ISL6113 Datasheet, PDF (10/24 Pages) Intersil Corporation – Dual Slot PCI-E Hot Plug Controllers

ISL6113, ISL6114
ISL6113, ISL6114 Descriptions and
Operational Explanation
These two ICs target the dual PCI-EXPRESS slot
application for add-in cards in servers. Together with a pair
of N and P-Channel MOSFETs, four high precision current
sense resistors and a handful of passive components, the
ISL6113, ISL6114 provide a PCI-E compliant hot plug control
solution. These ICs use the Hot Plug Interface (HPI) for
communicating, enabling, monitoring and reporting of UV
conditions and OC and over temperature faults. Additionally
they have a full complement of PCI-E specific I/O.
The ISL6113, ISL6114 share the same footprint as their
sister part, the ISL6112, which features both SMI and HPI
control and communication capabilities, neither of these two
has serial bus capabilities. Whereas the ISL6113 has the
same turn-on characteristics as the ISL6112, the ISL6114
uses a lower level of current sourcing on the GATE outputs
(5µA vs the ISL6113’s 25µA). This lower sourcing current
allows the user to use less GATE capacitance for in-rush
current and GATE ramp control than the ISL6113 to achieve
similar turn-on characteristics. This reduced capacitance in
turn provides for a faster turn-off of the MAIN supplies by the
ISL6114 in the event of an OC fault than is possible with the
ISL6113.
Bias, Power-On Reset and Power Cycling
The ISL6113, ISL6114 utilizes the VSTBY pins as the only IC
bias supply source. For systems without a dedicated 3.3V
auxiliary supply, the 3VMAIN supply is to be used for the IC
bias. A Power-On Reset (POR) cycle is initiated after VSTBY
rises above its UVLO threshold and remains satisfied for
t_POR, ~250µs. If VSTBY is recycled, the ISL6113, ISL6114
enters a new power-on-reset cycle. VSTBY must be the first
supply voltage applied followed by the MAIN supply inputs.
During t_POR, all outputs remain off. PCI-Express (PCI-E)
compliance requires that the connector power must be off
prior to and during insertion and during removal of a PCI-E
board. Before the add-in board is properly inserted into or
removed from a connector, the FET switches are turned off
via the enabling inputs (ON_X and AUXEN_X). In the event
of an improper insertion or removal and to ensure that the
power is off when necessary, the ISL6113, ISL6114 has a
present input (PRSNT) per slot that overrides and disables
the enabling inputs if PRSNT is not pulled low by having a
card fully inserted into the slot to complete the pull-down
circuit. The PRSNT pin must be a last to make, first to break
connection to ensure compliance.
Enabling the VAUX Outputs
Upon asserting an AUXEN input, the related output turns-on
the internal power switch between the VSTBY supply and its
load. The turn-on is slew rate limited and invokes the ICs
current regulation feature so as to not droop the supply due
to in-rush current loading. Figure 2 illustrates the ISL6113
AUX turn-on performance into a 100Ω, 150µF load with the
in-rush load current being limited to ~1A.
.
VAUX
AUXEN
IAUX
FIGURE 2. VAUX TURN-ON R_LOAD = 10Ω, C_LOAD = 100µF
Standby Mode
Standby mode is entered when one or more of the MAIN
supply inputs (12V_IN and/or 3V_IN) is absent, below its
respective UVLO threshold or OFF. The ISL6113, ISL6114
also has 3.3V auxiliary outputs (VAUX), satisfying an
optional PCI Express requirement. These outputs are fed
from the VSTBY input pins and controlled by the AUXEN
input pins and are independent of the MAIN outputs. Should
IC be in standby mode the VAUX switch will function as long
as V_VSTBY is compliant. Prior to standby mode, ONA and
ONB inputs must be deasserted or else the ISL6113,
ISL6114 will assert its FAULT outputs.
Enabling the MAIN GATE Outputs
The related AUXEN must be active for the MAIN supplies to
be enabled otherwise they will be latched off. When a slots
MAIN supplies are off, the 12VGATE pin is held high with an
internal pull-up to the 12VIN voltage. Similarly, the 3VGATE
pin is internally held low to GND. With an add-in card
properly in place, when an ON_X pin is signaled high, the
ISL6113, ISL6114 enables control of one slot turning on one
pair of FETs via the 3VGATE and 12VGATE pins. The FET
gates are charged with a +25µA (+5µA for the ISL6114)
current sink/source pulling the 12VGATE pin to ground and
the 3VGATE pin is charged to ~12VIN thereby enhancing
both of the MAIN supply FET switches.
Estimating In-Rush Current and V_OUT Slew Rate at
Start-Up
The expected in-rush current can be estimated by using
Equation 1:
ISL6113 -
I_INRUSHNominally
=
25
μ
A
⎛
⎜
⎝
CC_{-----LG---O--A---AT----DE--⎠⎟⎞}
ISL6114 -
I_INRUSHNominally
=
5μA
⎛
⎜
⎝
CC_{-----LG---O--A---AT----DE--⎠⎟⎞}
(EQ. 1)
With 25µA and 5µA being the GATE pin charge current for
10
FN6457.0
September 25, 2007