max5957letnt Maxim Integrated Products, Inc., max5957letnt Datasheet - Page 18

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

Triple PCI Express, Hot-Plug Controllers
INPUT1, INPUT2, and INPUT3 accept inputs from
mechanical switches. The corresponding outputs are
OUTPUT1, OUTPUT2, and OUTPUT3. OUTPUT_ is
debounced for 4ms. When INPUT_ goes from high to
low, OUTPUT_ goes low immediately and stays low for
at least 4ms. After the debounce time, OUTPUT_ fol-
lows INPUT_. If INPUT_ goes from low to high, OUT-
PUT_ goes high immediately and stays high for at least
4ms. After the debounce time, OUTPUT_ follows
INPUT_. Figure 5 shows the timing diagram describing
the INPUT_/OUTPUT_ debounced feature.
PRES-DET_ input detects the PRSNT#2 pin on a PCIe
connector. When the card is plugged in, PRES-DET_
goes low and allows the turn-on of the outputs of the
respective slot after a 4ms debounced time. When the
card is removed, an internal 50kΩ pullup resistor forces
PRES-DET_ high and the respective slot is shut down
with no delay. PRES-DET_ works in conjunction with
ON_ and AUXON_ and only enables the device when
ON_ and AUXON_ are high.
A logic-low on FON_ forces the respective slot (main
supplies and auxiliary) to turn on regardless of the sta-
tus of the other logic inputs, provided the UVLO thresh-
olds are exceeded on all the inputs.
Figure 5. INPUT_ and OUTPUT_ Debounced Feature
18
DEBOUNCED
OUTPUT
______________________________________________________________________________________
INPUT
Present-Detect and Forced-On Inputs
t
DBC
(INPUT_ and OUTPUT_)
Debounced Logic Gate
t
DBC
(PRES-DET_, FON_)
t
DBC
Active current limits are provided for all three outputs of
the three slots (slot A, slot B, and slot C). Connect a
current-sense resistor between 12S_+ and 12S_- to set
the current limit for the 12V outputs. The current limit is
set to 54mV / R
tor between 3.3S_+ and 3.3S_- to set the current limit
for the 3.3V main outputs to 20mV / R
auxiliary output (3.3VAUXO_) the current limit is fixed at
450mA in the MAX5957 and 700mA in the case of the
MAX5958.
When the voltage across R
reaches the current-limit threshold voltage, the
MAX5957/MAX5958 regulate the gate voltage to main-
tain the current-limit threshold voltage across the sense
resistor. If the current limit lasts for t
overcurrent fault occurs. The MAX5957/MAX5958 shut
down both the 12V and 3.3V outputs and assert the
FAULT_ output of the respective slot.
When the auxiliary output reaches the current limit for
longer than t
down all outputs and asserts FAULT of the respective slot.
The UVLO thresholds prevent the internal auxiliary
MOSFETs and the external main channel MOSFETs
from turning on if V
not present. Internal comparators monitor the main
supplies and the auxiliary supply and keep the gate-
drive outputs (12GA, 12GB, 12GC, 3.3GA, 3.3GB, and
3.3GC) low until the supplies rise above their UVLO
threshold. The 12V main supply is monitored at 12VIN
and has a UVLO threshold of 10V. The 3.3V main sup-
ply is monitored at 3.3SA+ and has a UVLO threshold
of 2.65V. The auxiliary supply is monitored at
3.3AUXIN and has a 2.65V UVLO threshold. For either
main channels to operate, V3.3AUXIN must be above
its UVLO threshold.
FAULT
SENSE12
, a fault occurs and the device shuts
12VIN
. Connect a current-sense resis-
, V
Active Current Limits
3.3VIN
SENSE12
, and V
UVLO Threshold
SENSE3.3
FAULT
or R
3.3VAUXIN
SENSE3.3
, then an
. For the
are