max5957letnt Maxim Integrated Products, Inc., max5957letnt Datasheet - Page 21

• Manufacturer Part Number: max5957letnt
• Description: Triple Pci Express, Hot-plug Controllers
• Manufacturer: Maxim Integrated Products, Inc.

External capacitance can be added from the gate of
the external MOSFETs to GND to slow down the dV/dt
of the 12V and 3.3V outputs. The maximum gate
capacitance load at 12G_ and 3.3G_ must be consis-
tent with the conditions described in the Setting the
Power-On Reset section.
Large capacitive loads at the 12V output, the 3.3V out-
put, and the 3.3V auxiliary output can cause a problem
when inserting discharged PCI cards into live back-
planes. A fault occurs if the time needed to charge the
capacitance of the board is greater than the typical
startup time (2 x t
stand large capacitive loads due to their adjustable
startup times and adjustable current-limit thresholds.
Calculate the maximum load capacitance as follows:
V
3.3V auxiliary output for slot A, slot B, or slot C.
Table 3. Component Manufacturers
Sense Resistor
MOSFETs
OUT
is either the 3.3V output, the 12V output, or the
Additional External Gate Capacitance
COMPONENT
C
LOAD
FAULT
______________________________________________________________________________________
Maximum Load Capacitance
Triple PCI Express, Hot-Plug Controllers
< (t
). The MAX5957/MAX5958 with-
SU
x I
Vishay-Date
IRC
Fairchild
International Rectifier
Motorola
Vishay-Siliconix
LIM
) / V
MANUFACTURER
OUT
The 12V input (12VIN), the 3.3V input (3.3SA+), and the
3.3V auxiliary (3.3AUXIN) must be above their UVLO
thresholds before startup can occur. Input transients
can cause the input voltage to sag below the UVLO
threshold. The MAX5957/MAX5958 reject transients on
the input supplies that are shorter than 4µs (typ).
Because some load fault conditions can cause voltage
transients to propagate to the supply inputs with dura-
tion of greater than 4µs, it is recommended that a small
Schottky diode be placed in series with the 12VIN pin
connection, upstream of the 1µF bypass capacitor. This
provides a hold-up supply that will prevent the 12VIN
input from dropping below V
sients. See the Typical Application Circuit .
402-564-3131
704-264-8861
888-522-5372
310-322-3331
602-244-3576
PHONE
—
12UVLO
www.mot-sps.com/ppd
www.fairchildsemi.com
www.vishay.com
www.vishay.com
Input Transients
www.irctt.com
www.irf.com
during severe tran-
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