PI3311-21-LGIZ Datasheet, PDF (22/26 Pages) Vicor Corporation – 8V to 36Vin, 15A Cool-Power ZVS Buck Regulator

equation (3) can be used to calculate R_high values for
the PI3311-X0 regulators.
R _{() (}
)
()
Soft-Start Adjust and Tracking
The TRK pin offers a means to increase the
regulator’s soft-start time or to track with additional
regulators. The soft-start slope is controlled by an
internal capacitor and a fixed charge current to
provide a Soft-Start Time t_SS for all PI33XX-X1
regulators. By adding an additional external
capacitor to the TRK pin, the soft-start time can be
increased further. The following equation can be
used to calculate the proper capacitor for a desired
soft-start times:
(
)
Where, t_TRK is the soft-start time and I_TRK is a 50uA
internal charge current (see Electrical Characteristics
for limits).
There is typically either proportional or direct
tracking implemented within a design. For
proportional tracking between several regulators at
startup, simply connect all devices TRK pins
together. This type of tracking will force all
connected regulators to startup and reach regulation
at the same time (see Figure 5 (a)).
VOUT 1
VOUT 2
(a)
Master VOUT
VOUT 2
(b)
t
Figure 5 - PI33XX-X1 tracking methods
For Direct Tracking, choose the regulator with the
highest output voltage as the master and connect
the master to the TRK pin of the other regulators
vicorpower.com
800 735.6200
PI33XX-X1
through a divider (Figure 6) with the same ratio as
the slave’s feedback divider (see Table 4 for values).
Master VOUT
PI33XX
R1
TRK
Slave
R2
SGND
Figure 6 - Voltage divider connections for direct tracking
All connected regulators’ soft-start slopes will track
with this method. Direct tracking timing is
demonstrated in Figure 5 (b). All tracking regulators
should have their Enable (EN) pins connected
together to work properly.
Inductor Pairing
The PI33XX-X1 utilizes an external inductor. This
inductor has been optimized for maximum efficiency
performance. Table 5 details the specific inductor
value and part number utilized for each PI33XX-X1
device which are manufactured by Eaton.Data sheets
are available at http://www.cooperindustries.com.
Device
PI3311-X1
PI3318-X1
PI3312-X1
PI3301-X1
Inductor
[nH]
85
125
125
150
Inductor
Part Number
FPV1006-85-R
FPV1006-125-R
FPV1006-125-R
FPV1006-150-R
Manufacturer
Eaton
Eaton
Eaton
Eaton
Table 5 - PI33XX-X1 Inductor pairing
Rev 1.3
09/2015
Cool-Power^®
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