MAX5945EAX+ Maxim Integrated Products, MAX5945EAX+ Datasheet - Page 17

• Manufacturer Part Number: MAX5945EAX+
• Description: IC NETWORK PWR CTRL 36-SSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX5945EAX+

• Controller Type: Network Power Controller
• Interface: I²C
• Voltage - Supply: 3.3V
• Current - Supply: 4.2mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 4. Foldback Current Characteristics
Connect the gate of the external n-channel MOSFET to
GATE_. An internal 50µA current source pulls GATE_ to
(V
current source pulls down GATE_ to V
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
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.
V
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
(V
DD
EE
SENSE_
V
SU_LIM
supplies power for the internal logic circuitry. V
+ 10V) to turn on the MOSFET. An internal 40µA
V
SU_LIM
- V
GD
EE
/ 3
)
is the total capacitance between GATE and
______________________________________________________________________________________
∆
30V
V
∆
OUT
t
=
MOSFET Gate Driver
I
GATE
C
GD
Quad Network Power Controller
EE
50V
Digital Logic
to turn off the
(V
OUT_
- V
EE
DD
)
digital supply for compatibility with the internal logic.
The MAX5945 also features a V
(V
MAX5945 in reset and the ports shut off. Bit 0 in the
supply event register shows the status of V
(Table 11) after V
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
even higher than AGND (up to 60V). V
be greater than 3.0V when V
When using the AC disconnect detection feature,
AGND must be connected directly to DGND and V
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.
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.
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.
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
keeps the MOSFET off and the MAX5945 in reset until
V
V
when (V
contains an undervoltage lockout (V
AGND
EE
Undervoltage and Overvoltage Protection
DDUVLO
overvoltage (V
- V
for Power-Over-LAN
AGND
) of +1.35V. A V
EE
EE
exceeds 29V for more than 3ms. An internal
undervoltage lockout (V
- V
EE
DD
) exceeds 60V. The digital supply also
EE_OV
has recovered. All logic inputs and
) circuit shuts down the ports
DDUVLO
AGND
DGND
Hardware Shutdown
DD
or V
DDUVLO
undervoltage lockout
≤ (V
condition keeps the
DD
EE
EE
EEUVLO
- V
+ 3.0V)
or at voltages
).
Interrupt
DGND
DDUVLO
) circuit
must
DD
17