MAX5981AETE+ Maxim Integrated Products, MAX5981AETE+ Datasheet - Page 12

• Manufacturer Part Number: MAX5981AETE+
• Description: Power Switch ICs - POE / LAN IEEE 802.3af/at PDIC Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX5981AETE+

• Lead Free Status / Rohs Status: Details

IEEE 802.3af/at-Compliant, Powered Device Interface
Controllers with
Type 2 PSE detection flag. Alternatively, the 2EC output
also serves as a wall adapt er detection output when the
MAX5981A/MAX5981B are powered by an external wall
power adapter. See the Wall Power Adapter Detection
and Operation section for more information.
The MAX5981A/MAX5981B enter power mode when V
rises above the undervoltage lock out threshold (V
When V
turn on the internal n-channel isolation MOSFET to con-
nect V
to 135mA (typ). The iso lation MOSFET is fully turned on
when the voltage at RTN is near V
rent is reduced below the inrush limit. Once the isolation
MOSFET is fully turned on, the MAX5981A/MAX5981B
change the cur rent limit to 800mA. The open-drain
power-good output (PG) remains low for a minimum of
t
downstream DC-DC converter disabled during inrush.
The MAX5981A/MAX5981B operate up to a 60V supply
voltage with a turn-on UVLO threshold (V
and a turn-off UVLO threshold (V
input voltage is above V
enter power mode and the inter nal MOSFET is turned on.
When the input voltage goes below V
t
The MAX5981A/MAX5981B feature a sleep mode, which
pulls PG low while keeping the internal n-channel isola-
tion MOSFET turned on. The PG output is used to dis-
able downstream DC-DC converters reducing the power
consumption of the overall PD system in sleep mode. In
sleep mode, the LED driver output (LED) sources peri-
odic current pulses. The LED current I
external resistor R
section for more information.
An ultra-low-power sleep mode allows the MAX5981A/
MAX5981B to further reduce power consumption while
maintaining the power signature of the standard. The
ultra-low-power enable input ULP is internally held high
with a 50kI pullup resistor to the internal 5V bias of the
MAX5981A/MAX5981B. Set ULP to logic-low and apply a
falling edge to SL to enable ultra-low-power sleep mode.
Apply a falling edge on the wake-mode enable input
(WK) to disable sleep or ultra-low-power sleep mode and
resume normal operation.
12
DELAY
OFF_DLY
_____________________________________________________________________________________
SS
until the power MOSFET fully turns on to keep the
IN
, the MOSFET turns off.
to RTN with inrush current limit internally set
rises above V
Sleep and Ultra-Low-Power Sleep Modes
SL
, see the Applications Information
ON
ON
, the MAX5981A/MAX5981B
Undervoltage Lockout
, the MAX5981A/MAX5981B
Power Mode (Wake Mode)
OFF
SS
Integrated Power MOSFET
and the inrush cur-
) at 31V. When the
OFF
LED
for more than
ON
is set by an
) at 35.4V
ON
IN
).
The MAX5981A/MAX5981B drive an LED connected
from the output LED to V
power sleep mode, the LED is driven by current pulses
with the amplitude set by the resistor connected from SL
to V
mable from 10mA to 20mA using R
following formula:
An open-drain output (PG) is used to allow disabling
downstream DC-DC converter until the n-channel isola-
tion MOSFET is fully turned on. PG is pulled low to V
for a period of t
MOSFET is fully turned on. The PG is also pulled low
during sleep mode and coming out of thermal shutdown.
The MAX5981A/MAX5981B include thermal protection
from excessive heating. If the junction tempera ture
exceeds the thermal-shutdown threshold of +140NC,
the MAX5981A/MAX5981B turn off the internal power
MOSFET, LED driver, and 2EC current sink. When the
junction temperature falls below +112NC, the device
enters inrush mode and then return to power mode.
Inrush mode ensures the downstream DC-DC converter
is turned off as the internal power MOSFET is turned on.
For applications where an auxiliary power source such
as a wall power adapter is used to power the PD,
the MAX5981A/MAX5981B feature wall power adapter
detection. The MAX5981A/MAX5981B give highest prior-
ity to the WAD and smooth ly switch the power supply to
WAD when it is detected. Once the input voltage (V
V
MAX5981B enable wall adapter detection. The wall
power adapt er is connected from WAD to RTN. The
MAX5981A/MAX5981B detect the wall power adapter
when the voltage from WAD to RTN is greater than 9V.
When a wall power adapter is detected, the internal
n-channel isolation MOSFET turns off, 2EC current sink
turns on, and classification current is disabled if V
the classification range.
Wall Power Adapter Detection and Operation
SS
) exceeds the mark event threshold, the MAX5981A/
SS
. The LED driver current ampli tude is program-
I
LED
=
DELAY
Thermal-Shutdown Protection
R
SL
645.75
+
SS
1200
and until the internal isolation
. During sleep mode/ultra-low-
(in amperes)
Power-Good Output
SL
according to the
LED Driver
IN
DD
is in
SS
-