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參數(shù)資料
| 型號： | LTC4264IDE#PBF |
| 廠商： | Linear Technology |
| 文件頁數(shù)： | 6/24頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC CNTRLR PD INTERFACE 12-DFN |
| 產(chǎn)品培訓(xùn)模塊： | Power over Ethernet |
| 標(biāo)準(zhǔn)包裝： | 91 |
| 控制器類型： | 以太網(wǎng)供電控制器（POE） |
| 接口： | IEEE 802.3af |
| 電流 - 電源： | 3mA |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 12-WFDFN 裸露焊盤 |
| 供應(yīng)商設(shè)備封裝： | 12-DFN（4x3） |
| 包裝： | 管件 |
LTC4264
14
4264f
The active high PWRGD pin features an internal, open-
collector output referenced to VOUT. During inrush, the
active high PWRGD pin pulls low until the load capacitor
is fully charged. At that point, PWRGD becomes high
impedance, indicating the converter may begin running.
The active high PWRGD pin can interface directly with the
“Run” pin of converter products. The PWRGD pin features
an internal 14V clamp to VOUT which protects the DC/DC
converter from excessive voltage. During a power supply
ramp down event, PWRGD becomes low impedance when
VIN drops below the UVLO turn-off threshold, then goes
high impedance when the VIN voltages fall to within the
detection voltage range.
The active low PWRGD pin connects to an internal, open
drain MOSFET referenced to VIN which can sink 1mA.
During inrush, PWRGD is high impedance. Once the load
capacitor is fully charged, PWRGD is pulled low and DC/DC
converter operation can begin. The active low PWRGD
pin can connect directly to the shutdown pin of converter
products. PWRGD is referenced to the VIN pin and when
active will be near the VIN potential. The converter will
typically be referenced to VOUT and care must be taken to
ensure that the difference in potential of the PWRGD pin
does not cause a problem for the DC/DC converter. The
use of diode clamp D9 and RS, as shown in Figure 11,
alleviates any problems.
THERMAL PROTECTION
The LTC4264 includes thermal overload protection in
order to provide full device functionality in a miniature
package while maintaining safe operating temperatures.
At turn-on, before load capacitor C1 has charged up, the
instantaneous power dissipated by the LTC4264 can be
as high as 20W. As the load capacitor charges, the power
dissipation in the LTC4264 will decrease until it reaches
a steady-state value dependent on the DC load current.
The LTC4264 can also experience device heating after
turn-on if the PD experiences a fast input voltage rise. For
example, if the PD input voltage steps from –37V to –57V,
the instantaneous power dissipated by the LTC4264 can
be as high as 16W.
The LTC4264 protects itself from damage by monitoring
die temperature. If the die exceeds the overtemperature
trip point, the power MOSFET and classication transis-
tors are disabled until the part cools down. Once the die
cools below the overtemperature trip point, all functions
are enabled automatically.
During classication, excessive heating of the LTC4264
can occur if the PSE violates the 75ms probing time limit.
In addition, the IEEE 802.3af specication requires a PD
to withstand application of any voltage from 0V to 57V
indenitely. To protect the LTC4264 in these situations,
the thermal protection circuitry disables the classication
circuit if the die temperature exceeds the overtemperature
trip point. When the die cools down, classication current
is enabled.
Once the LTC4264 has charged up the load capacitor
and the PD is powered and running, there will be some
residual heating due to the DC load current of the PD
owing through the internal MOSFET. In some high cur-
rent applications, the LTC4264 power dissipation may be
signicant. The LTC4264 uses a thermally enhanced DFN12
package that includes an Exposed Pad which should be
soldered to an electrically isolated heat sink on the printed
circuit board.
MAXIMUM AMBIENT TEMPERATURE
The LTC4264 ILIM_EN pin allows the PD designer to disable
the normal operating current limit. With the normal cur-
rent limit disabled, it is possible to pass currents as high
as 1.4A through the LTC4264. In this mode, signicant
package heating may occur. Depending on the current,
voltage, ambient temperature, and waveform character-
istics, the LTC4264 may shut down. To avoid nuisance
trips of the thermal shutdown, it may be necessary to
limit the maximum ambient temperature. Limiting the die
temperature to 125°C will keep the LTC4264 from hitting
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| LTC4265 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4265CDE#PBF | 功能描述:IC CTRLR PD INTERFACE HP 12-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 標(biāo)準(zhǔn)包裝:50 系列:- 類型:熱交換控制器 應(yīng)用:-48V 遠(yuǎn)程電力系統(tǒng)，AdvancedTCA ? 系統(tǒng)，高可用性 內(nèi)部開關(guān):無 電流限制:可調(diào) 電源電壓:11.5 V ~ 14.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:10-MSOP 包裝:管件 |
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