参数资料
型号: MAX5952CUAX+
厂商: Maxim Integrated
文件页数: 20/50页
文件大小: 1006K
描述: IC PSE CNTRLR FOR POE 36-SSOP
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 30
类型: 以太网供电控制器(PoE)
应用: 远程外设(工业控制,相机,数据访问)
内部开关:
工作温度: 0°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 36-BSOP(0.295",7.50mm 宽)
供应商设备封装: 36-SSOP
包装: 管件
High-Power, Quad, PSE Controller
for Power-Over-Ethernet
20   ______________________________________________________________________________________
Figure 3a. Foldback Current Characteristics
48V
28V
V
SU_LIM
V
SU_LIM
 / 3
(V
SENSE_
 - V
EE
)
(V
OUT_
 - V
EE
)
Figure 3b. Foldback Current Characteristics for High-Power
Mode
48V
10V
V
SU_LIM
V
SU_LIM
 / 3
(V
RS
 - V
EE
)
(V
OUT_
 - V
EE
)
High-Power Mode
When CL_DISC (R17h[2]) is set to 0, high-power mode
is configured by setting the ICUT bits to any combina-
tion other than 000, 110, or 111 (note that 000 is the
default value for the IEEE standard limit). See Table 3
and the Register Map and Description section.
Foldback Current
During startup and normal operation, an internal circuit
senses the voltage at OUT_ and reduces the current-
limit value when (V
OUT
_ - V
EE
) > 28V. The foldback
function helps to reduce the power dissipation on the
FET. The current limit eventually reduces to 1/3 of I
LIM
when (V
OUT
_ - V
EE
) > 48V (see Figure 3a). For high-
power mode, the foldback starts when (V
OUT
_ - V
EE
) >
10V (see Figure 3b). In high-power mode, the current
limit (I
LIM
) is reduced up to 1/8 of its programmed value
when (V
OUT
_ - V
EE
) > 48V.
MOSFET Gate Driver
Connect the gate of the external n-channel MOSFET to
GATE_. An internal 50礎 current source pulls GATE_ to
(V
EE
+ 10V) to turn on the MOSFET. An internal 40礎
current source pulls down GATE_ to V
EE
to turn off the
MOSFET.
The pullup and pulldown current controls the maximum
slew rate at the output during turn-on or turn-off. Use
the following equation to set the maximum slew rate:
where C
GD
is the total capacitance between GATE and
DRAIN of the external MOSFET. Current limit and the
capacitive load at the drain control the slew rate during
startup. During current-limit regulation, the MAX5952
manipulates the GATE_ voltage to control the voltage at
SENSE_ (V
RS
). A fast pulldown activates if V
RS
over-
shoots the limit threshold (V
SU_LIM
). The fast pulldown
current increases with the amount of overshoot. The
maximum fast pulldown current is 100mA.
During turn-off, when the GATE voltage reaches a value
lower than 1.2V, a strong pulldown switch is activated
to keep the MOSFET securely off.


V
t
I
C
OUT
GATE
GD
=
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