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| 型号： | LTC4257IS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 3/20页 |
| 文件大小： | 263K |
| 描述： | IC CTRLR INTFACE PWR/ETHER 8SOIC |
| 产品培训模块： | Power over Ethernet |
| 标准包装： | 100 |
| 类型： | 以太网供电开关（PoE） |
| 应用： | IP 电话，LAN 网络供电，网络路由器和交换机 |
| 内部开关： | 是 |
| 电流限制： | 350mA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOIC |
| 包装： | 管件 |
| 产品目录页面： | 1338 (CN2011-ZH PDF) |
LTC4257
3
4257fb
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX UNITS
The ?/SPAN> denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25?/SPAN>C. (Note 3)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All voltages are with respect to GND pin.
Note 3: The LTC4257 operates with a negative supply voltage in the range
of 1.5V to 57V. To avoid confusion, voltages in this data sheet are
always referred to in terms of absolute magnitude. Terms such as
maximum negative voltage refer to the largest negative voltage and a
rising negative voltage refers to a voltage that is becoming more
negative.
Note 4: The LTC4257 is designed to work with two polarity protection
diodes between the PSE and PD. Parameter ranges specified in the
Electrical Characteristics are with respect to LTC4257 pins and are
designed to meet IEEE 802.3af specifications when these diode drops are
included. See Applications Information.
Note 5: Signature resistance is measured via the 2-point V/I method as
defined by IEEE 802.3af. The LTC4257 signature resistance is offset from
25k to account for diode resistance. With two series diodes, the total PD
resistance will be between 23.75k and 26.25k and meet IEEE 802.3af
specifications. The minimum probe voltages measured at the LTC4257
pins are 1.5V and 2.5V. The maximum probe voltages are 8.5V and
9.5V.
Note 6: The LTC4257 includes hysteresis in the UVLO voltages to preclude
any start-up oscillation. Per IEEE 802.3af requirements, the LTC4257 will
power up from a voltage source with 20& series resistance on the first
trial.
Note 7: I
IN_CLASS
does not include classification current programmed at
Pin 2. Total supply current in classification mode will be I
IN_CLASS
+ I
CLASS
(see Note 8).
Note 8: I
CLASS
is the measured current flowing through R
CLASS
.
I
CLASS
accuracy is with respect to the ideal current defined as
I
CLASS
= 1.237/R
CLASS
. The current accuracy specification does not
include variations in R
CLASS
resistance. The total classification current for
a PD also includes the IC quiescent current (I
IN_CLASS
). See Applications
Information.
Note 9: For the DD package, this parameter is assured by design and
wafer level testing.
Note 10: I
OUT_LEAK
includes current drawn at the V
OUT
pin by the power
good status circuit. This current is compensated for in the 25k& signature
resistance and does not affect PD operation.
Note 11: The LTC4257 includes smart thermal protection. In the event of
an overtemperature condition, the LTC4257 will reduce the input current
limit by 50% to reduce the power dissipation in the package. If the part
continues heating and reaches the shutdown temperature, the current is
reduced to zero until the part cools below the overtemperature limit. The
LTC4257 is also protected against thermal damage from incorrect
classification probing by the PSE. If the LTC4257 exceeds the
overtemperature trip point, the classification load current is disabled.
ELECTRICAL CHARACTERISTICS
R
SIGNATURE
Signature Resistance
1.5V d V
IN
d 9.5V, V
OUT
Tied to GND,
?SPAN class="pst LTC4257CS8_2356185_8"> 23.25
26.00
k&
IEEE 802.3af 2-Point Measurement (Notes 4, 5)
V
PG_OUT
Power Good Output Low Voltage
I = 1mA, V
IN
= 48V, PWRGD Referenced to V
IN
?/DIV>
0.5
V
Power Good Trip Point
V
IN
= 48V, Voltage Between V
IN
and V
OUT
(Note 9)
V
PG_THRES_FALL
V
OUT
Falling
?/DIV>
1.3
1.5
1.7
V
V
PG_THRES_RISE
V
OUT
Rising
?/DIV>
2.7
3.0
3.3
V
I
PG_LEAK
Power Good Leakage
V
IN
= 0V, PWRGD FET Off, V
PWRGD
= 57V
?/DIV>
1
礎
R
ON
On-Resistance
I = 300mA, V
IN
= 48V, Measured from V
IN
to V
OUT
1.0
1.6
&
(Note 9)
?/DIV>
2.0
&
I
OUT_LEAK
V
OUT
Leakage
V
IN
= 0V, Power MOSFET Off, V
OUT
= 57V (Note 10) ?/SPAN>
150
礎
I
LIMIT
Input Current Limit
V
IN
= 48V, V
OUT
= 43V (Note 11)
?/DIV>
300
350
400
mA
I
LIMIT_WARM
Overtemperature Input Current Limit
(Note 11)
188
mA
T
OVERTEMP
Overtemperature Trip Temperature
(Note 11)
120
癈
T
SHUTDOWN
Thermal Shutdown Trip Temperature
(Note 11)
140
癈
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4258 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Quad IEEE 802.3at Power over Ethernet Controller |
| LTC4258_09 | 制造商:LINER 制造商全称: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 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 |
| LTC4258CGW#TR | 制造商:Linear Technology 功能描述:POWER OVER ETHERNET CONTROLLER |
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