- 您现在的位置：买卖IC网 > PDF目录262642 > LTC4267CGN-1#TRPBF (LINEAR TECHNOLOGY CORP) Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator; Package: SSOP; No of Pins: 16; Temperature Range: 0°C to +70°C PDF资料下载
参数资料
| 型号： | LTC4267CGN-1#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator; Package: SSOP; No of Pins: 16; Temperature Range: 0°C to +70°C |
| 中文描述： | 1 A SWITCHING CONTROLLER, 240 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-16 |
| 文件页数： | 4/32页 |
| 文件大小： | 925K |
| 代理商： | LTC4267CGN-1#TRPBF |
第1页第2页第3页当前第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
LTC4267-1
12
42671f
Classication
Once the PSE has detected a PD, the PSE may option-
ally classify the PD. Classication provides a method for
more efcient allocation of power by allowing the PSE
to identify lower power PDs and allocate less power for
these devices. The IEEE 802.3af specication denes ve
classes (Table 2) with varying power levels. The designer
selects the appropriate classication based on the power
consumption of the PD. For each class, there is an as-
sociated load current that the PD asserts onto the line
during classication probing. The PSE measures the PD
load current to determine the proper classication and
PD power requirements.
During classication (Figure 4), the PSE presents a xed
voltage between –15.5V and –20.5V to the PD. With the
input voltage in this range, the LTC4267-1 asserts a load
current from the VPORTP pin through the RCLASS resistor.
The magnitude of the load current is set by the RCLASS
resistor. The resistor values associated with each class are
shown in Table 2. Note that the switching regulator will
not interfere with the classication measurement since the
LTC4267-1 has not passed power to the regulator.
Table 2. Summary of IEEE 802.3af Power Classications and
LTC4267-1 RCLASS Resistor Selection
Class
Usage
Maximum
Power Levels
at Input of PD
(W)
Nominal
Classication
Load Current
(mA)
LTC4267-1
RCLASS
Resistor
(
Ω, 1%)
0
Default
0.44 to 12.95
<5
Open
1
Optional
0.44 to 3.84
10.5
124
2
Optional
3.84 to 6.49
18.5
68.1
3
Optional
6.49 to 12.95
28
45.3
4
Reserved
Reserved*
40
30.9
*Class 4 is currently reserved and should not be used.
The IEEE 802.3af specication limits the classication
time to 75ms because a signicant amount of power is
dissipated in the PD. The LTC4267-1 is designed to handle
the power dissipation for this time period. If the PSE prob-
ing exceeds 75ms, the LTC4267-1 may overheat. In this
situation, the thermal protection circuit will engage and
disable the classication current source in order to protect
the part. The LTC4267-1 stays in classication mode until
the input voltage rises above the UVLO turn-on voltage.
VPORTN Undervoltage Lockout
The IEEE specication dictates a maximum turn-on voltage
of 42V and a minimum turn-off voltage of 30V for the PD.
In addition, the PD must maintain large on-off hysteresis to
prevent resistive losses in the wiring between the PSE and
the PD from causing start-up oscillation. The LTC4267-1
incorporates an undervoltage lockout (UVLO) circuit that
monitors the line voltage at VPORTN to determine when
to apply power to the integrated switching regulator
(Figure 5). Before the power is applied to the switching
regulator, the POUT pin is high impedance and sitting at
the ground potential since there is no charge on capacitor
C1. When the input voltage rises above the UVLO turn-on
threshold, the LTC4267-1 removes the detection and clas-
sication loads and turns on the internal power MOSFET.
C1 charges up under the LTC4267-1 current limit control
and the POUT pin transitions from 0V to VPORTN. This
sequence is shown in Figure 1. The LTC4267-1 includes
a hysteretic UVLO circuit on VPORTN that keeps power
applied to the load until the input voltage falls below the
UVLO turn-off threshold. Once the input voltage drops
below –30V, the internal power MOSFET is turned off and
Figure 4. IEEE 802.3af Classication Probing
APPLICATIO S I FOR ATIO
WU
UU
Figure 3. 25k Signature Resistor with Disable
相关PDF资料 |
PDF描述 |
|---|---|
| LTC4267IGN-1#PBF | Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator; Package: SSOP; No of Pins: 16; Temperature Range: -40°C to +85°C |
| LTC4267IGN-1#TRPBF | Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator; Package: SSOP; No of Pins: 16; Temperature Range: -40°C to +85°C |
| LPO3310-102MLB | Power inductor, 20% tol, SMT, RoHS |
| LPO3310-102MLC | Power inductor, 20% tol, SMT, RoHS |
| LPO3310-103MLB | Power inductor, 20% tol, SMT, RoHS |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4267CGN-3#PBF | 功能描述:IC POE 802.3AF W/REG 16-SSOP RoHS:是 类别:集成电路 (IC) >> 接口 - 控制器 系列:- 标准包装:2,450 系列:- 控制器类型:SPI 总线至 I²C 总线桥接 接口:I²C，串行，SPI 电源电压:2.4 V ~ 3.6 V 电流 - 电源:11mA 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-HVQFN（4x4） 包装:托盘 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名称:935286452157SC18IS600IBSSC18IS600IBS-ND |
| LTC4267CGN-3#TRPBF | 功能描述:IC POE 802.3AF INTERFACE 16SSOP RoHS:是 类别:集成电路 (IC) >> 接口 - 控制器 系列:- 标准包装:2,450 系列:- 控制器类型:SPI 总线至 I²C 总线桥接 接口:I²C，串行，SPI 电源电压:2.4 V ~ 3.6 V 电流 - 电源:11mA 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-HVQFN（4x4） 包装:托盘 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名称: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 |
| LTC4267IDHC#PBF | 功能描述:IC POE 802.3AF INTERFACE 16-DFN RoHS:是 类别:集成电路 (IC) >> 接口 - 控制器 系列:- 标准包装:2,450 系列:- 控制器类型:SPI 总线至 I²C 总线桥接 接口:I²C，串行，SPI 电源电压:2.4 V ~ 3.6 V 电流 - 电源:11mA 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-HVQFN（4x4） 包装:托盘 配用:568-3511-ND - DEMO BOARD SPI TO I2C 其它名称:935286452157SC18IS600IBSSC18IS600IBS-ND |
发布紧急采购，3分钟左右您将得到回复。