MAX5922BEUI+ Maxim Integrated Products, MAX5922BEUI+ Datasheet - Page 17

• Manufacturer Part Number: MAX5922BEUI+
• Description: IC NETWORK PWR SW +48V 28-TSSOP
• Manufacturer: Maxim Integrated Products
• Type: Power over Ethernet Switch (PoE)r

Specifications of MAX5922BEUI+

• Applications: Remote Peripherals (Industrial Controls, Cameras, Data Access)
• Internal Switch(s): Yes
• Voltage - Supply: 32 V ~ 60 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TSSOP
• On Resistance (max): 0.45 Ohms
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

V
The logic input thresholds of EN, LATCH, CLASS, DCA
(MAX5922A), DET_DIS (MAX5922B/MAX5922C), and
ZC_EN are CMOS compatible and are determined by
the voltage at V
5.5V. The POK, ZC, CL0, CL1, CL2, and FAULT outputs
are open drain. V
are referenced to DGND. DGND is not connected to
AGND internally and must be connected externally at a
single point in the system to AGND. The maximum
allowable difference in the voltage between DGND and
AGND is ±4V.
EN is a logic input to enable the MAX5922. Bringing EN
low halts all operations and turns off the internal power
MOSFET. When EN is high and the input voltage is
above the UVLO threshold, the MAX5922 begins oper-
ating. Enable is also used to unlatch the part after a
latched fault condition. This is done by toggling EN low
and high again after a fault condition.
The MAX5922 provides a sophisticated overcurrent
protection circuitry to ensure the device’s robustness
under output-current transient and current fault condi-
tions. The current protection circuitry employs a con-
stant current limit, a current foldback, and an
overcurrent timeout. The device monitors the voltage
drop, V
load current.
Figure 7. Setting Undervoltage Lockout with an External
Resistive-Divider
DIG
is the input supply for the internal logic circuitry.
SENSE
V
IN
R1
R2
(V
= 32V TO 60V
SENSE
+48V, Single-Port Network Power Switch
DIG
DIG
______________________________________________________________________________________
which can range from 1.65V to
and all logic inputs and outputs
= V
UVLO
Overcurrent Protection
IN
MAX5922
AGND_S
- V
IN
DRAIN
) to determine the
Digital Logic
Enable (EN)
The MAX5922 monitors V
power mode and regulates the current through the
power MOSFET as necessary to keep V
the current-limit sense voltage (V
load-current limit, I
sense resistor, R
(I
than I
ing to draw more than I
constant current source, limiting the output current to
I
timeout, a current-limit fault is generated and the power
MOSFET is turned off (see the Overcurrent Timeout and
Fault Management sections).
While in current-limit condition, the voltage at the OUT
pin drops. As the load resistance reduces (more load-
ing), the output voltage reduces accordingly to main-
tain a constant load current. The power dissipation in
the power MOSFET is (V
output voltage drops lower, more power is dissipated
across the power MOSFET. To reduce this power dissi-
pation, the MAX5922 offers a current foldback feature
where it linearly reduces the V
drops below the OUT current-limit foldback voltage
(V
back limit behavior.
The MAX5922 keeps track of the time it is in current limit.
An internal digital counter begins incrementing its count
at 1count/ms when V
or V
to zero if the current falls back below the current limit.
When the cumulative count reaches 60, an overcurrent
fault is generated. After an overcurrent fault condition, the
switch is turned off and the FAULT signal goes low (see
Figure 9).
Figure 8. Current Foldback Characteristic
LIM
LIM
FBSTOP
. If I
ILIM
= V
LIM
V
ILM
For Power-Over-LAN
V
ILM
/3
OUT
foldback in foldback mode). The counter is reset
, the MOSFET is fully on. When the load is try-
ILIM
= 18V). Figure 8 illustrates this current fold-
is at I
/R
SENSE
V
SENSE
FBSTART
(2V)
LIM
LIM
SENSE
). When the load current is less
, is programmed by the current-
for greater than the current-limit
, connected from IN to DRAIN
LIM
DRAIN
exceeds its limit (either V
SENSE
, the OUT pin works like a
V
FBSTOP
(18V)
Constant Current Limit
ILIM
- V
Overcurrent Timeout
ILIM
at all times during
OUT
Current Foldback
value when V
) × I
= 212mV). The
SENSE
LIM
V
OUT
(max) to
. As the
(V)
OUT
ILIM
17