max5946aetxt Maxim Integrated Products, Inc., max5946aetxt Datasheet - Page 17

• Manufacturer Part Number: max5946aetxt
• Description: Max5946, Max5946a, Max5946l Dual Pci Express, Hot-plug Controller
• Manufacturer: Maxim Integrated Products, Inc.

A fault occurs when an overcurrent lasts longer then
t
ature condition.
•
•
The MAX5946A automatically restarts from a fault shut-
down after the t
latches off. If an overcurrent fault occurred on a main
output, bring ON_ low for at least t
high again to reset the fault and restart the outputs. If
the overcurrent fault occurred on an auxiliary output or
an overtemperature fault occurred, bring both ON_ and
AUXON_ low for a minimum of t
Bring ON_ and/or AUXON_ high again to restart the
respective outputs. As an extra protection, the
MAX5946L waits a minimum of t
be restarted.
INPUT1 and INPUT2 accept inputs from mechanical
switches. The corresponding outputs are OUTPUT1
and OUTPUT2. OUTPUT_ is debounced for 4ms. When
INPUT_ goes from high to low, OUTPUT_ goes low right
away and stays low for at least 4ms. After the
debounce time OUTPUT_ follows INPUT_. If INPUT_
goes from low to high, OUTPUT_ goes high right away
and stays high for at least 4ms. After the debounce
time, OUTPUT_ follows INPUT_. Figure 5 shows the tim-
ing diagram describing the INPUT_/OUTPUT_
debounced feature.
PRES-DETA and PRES-DETB inputs detect the
PRSNT#2 pin on a PCI express 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
Figure 5. INPUT_ and OUTPUT_ Debounced Feature
FAULT
DEBOUNCED
OUTPUT
A fault on a main output (12V or 3.3V) shuts down
both main outputs of the respective slot. The 3.3V
auxiliary is not affected.
A fault on the 3.3V auxiliary output shuts down all
three outputs of the respective slot.
INPUT
or when the device experiences an overtemper-
Present-Detect and Forced-On Inputs
t
DBC
RESTART
______________________________________________________________________________________
period, while the MAX5946L
Debounced Logic Gate
t
FAULT Management
(Input_ and Output_)
DBC
RESET
( P P R R E E S S - - D D E E T T _ _ , , F F O O N N _ _ )
RESTART
RESET
to reset the fault.
t
DBC
before it can
(100µs) and
Dual PCI Express, Hot-Plug
4ms debounced time. When the card is removed, an
internal 50kΩ pullup forces PRES-DET_ high and the
respective slot is shut down with no delay. PRES-DET_
works in conjunction with ON_ and VAUXON_ and only
enables the device when ON_ and VAUXON_ 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 of the inputs.
Active current limits are provided for all three outputs of
slot A and slot B. 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
R
Circuit. Connect a current-sense resistor between
3.3S_+ and 3.3S_- to set the current limit for the 3.3V
main outputs to 20mV/R
or R4 in the Typical Application Circuit. For the auxiliary
output (3.3V
When the voltage across R
reaches the current-limit threshold voltage, the
MAX5946 regulates the gate voltage to maintain the
current-limit threshold voltage across the sense resis-
tor. If the current limit lasts for t
rent fault occurs. The MAX5946_ shuts down both the
12V and 3.3V outputs and asserts the FAULT_ output of
the respective slot.
When the auxiliary output reaches the current limit
(470mA) for longer then t
device shuts down all outputs and asserts FAULT of the
respective slot.
The UVLO thresholds prevent the internal auxiliary
MOSFETs and the external main channel MOSFETs
(Q1–Q4 in the Typical Application Circuit) from turning
on if V
Internal comparators monitor the main supplies and the
auxiliary supply and keep the gate-drive outputs
(12GA, 12GB, 3.3GA, and 3.3GB) 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 supply is monitored at 3.3SA+ and
has a UVLO threshold of 2.65V. The auxiliary supply is
monitored at 3.3VAUXIN and has a 2.65V UVLO thresh-
old. For either main channel to operate, V
must be above its UVLO threshold.
SENSE12
12VIN
is either R1 or R3 in the Typical Application
AUXO_
, V
Undervoltage Lockout Threshold
3.3VIN
) the current limit is fixed at 470mA.
, and V
SENSE3.3
FAULT
Active Current Limits
3.3VAUXIN
SENSE12
Controller
, a fault occurs and the
FAULT
. R
SENSE3.3
then an overcur-
are not present.
or R
is either R2
3.3VAUXIN
SENSE3.3
SENSE12
17
.