ISL6112 Datasheet, PDF (24/31 Pages) Intersil Corporation – Dual Slot PCI-Express Power Controller

ISL6112
PCI-Express Application
Recommendations
For each of the 3.3VMAIN and +12VMAIN supplies, the CR
level is set by an external sense resistor value depending on
the maximum specified power for the various PCI-Express
connector and application implemented (X1, 10W or 25W;
X4, X8, 25W; X16, 25W or 75W; and X16 Graphics -ATX,
150W). The power rating is a combination of both main and
the optional auxiliary supplies. This sense resistor is a low
ohmic standard value current sense resistor (one for each
slot) and the voltage across this resistor is compared to a
50mV reference. Since the 3.3VMAIN supply is rated for 3A
max across all slots regardless of size and power, the use of
a 15mΩ sense resistor compared to the 50mV reference
provides a nominal CR of 3.3A or 11% above the 3A max
spec.
On the 12VMAIN, for a 10W connector, a 75mΩ sense
resistor provides a nominal CR level of 0.66A, 32% above
the 0.5A max spec; for a 25W connector, a 20mΩ sense
resistor provides a nominal CR level of 2.5A, 19% above the
2.1A max specification; for a 75W connector a 8mΩ sense
resistor provides a nominal CR level of 6.25A, 14% above
the 5.5A max specification. The X16 Graphics-ATX 150W
card is a special case in that, the 150W is provided by 2
slots, each providing up to a maximum of 75W from the
12VMAIN as this type of card does not consume 3.3VMAIN
or AUX supply power. For each of the slots a 7mΩ sense
resistor provides a nominal CR level of 7.1A, 14% above the
6.25A max spec.
The ISL6112 provides a best in class ±5% current regulation
threshold spec over temperature for the MAIN supples
providing the highest accuracy and lowest variability for this
critical parameter. Table 10 provides recommended
12VMAIN sense resistor values for particular power levels.
TABLE 10.
NOMINAL CURRENT REGULATION LEVEL
12VMAIN R_SENSE 12VMAIN PCI-E ADD IN BOARD POWER
(mΩ)
CR (A)
LEVEL SUPPORTED (W)
75
0.7
10
20
2.5
25
8
6.2
75
7
7
150
NOTE: CR Level = VTH_ILIMIT/R_SENSE.
Providing a nominal CR protection level above the maximum
specified limits of the card ensures that the card is able to
draw its maximum specified loads, and, in addition has
enough headroom before a regulated current limiter is
invoked to protect against transients and other events. This
headroom margin can be adjusted up or down by utilizing
differing values of sense resistor.
Using the ISL6112EVAL1Z Platform
Description and Introduction
The primary ISL6112 evaluation platform is shown in
Figure 34 photographically and schematically on page 28.
This evaluation board highlights a PCB layout that confines
all necessary active and passive components in an area
measuring 12mmx55mm. This width is smaller than the
specified PCI-Express socket to socket spacing, allowing for
intimate co-location of the load power control and the load
itself.
Around the central highlighted layout are numerous labeled
test points and configuration jumpers where there are node
names such as AO(L/R). The pin name outside the
parentheses relates to the ISL6112. The ISL6113 and
ISL6114 also use this evaluation platform as all three parts
have a common pinout for the common pin functions. The
pin names in parentheses are for them. The specific
evaluation board as ordered and received will reflect the part
number in the area below the Intersil logo either by label or
silk screened lettering. For those pins not common across
the ISL6112 and ISL6113, ISL6114, there is a matrix
detailing the differences in the bottom left corner.
The ISL6112EVAL1Z is default provided in HPI mode with
the clock shorted to ground.
After correctly biasing the evaluation platform as noted
through the 6 banana jacks, on VSTBY first then the other
MAIN supplies, in any order. With the appropriate signaling
to the AUXEN and ON inputs, the user should see turn-on
waveforms as shown previously. The addition of external
current loading is necessary to demonstrate the OC and
WOC response performance.
For demonstration of SMI operation the SCL and SDA inputs
are in the top right quadrant of the evaluation board. The
board’s default address is configured as ‘000’ via three
jumpers located to the right labeled A0, A1, and A2. The HPI
inputs need to be disabled as shown in Figure 1. Additional
software to configure and control is needed. If necessary,
there is a LabView based program available from the factory
for demonstration of the ISL6112 functionality. User lab test
hardware and instrument support is not available.
Caution: The ISL6113EVAL1Z, ISL6114EVAL1Z get very hot
to the touch after operating it for a few minutes. The hottest
areas are marked on the evaluation board.
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FN6456.0
September 28, 2007