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| 型号： | LTC4267IGN-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: -40°C to +85°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： | 6/32页 |
| 文件大小： | 925K |
| 代理商： | LTC4267IGN-1#TRPBF |
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LTC4267-1
14
42671f
the LTC4267-1 will attempt to quickly charge capacitor C1
using an internal secondary current limit circuit. In this
scenario, the PSE current limit should provide the overall
limit for the circuit. For slower rising inputs, the 375mA
current limit in the LTC4267-1 will set the charge rate of
the capacitor C1. In either case, the
PWRGD signal may
go inactive briey while the capacitor is charged up to the
new line voltage. In the design of a PD, it is necessary
to determine if a step in the input voltage will cause the
PWRGD signal to go inactive and how to respond to this
event. In some designs, it may be desirable to lter the
PWRGD signal so that intermittent power bad conditions
are ignored. Figure 7 demonstrates a method to insert a
lowpass lter on the power good interface.
For PD designs that use a large load capacitor and also con-
sume a lot of power, it is important to delay activation of the
switching regulator with the
PWRGD signal. If the regulator
is not disabled during the current-limited turn-on sequence,
the PD circuitry will rob current intended for charging up
the load capacitor and create a slow rising input, possibly
causing the LTC4267-1 to go into thermal shutdown.
The
PWRGD pin connects to an internal open drain, 100V
transistor capable of sinking 1mA. Low impedance to
VPORTN indicates power is good. PWRGD is high imped-
ance during signature and classication probing and in
the event of a thermal overload. During turn-off,
PWRGD
is deactivated when the input voltage drops below 30V.
In addition,
PWRGD may go active briey at turn-on for
fast rising input waveforms.
PWRGD is referenced to the
VPORTN pin and when active, will be near the VPORTN po-
tential. Connect the
PWRGD pin to the switching regulator
circuitry as shown in Figure 7.
Figure 6. LTC4267-1 Power Good
APPLICATIO S I FOR ATIO
WU
UU
Figure 7. Power Good Interface Examples
PD Interface Thermal Protection
The LTC4267-1 PD Interface includes thermal overload
protection in order to provide full device functionality
in a miniature package while maintaining safe operating
temperatures. Several factors create the possibility of
signicant power dissipation within the LTC4267-1. At
turn-on, before the load capacitor has charged up, the
instantaneous power dissipated by the LTC4267-1 can be
as much as 10W. As the load capacitor charges up, the
power dissipation in the LTC4267-1 will decrease until it
reaches a steady-state value dependent on the DC load
current. The size of the load capacitor determines how fast
the power dissipation in the LTC4267-1 will subside. At
room temperature, the LTC4267-1 can typically handle load
capacitors as large as 800μF without going into thermal
shutdown. With large load capacitors, the LTC4267-1 die
temperature will increase by as much as 50°C during a
single turn-on sequence. If for some reason power were
removed from the part and then quickly reapplied so that
the LTC4267-1 had to charge up the load capacitor again,
the temperature rise would be excessive if safety precau-
tions were not implemented.
The LTC4267-1 PD interface protects itself from thermal
damage by monitoring the die temperature. If the die
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4267IGN-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 |
| LTC4267IGN-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 |
| LTC4268-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4268-1_12 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power PD With Synchronous No-Opto Flyback Controller |
| LTC4268CDKD-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power PD with Synchronous NoOpto Flyback Controller |
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