MAX5909EEE Maxim Integrated Products, MAX5909EEE Datasheet - Page 11

• Manufacturer Part Number: MAX5909EEE
• Description: Hot Swap & Power Distribution
• Manufacturer: Maxim Integrated Products

Specifications of MAX5909EEE

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Figure 2. Startup Waveforms
The slow comparator is disabled during the startup
period while the external MOSFETs are turning on.
Disabling the slow comparator allows the device to
ignore the higher-than-normal inrush current charging
the board capacitors when a card is first plugged into a
live backplane.
After the startup period is complete the slow compara-
tor is enabled and the device enters normal operation.
The comparator threshold voltage (V
25mV for the MAX5904/MAX5905 and is adjustable
from 25mV to 100mV for the MAX5906–MAX5909. The
slow-comparator response time decreases to a mini-
mum of 110µs with a large overdrive voltage (Figure 9).
Response time is 3ms for a 1mV overdrive. The variable
speed response time allows the MAX5904–MAX5909 to
ignore low-amplitude momentary glitches, thus increas-
ing system noise immunity. After an extended overcur-
rent condition, a fault is generated, PGOOD is pulled
low, and the MOSFET gates are discharged with a
strong 3mA pulldown current.
During the startup period the fast comparator regulates
the gate voltage to ensure that the voltage across the
sense resistor does not exceed V
Low-Voltage, Dual Hot-Swap Controllers/Power
PGOOD
I
V
V
LOAD
GATE
OUT
ON
V
R
SU,TH
SENSE
Slow-Comparator Normal Operation
______________________________________________________________________________________
Slow-Comparator Startup Period
Fast-Comparator Startup Period
t
ON
V
TH
t
START
+ t
PGDLY
4.8V TO 5.8V
C
C
BOARD
BOARD
SU,TH
SC,TH)
= LARGE
= 0
. The startup
is fixed at
V
V
GATE
OUT
fast-comparator threshold voltage (V
two times the slow-comparator threshold (V
In normal operation, if the load current reaches the fast-
comparator threshold, a fault is generated, PGOOD is
pulled low, and the MOSFET gates are discharged with
a strong 3mA pulldown current. This happens in the
event of a serious current overload or a dead short. The
fast-comparator threshold voltage (V
four times the slow-comparator threshold (V
comparator has a fast response time of 260ns (Figure 9).
The undervoltage lockout prevents the MAX5904–
MAX5909 from turning on the external MOSFETs until
one input voltage exceeds the UVLO threshold (2.4V)
for t
the higher input voltage rail for the charge pumps. This
allows for more efficient charge-pump operation. The
UVLO protects the external MOSFETs from an insuffi-
cient gate drive voltage. t
is fully inserted into the backplane and that the input
voltages are stable. Any input voltage transient on both
supplies below the UVLO threshold will reinitiate the
t
The MAX5905/MAX5907/MAX5909 latch the external
MOSFETs off when a fault is detected. Toggling ON
below 0.4V or one of the supply voltages below the
UVLO threshold for at least 100µs clears the fault latch
and reinitiates the startup period. Similarly, the
MAX5904/MAX5906/MAX5908 turn the external
MOSFETs off when a fault is detected then automatical-
ly restart after the autoretry delay that is internally set to
64 times t
ON below 0.4V does not clear the fault. The autoretry
can be overridden causing the startup period to begin
immediately by toggling one of the supply voltages
below the UVLO threshold.
D,UVLO
Latched and Autoretry Fault Management
D,UVLO
and the startup period.
START
. The MAX5904–MAX5909 use power from
. During the autoretry delay, toggling
Undervoltage Lockout (UVLO)
Fast-Comparator Normal Operation
D,UVLO
Sequencers
ensures that the board
FC,TH
SU,TH
) is scaled to
) is scaled to
SC,TH
SC,TH
).
). This
11