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參數(shù)資料
| 型號(hào)： | MAX5945 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Quad Network Power Controller for Power-Over-LAN |
| 中文描述： | 四路網(wǎng)絡(luò)電源控制器，用于LAN供電 |
| 文件頁數(shù)： | 16/44頁 |
| 文件大小： | 572K |
| 代理商： | MAX5945 |
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M
Overcurrent Protection
A sense resistor (R
S
), connected between SENSE_ and
V
EE
, monitors the load current. Under all circum-
stances, the voltage across R
S
never exceeds the
threshold V
SU_LIM
. If SENSE_ exceeds V
SU_LIM
, an
internal current-limiting circuit regulates the GATE volt-
age, limiting the current to I
LIM
= V
SU_LIM
/ R
S
. During
transient conditions, if the SENSE_ voltage exceeds
V
SU_LIM
, a fast pulldown circuit activates to quickly
recover from the current overshoot. During startup, if
the current-limit condition persists, when the startup
timer, t
START
, times out, the port shuts off and the
STRT_FLT_ bit is set. In normal powered state, the
MAX5945 checks for overcurrent conditions as deter-
mined by V
FLT_LIM
= ~88% of V
SU_LIM
. The t
FAULT
counter sets the maximum allowed continuous
overcurrent period. The t
FAULT
counter increases when
V
SENSE
exceeds V
FLT_LIM
and decreases at a slower
pace when V
SENSE
drops below V
FLT_LIM
. A slower
decrement for the t
FAULT
counter allows for detecting
repeated short-duration overcurrents. When the counter
reaches the t
FAULT
limit, the MAX5945 powers off the
port and asserts the IMAX_FLT_ bit. For a continuous
overstress, a fault latches exactly after a period of
t
FAULT
. V
SU_LIM
, is programmable using R27h[4-7].
t
FAULT
is programmable using R16h[2-3] and R28[4-7].
After power-off due to an overcurrent fault, and if the
RSTR_EN bit is set, the t
FAULT
timer is not immediately
reset but starts decrementing at the same slower pace.
The MAX5945 allows the port to be powered on only
when the t
FAULT
counter is at zero. This feature sets an
automatic duty-cycle protection to the external MOSFET
to avoid overheating. The duty cycle is programmable
using R16h[6-7].
The MAX5945 continuously flags when the current
exceeds the maximum current allowed for the class as
indicated in the CLASS status register. When class
overcurrent occurs, the MAX5945 sets the IVC bit in
register R09h.
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
) > 30V. 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
) > 50V (see Figure 4).
Quad Network Power Controller
for Power-Over-LAN
16
______________________________________________________________________________________
Figure 2. Detection, Classification, and Power-Up Port
Sequence
OUT_
-4V
-9V
-18V
-48V
t
t
DETI
t
DETII
t
CLASS
150ms
150ms
21.3ms
0V
0V
80ms
Figure 3. PGOOD Timing
PGOOD
POK
t
PGOOD
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX5945CAX | Quad Network Power Controller for Power-Over-LAN |
| MAX5945EAX | Quad Network Power Controller for Power-Over-LAN |
| MAX5948 | AND-OR-invert Gates 14-CFP -55 to 125 |
| MAX5948A | -48V Hot-Swap Controllers with External RSENSE |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX5945CAX | 功能描述:熱插拔功率分布 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| MAX5945CAX+ | 功能描述:熱插拔功率分布 IEEE 802.3af Quad Net Pwr Controller RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| MAX5945CAX+T | 功能描述:熱插拔功率分布 IEEE 802.3af Quad Net Pwr Controller RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| MAX5945CAX-T | 功能描述:熱插拔功率分布 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
| MAX5945EAX | 功能描述:熱插拔功率分布 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
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