參數(shù)資料
型號(hào)： MAX5945CAX
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類(lèi)： 電源管理
英文描述： Quad Network Power Controller for Power-Over-LAN
中文描述： 4-CHANNEL POWER SUPPLY MANAGEMENT CKT, PDSO36
封裝： 0.80 MM PICTH, SSOP-36
文件頁(yè)數(shù)： 17/44頁(yè)
文件大?。?/td> 572K
代理商： MAX5945CAX
MOSFET Gate Driver
Connect the gate of the external n-channel MOSFET to
GATE_. An internal 50μA current source pulls GATE_ to
(V
EE
+ 10V) to turn on the MOSFET. An internal 40μA
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. The
pullup current (gate-charging current) is programmable
using R23h[5-7]. Use the following equation to set the
maximum slew rate:
where C
GD
is the total capacitance between GATE and
DRAIN of the external FET. Current limit and the capac-
itive load at the drain control the slew rate during start-
up. During current-limit regulation, the MAX5945
manipulates the GATE_ voltage to control the voltage at
SENSE_. A fast pulldown activates if SENSE_ over-
shoots the limit threshold. 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 FET securely off.
Digital Logic
V
DD
supplies power for the internal logic circuitry. V
DD
ranges from +1.71V to +3.7V and determines the logic
thresholds for the CMOS connections (SDAIN,
SDAOUT, SCL, AUTO,
SHD_
, A_). This voltage range
enables the MAX5945 to interface with a nonisolated
low-voltage microcontroller. The MAX5945 checks the
digital supply for compatibility with the internal logic.
The MAX5945 also features a V
DD
undervoltage lockout
(V
DDUVLO
) of +1.35V. A V
DDUVLO
condition keeps the
MAX5945 in reset and the ports shut off. Bit 0 in the
supply event register shows the status of V
DDUVLO
(Table 11) after V
DD
has recovered. All logic inputs and
outputs reference to DGND. DGND and AGND are
completely isolated internally to the MAX5945. In a
completely isolated system, the digital signal can be
referenced indifferently to V
AGND
or V
EE
or at voltages
even higher than AGND (up to 60V). V
DD
- V
DGND
must
be greater than 3.0V when V
DGND
≤
(V
EE
+ 3.0V)
When using the AC disconnect detection feature,
AGND must be connected directly to DGND and V
DD
must be greater than +3V. In this configuration, con-
nect DGND to AGND at a single point in the system as
close to MAX5945 as possible.
Hardware Shutdown
SHD_
shuts down the respective ports without using
the serial interface. Hardware shutdown offers an emer-
gency turn-off feature that allows a fast disconnect of
the power supply from the port. Pull
SHD_
low to
remove power.
Interrupt
The MAX5945 contains an open-drain logic output (
INT
)
that goes low when an interrupt condition exists. R00h
and R01h (Tables 5 and 6) contain the definitions of the
interrupt registers. The mask register R01h determines
events that trigger an interrupt. As a response to an
interrupt, the controller reads the status of the event reg-
ister to determine the cause of the interrupt and takes
subsequent actions. Each interrupt event register also
contains a clear-on-read (CoR) register. Reading
through the CoR register address clears the interrupt.
INT
remains low when reading the interrupt through the
read-only addresses. For example, to clear a startup
fault on port 4 read address 09h (see Table 10). Use the
global pushbutton bit on register 1Ah (bit 7, Table 22) to
clear interrupts, or use a software or hardware reset.
Undervoltage and Overvoltage Protection
The MAX5945 contains several undervoltage and over-
voltage protection features. Table 11 in the
Register Map
and Description
section shows a detailed list of the
undervoltage and overvoltage protection features. An
internal V
EE
undervoltage lockout (V
EEUVLO
) circuit
keeps the MOSFET off and the MAX5945 in reset until
V
AGND
- V
EE
exceeds 29V for more than 3ms. An internal
V
EE
overvoltage (V
EE_OV
) circuit shuts down the ports
when (V
AGND
- V
EE
) exceeds 60V. The digital supply also
contains an undervoltage lockout (V
DDUVLO
).
V
t
I
C
OUT
GATE
GD
=
M
Quad Network Power Controller
for Power-Over-LAN
______________________________________________________________________________________
17
Figure 4. Foldback Current Characteristics
50V
30V
V
SU_LIM
V
SU_LIM
/ 3
(V
SENSE_
- V
EE
)
(V
OUT_
- V
EE
)
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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 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
MAX5945EAX+ 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
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