7
FN4725.5
November 18, 2004
Introduction
The HIP1011D and HIP1011E are the first dual PCI slot IC
devices designed to provide control and protection of the
four PCI power supplies independently to two PCI slots. Like
the widely used HIP1011 this device complies with the PCI
Hot Plug specification facilitating the service, upgrading or
expansion of PCI based servers without the need to power
down the server. The HIP1011D protects against overcurrent
(OC) for the -12V, +12V, +3.3V, +5V and undervoltage (UV)
conditions for the +12V, +3.3V, +5V supplies. The HIP1011E
only responds to OC conditions.
Figure 1 illustrates the typical implementation of the
HIP1011D, HIP1011E. Additional components for optimizing
performance for particular applications, or desired features
may be necessary.
Key Feature Description and Operation
The HIP1011D/E, four power MOSFETs and a few passive
components as configured in Figure 1, create a small yet
complete power control solution for two PCI slots. It provides an
OC trip level greater than the maximum PCI specified current
for each supply to each slot. OC monitoring and protection for
the 3.3V and 5V supplies is provided by sensing the voltage
across external current-sense resistors. For the +12V and -12V
inputs, OC protection is provided internally. On-chip references
in the HIP1011D are used to monitor the +5V, +3.3V and +12V
outputs for UV conditions. During an OC condition on any
output, or a UV condition on the +5V, +3.3V or +12V outputs
(HIP1011D only), all slot specific MOSFETs are immediately
latched-off and a LOW (0V) is presented to the appropriate
FLTN output. During initial power-up of the main V
CC
supply
(+12V), the PWRON
inputs are inhibited from turning on the
switches, and the latch is held in the reset state until the V
CC
input is greater than 10V. After a fault has been asserted and
FLTN is latched low cycling PWRON low then high will clear the
FLTN latch. User programming of the OC thresholds for both
controlled slots is provided by a single resistor connected to the
OCSET pin along with R
SENSE
. In addition delay time to latch
off after a fault condition can be increased by increasing the
FLTN to ground capacitance and the turn-on ramp rate can be
increased by increasing the gate pin capacitance.
Customizing Circuit Performance
OverCurrent (OC) Set Functionality and Resistor
Choice
The HIP1011D/E allows easy custom programming of the
OC levels of all 4 supplies simultaneously for both PCI slots
by simply changing the resistor value between OCSET, (pin
10), and ground. The R
OCSET
value and the OCSET 100A
current source sets a voltage that is used in each of eight
comparators, (one for each supply for both slots). The
voltages developed across the 3.3V and 5V sense resistors
are applied to the inputs of their respective comparators. The
+12V and -12V currents are sensed internally with pilot
devices. Once any comparator trips, that output is fed
through logic circuits resulting in the appropriate FLTN, (pin
4 or pin 11), going low, indicating a fault condition on that
particular slot. Because of the internal current monitoring of
the +12V and -12V switches, their programming flexibility is
limited to R
OCSET
changes. The 3.3V and 5V overcurrent
trip points depend on both R
OCSET
and the value chosen for
each sense resistor.
See Table 1 to determine OC protection levels relative to
choice of R
OCSET
and R
SENSE
values.
Overcurrent design guidelines and recommendations are as
follows:
1. For PCI applications, set R
OCSET
to 6.04k, and use
5m 1% sense resistors (see Figure 24).
2. For non PCI specified applications, the following
precautions and limitations apply:
A. Do not exceed the maximum power of the integrated
NMOS and PMOS. High power dissipation must be
coupled with effective thermal management. The
integrated PMOS has an r
DS(ON)
of 0.3. Thus, with 1A
of steady load current on each of the PMOS devices the
power dissipation is 0.6W. The thermal impedance of the
package is 95 degrees Celsius per watt, limiting the
average DC current on the 12V supply to about 1A on
each slot and imposing an upper limit on the R
OCSET
resistor. Do not use an R
OCSET
resistor greater than
15k.
The average current on the -12V supply should not
exceed 0.7A. Since the thermal restrictions on the +12V
supply are more severe, the +12V supply restricts the use
of the HIP1011 to applications where the 12V supplies
draw relatively little current. Since both supplies only have
one degree of freedom, the value of R
OCSET
, the
flexibility of programming is quite limited. For applications
where more power is required on the +12V supply,
contact your local Intersil sales representative for
information on other Hot Plug solutions.
B. Do not try to sense voltages across the external sense
resistors that are less than 33mV. Spurious faults due to
noise and comparator input sensitivity may result. The
minimum recommended R
OCSET
value is 6k. This will
set the nominal OC voltage thresholds at 52mV and
42mV for the 3.3V and 5V comparators respectively. This
is the voltage level at which the OC fault (I
OUT
x R
SENSE
)
will occur.
C. Minimize V
RSENSE
so as to not significantly reduce the
voltage delivered to the adapter card. Remember PCB
trace and connector distribution voltage losses also need
to be considered. Make sure that the R
SENSE
resistor
can adequately handle the dissipated power. For best
results use a 1% precision resistor with a low temperature
coefficient.
D. Minimize external FET r
DS(ON)
. Low r
DS(ON)
or multiple
MOSFETs in parallel are recommended. See Intersil for a
complete selection of MOSFET offerings.
HIP1011D, HIP1011E
