MAX5940CESA+ Maxim Integrated Products, MAX5940CESA+ Datasheet - Page 9

• Manufacturer Part Number: MAX5940CESA+
• Description: IC IEEE 802.3AF PD INTFC 8-SOIC
• Manufacturer: Maxim Integrated Products

Specifications of MAX5940CESA+

• Controller Type: Powered Device Interface Controller (PD)
• Interface: IEEE 802.3af
• Voltage - Supply: 48V
• Current - Supply: 1mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX5940_ charge the gate of the internal MOSFET
with a constant current source (10µA, typ). The drain-
to-gate capacitance of the MOSFET limits the voltage
rise rate at the drain, thereby limiting the inrush current.
Add an external capacitor from GATE to OUT to further
reduce the inrush current. Use the following equation to
calculate the inrush current:
PGOOD is an open-drain, active-high logic output.
PGOOD goes high impedance when V
of V
PGOOD is pulled to V
below GND). Connect PGOOD to the ON pin of a down-
stream DC-DC converter. Connect a 100kΩ pullup resis-
tor from PGOOD to GND if needed.
EE
and when GATE is 5V above V
I
INRUSH
_______________________________________________________________________________________
OUT
PGOOD/
(MAX5940A/MAX5940C only)
=
(given that V
I x
IEEE 802.3af PD Interface Controller
G
Inrush Current Limit
C
C
GATE
OUT
PGOOD Outputs
OUT
OUT
EE
is within 1.2V
. Otherwise,
is at least 5V
For Power-Over-Ethernet
PGOOD is an open-drain, active-low logic output.
PGOOD is pulled to V
and when GATE is 5V above V
goes high impedance. Connect PGOOD to the ON pin of
a downstream DC-DC converter. Connect a 100kΩ
pullup resistor from PGOOD to GND if needed.
During classification mode, if the PSE applies the maxi-
mum DC voltage, the maximum voltage drop from GND
to V
rent of 42mA flows through the MAX5940_, then the maxi-
mum DC power dissipation will be 546mW, which is
slightly higher than the maximum DC power dissipation of
the IC at maximum operating temperature. However,
according to the IEEE 802.3af standard, the duration of
the classification mode is limited to 75ms (max). The
MAX5940_ handle the maximum classification power dis-
sipation for the maximum duration time without sustaining
any internal damage. If the PSE violates the IEEE 802.3af
standard by exceeding the 75ms maximum classification
duration, it may cause internal damage to the IC.
RCLASS
will be 13V. If the maximum classification cur-
EE
when V
(MAX5940B/MAX5940D only)
Thermal Dissipation
OUT
EE
. Otherwise, PGOOD
is within 1.2V of V
EE
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