resistor power dissipation will be 50mW maximum
and is transient so heating is typically not a concern. In
order to maintain loop stability, the layout should
minimize capacitance at the RCLASS node. The classifica-
tion circuit can be disabled by floating the RCLASS pin. The
RCLASS pin should not be shorted to VIN as this would
force the LTC4257 classification circuit to attempt to
source very large currents. In this case, the LTC4257 will
quickly go into thermal shutdown.
Power Good Interface
The PWRGD signal is controlled by a high voltage, open-
drain transistor. Examples of active-high and active-low
interface circuits for controlling the PD load are shown in
Figure 10.
In some applications it is desirable to ignore intermittent
power bad conditions. This can be accomplished by
including capacitor C15 in Figure 10 to form a lowpass
filter. With the components shown, power bad conditions
less than about 200
s will be ignored. Conversely, in other
applications it may be desirable to delay assertion of
PWRGD to the PD load. The PWRGD signal can be delayed
with the addition of capacitor C17 in Figure 10.
APPLICATIO S I FOR ATIO
WU
UU
Figure 10. Power Good Interface Examples
GND
C1
5
F
100V
VIN
8
4
–48V
VOUT 5
*C15 OPTIONAL TO FILTER PWRGD.
SEE APPLICATIONS INFORMATION
LTC4257
PD
LOAD
SHDN
PWRGD
6
D6
5.1V
MMBZ5231B
C15*
0.047
F
10V
R9
100k
R9
100k
R18
10k
R18
10k
+
GND
C1
5
F
100V
Q1
FMMT2222
D6
MMBD4148
VIN
8
4
–48V
VOUT 5
LTC4257
4257 F10
PD
LOAD
RUN
C17*
PWRGD
6
INTERNAL
PULLUP
+
ACTIVE-LOW ENABLE, 5.1V SWING
ACTIVE-HIGH ENABLE FOR RUN PIN WITH INTERNAL PULLUP
TO
PSE
TO
PSE
C15*
0.047
F
10V
*C15 AND C17 OPTIONAL TO FILTER PWRGD.
SEE APPLICATIONS INFORMATION
相關PDF資料 |
PDF描述 |
|---|---|
| LTC4259ACGW-1#PBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
| LTC4259ACGW-1#TRPBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
| LTC4259AIGW-1#PBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: -40°C to +85°C |
| LTC4259AIGW-1#TRPBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: -40°C to +85°C |
| LTC4259ACGW#PBF | Quad IEEE 802.3af Power over Ethernet Controller with AC Disconnect; Package: SSOP; No of Pins: 36; Temperature Range: 0°C to +70°C |
相關代理商/技術參數 |
參數描述 |
|---|---|
| LTC4258 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4258_09 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Quad IEEE 802.3af Power over Ethernet Controller with Integrated Detection |
| LTC4258CGW | 制造商:Linear Technology 功能描述:POWER OVER ETHERNET CONTROLLER |
| LTC4258CGW#PBF | 功能描述:IC POE 802.3AF QUAD 36-SSOP RoHS:是 類別:集成電路 (IC) >> 接口 - 控制器 系列:- 標準包裝: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 供應商設備封裝:24-HVQFN（4x4） 包裝:托盤 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名稱:935286452157SC18IS600IBSSC18IS600IBS-ND |
| LTC4258CGW#TR | 制造商:Linear Technology 功能描述:POWER OVER ETHERNET CONTROLLER |
發(fā)布緊急采購，3分鐘左右您將得到回復。