A sense resistor (RS), connected between SENSE_ and
參數(shù)資料
型號(hào)： MAX5945CAX+T
廠商： Maxim Integrated Products
文件頁(yè)數(shù)： 8/44頁(yè)
文件大?。?/td> 0K
描述： IC NETWORK PWR CTRL 36-SSOP
產(chǎn)品培訓(xùn)模塊： Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝： 1,000
控制器類(lèi)型： 網(wǎng)絡(luò)電源控制器
接口： I²C
電源電壓： 3.3V
電流 - 電源： 4.2mA
工作溫度： 0°C ~ 70°C
安裝類(lèi)型： 表面貼裝
封裝/外殼： 36-BSOP（0.295"，7.50mm 寬）
供應(yīng)商設(shè)備封裝： 36-SSOP
包裝： 帶卷 (TR)
MAX5945
Overcurrent Protection
A sense resistor (RS), connected between SENSE_ and
VEE, monitors the load current. Under all circum-
stances, the voltage across RS never exceeds the
threshold VSU_LIM. If SENSE_ exceeds VSU_LIM, an
internal current-limiting circuit regulates the GATE volt-
age, limiting the current to ILIM = VSU_LIM / RS. During
transient conditions, if the SENSE_ voltage exceeds
VSU_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, tSTART, 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 VFLT_LIM = ~88% of VSU_LIM. The tFAULT
counter sets the maximum allowed continuous
overcurrent period. The tFAULT counter increases when
VSENSE exceeds VFLT_LIM and decreases at a slower
pace when VSENSE drops below VFLT_LIM. A slower
decrement for the tFAULT counter allows for detecting
repeated short-duration overcurrents. When the counter
reaches the tFAULT 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
tFAULT. VSU_LIM, is programmable using R27h[4-7].
tFAULT 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 tFAULT 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 tFAULT 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 (VOUT_ - VEE) > 30V. The foldback
function helps to reduce the power dissipation on the
FET. The current limit eventually reduces to 1/3 of ILIM
when (VOUT_ - VEE ) > 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
tDETI
tDETII
tCLASS
150ms
21.3ms
0V
80ms
Figure 3. PGOOD Timing
PGOOD
POK
tPGOOD
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MAX5945EVKIT 功能描述:電源管理IC開(kāi)發(fā)工具 Evaluation Kit/Evaluation System for the MAX5945 RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
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