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| 型号： | MAX5965AEAX+ |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 电源管理 |
| 英文描述： | High-Power, Quad, Monolithic, PSE Controllers for Power over Ethernet; Package: SSOP;36 pin;163 mm² ; Temperature: -40°C to +85°C |
| 中文描述： | 4-CHANNEL POWER SUPPLY MANAGEMENT CKT, PDSO36 |
| 封装： | ROHS COMPLIANT, SSOP-36 |
| 文件页数： | 14/54页 |
| 文件大小： | 1525K |
| 代理商： | MAX5965AEAX+ |
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MAX5965A/MAX5965B
High-Power, Quad, Monolithic, PSE Controllers
for Power over Ethernet
______________________________________________________________________________________
21
Overcurrent Protection
A sense resistor RS connected between SENSE_ and
VEE monitors the load current. Under normal operating
conditions, the voltage across RS (VRS) never exceeds
the threshold VSU_LIM. If VRS 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 VRS exceeds VSU_LIM by more
than 1V, 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 the normal powered state, the
MAX5965A/MAX5965B check for overcurrent condi-
tions as determined by VFLT_LIM = ~88% of VSU_LIM.
The tFAULT counter sets the maximum allowed continu-
ous overcurrent period. The tFAULT counter increases
when VRS exceeds VFLT_LIM and decreases at a slower
pace when VRS drops below VFLT_LIM. A slower decre-
ment for the tFAULT counter allows for detecting repeat-
ed short-duration overcurrents. When the counter
reaches the tFAULT limit, the MAX5965A/MAX5965B
power off the port and assert the IMAX_FLT_ bit. For a
continuous overstress, a fault latches exactly after a
period of tFAULT. VSU_LIM is programmable through the
ICUT registers R2Ah[6:4], R2Ah[2:0], R2Bh[6:4],
R2Bh[2:0], and the IVEE bits in register R29h[1:0]. See
the
High-Power Mode section for more information on
the ICUT register.
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 MAX5965A/MAX5965B allow the port to be pow-
ered on only when the tFAULT counter is at zero. This
feature sets an automatic duty-cycle protection to the
external MOSFET avoiding overheating.
The MAX5965A/MAX5965B continuously flag when the
current exceeds the maximum current allowed for the
class as indicated in the CLASS status register. When
class overcurrent occurs, the MAX5965A/MAX5965B
set the IVC_ bit in register R09h.
ICUT Register and High-Power Mode
ICUT Register
The ICUT register determines the maximum current lim-
its allowed for each port of the MAX5965A/MAX5965B.
The 3 ICUT bits (R2Ah[6:4], R2Ah[2:0], R2Bh[6:4], and
R2Bh[2:0]) allow programming of the current-limit and
overcurrent thresholds in excess of the IEEE standard
limit (see Tables 34a, 34b, and 34c). The ICUT regis-
ters can be written to directly through the I2C interface
when CL_DISC (R17h[2]) is set to 0 (see Table 3). In
this case, the current limit of the port is configured
regardless of the status of the classification.
By setting the CL_DISC bit to 1, the MAX5965A/
MAX5965B automatically set the ICUT register based
upon the classification result of the port. See Table 3
and the
Register Map and Description section.
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 (VOUT_ - VEE) > 28V. The foldback
function helps to reduce the power dissipation on the
FET. The current limit eventually reduces down to 1/3 of
ILIM when (VOUT_ - VEE ) > 48V (see Figure 3a). For
high-power mode, the foldback starts when (VOUT_ -
VEE ) > 10V (see Figure 3b). In high-power mode, the
current limit (ILIM) is reduced down to minimum fold-
back current (VTH_FB/RS) when (VOUT_ - VEE ) > 48V.
Figure 2. PGOOD_ Timing
PGOOD_
POK_
tPGOOD
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| MAX5965AEAX+ | 功能描述:热插拔功率分布 Quad PSE Controller for POE RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5965AEAX+T | 功能描述:热插拔功率分布 Quad PSE Controller for POE RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5965AUAX+ | 功能描述:热插拔功率分布 Quad PSE Controller for POE RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5965AUAX+T | 功能描述:热插拔功率分布 Quad PSE Controller for POE RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5965BCAX+ | 制造商:Maxim Integrated Products 功能描述:- Rail/Tube |
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