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参数资料
| 型号： | LTC4267CGN-1#PBF |
| 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： | 11/32页 |
| 文件大小： | 925K |
| 代理商： | LTC4267CGN-1#PBF |
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LTC4267-1
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42671f
APPLICATIO S I FOR ATIO
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Power Good Interface
The
PWRGD signal is controlled by a high voltage, open-
drain transistor. The designer has the option of using this
signal to enable the onboard switching regulator through
the ITH/RUN or the PVCC pins. Examples of active-high
interface circuits for controlling the switching regulator
are shown in Figure 7.
In some applications, it is desirable to ignore intermittent
power bad conditions. This can be accomplished by in-
cluding capacitor C15 in Figure 7 to form a lowpass lter.
With the components shown, power bad conditions less
than about 200μs will be ignored. Conversely, in other
applications it may be desirable to delay assertion of
PWRGD to the switching regulator using C
PVCC or C17
as shown in Figure 7.
It is recommended that the designer use the power
good signal to enable the switching regulator. Using
PWRGD ensures the capacitor C1 has reached within
1.5V of the nal value and is ready to accept a load. The
LTC4267-1 is designed with wide power good hysteresis
to handle sudden uctuations in the load voltage and
current without prematurely shutting off the switching
regulator. Please refer to the Power-Up Sequencing of the
Application Information section.
Signature Disable Interface
To disable the 25k signature resistor, connect SIGDISA pin
to the VPORTP pin. Alternately, SIGDISA pin can be driven
high with respect to VPORTN. An example of a signature
disable interface is shown in Figure 16, option 2. Note that
the SIGDISA input resistance is relatively large and the
threshold voltage is fairly low. Because of high voltages
present on the printed circuit board, leakage currents from
the VPORTP pin could inadvertently pull SIGDISA high. To
ensure trouble-free operation, use high voltage layout
techniques in the vicinity of SIGDISA. If unused, connect
SIGDISA to VPORTN.
Load Capacitor
The IEEE 802.3af specication requires that the PD maintain
a minimum load capacitance of 5μF (provided by C1 in
Figure 11). It is permissible to have a much larger load
capacitor and the LTC4267-1 can charge very large load
capacitors before thermal issues become a problem. The
load capacitor must be large enough to provide sufcient
energy for proper operation of the switching regulator.
However, the capacitor must not be too large or the PD
design may violate IEEE 802.3af requirements.
If the load capacitor is too large, there can be a problem
with inadvertent power shutdown by the PSE. Consider
the following scenario. If the PSE is running at –57V
(maximum allowed) and the PD has detected and powered
up, the load capacitor will be charged to nearly –57V. If
for some reason the PSE voltage is suddenly reduced to
–44V (minimum allowed), the input bridge will reverse
bias and the PD power will be supplied by the load capaci-
tor. Depending on the size of the load capacitor and the
DC load of the PD, the PD will not draw any power for
a period of time. If this period of time exceeds the IEEE
802.3af 300ms disconnect delay, the PSE will remove
power from the PD. For this reason, it is necessary to
ensure that inadvertent shutdown cannot occur.
Very small output capacitors (≤10μF) will charge very
quickly in current limit. The rapidly changing voltage at
the output may reduce the current limit temporarily, caus-
ing the capacitor to charge at a somewhat reduced rate.
Conversely, charging a very large capacitor may cause the
current limit to increase slightly. In either case, once the
output voltage reaches its nal value, the input current
limit will be restored to its nominal value.
The load capacitor can store signicant energy when fully
charged. The design of a PD must ensure that this energy
is not inadvertently dissipated in the LTC4267-1. The po-
larity-protection diode(s) prevent an accidental short on
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4267CGN-1-TR | 制造商:LINER 制造商全称:Linear Technology 功能描述:Power over Ethernet IEEE 802.3af PD Interface with Integrated Switching Regulator |
| LTC4267CGN-1-TRPBF | 制造商:LINER 制造商全称: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 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 |
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