Application Note 1789
3. To avoid noise coupling, we recommend adding 1nF
Phase-shift Programming
capacitors on all COMP and ISHARE pins of each module for
multiple module operations.
4. Place the modules evenly on the board and leave enough
space between modules. If the board space is limited, try to
put the modules with low power loss closely together (i.e. low
In current sharing mode, the phase-shift is needed to interleave
the different phases to lower the input and output ripples. As
shown in Table 2, there are different sharing modes from
2-phase (180° phase-shift) and 4-phase (90° phase-shift) to
6-phase (60° phase-shift). The master module sends the CLKOUT
signal to the SYNC pin of the second module with the phase-shift
to its own clock signal. Then the second module synchronizes to
the CLKOUT signal of the master module and sends its CLKOUT
signal to the third module’s SYNC pin. The individual 2 phases of
each module are set to be 180° phase-shift by default. This
evaluation board is set to mode 5B with 60° phase-shift between
phases.
VOUT or IOUT) while still separating the module with high power
loss.
5. If the ambient temperature is high or the board space is
limited, airflow is needed to dissipate more heat from the
modules. A heat sink can also be applied to the top side of the
module to further improve the thermal performance (heat
sink recommendation: Aavid Thermalloy, part number
375424B00034G, www.aavid.com).
If the MODE pin is not tied to VCC (5A or 5B), all VMON pins of
different modules can be tied together, except the VMON pin of
the master phase. If mode 7A is needed to allow for 90°
phase-shift, the MODE pin has to tie to VCC. In this case, the
VMON pin of the associated module needs to be separated by
connecting a 1.05kΩ resistor to SGND, as shown in the
ISL8225M datasheet.
Remote Sensing
The ISL8225MEVAL2Z board allows the user to apply the remote
sensing function to loads in order to achieve good output
regulation accuracy. To make use of this function, remove
resistors R7 and R8 and connect the kelvin sensing lines through
the jumper JP4 (RS) to the point of load.
TABLE 2. ISL8225M 3-MODULE BOARD OPERATION MODES
1ST MODULE (I = INPUT; O = OUTPUT; I/O = INPUT AND OUTPUT, BI-DIRECTION)
MODES OF OPERATION
ISHARE (I/O)
REPRESENTS
WHICH
OPERATION OPERATION
MODE
OF 2ND
MODULE
MODE
OF 3RD
MODULE
EN2 EN3 VSEN2- MODE VSEN2+ CLKOUT/REFIN CHANNEL(S) 2ND CHANNELWRT
MODE
5A
(I)
(I)
(I)
(I)
(I)
WRT 1ST (I OR O)
CURRENT
1ST (O)
180°
180°
180°
OUTPUT
2-Phase
6-Phase
4-Phase
12-Phase
0
0
VCC
VCC
VCC
GND
GND
VCC
-
-
60°
60°
90°
Both Channels
Both Channels
Both Channels
-
-
5B
-
5B
1
1
5B
7A
1
0
VCC
5A or 7A
8
Cascaded Module Operation MODEs 5A+5A+7A+5A+5A+5A/7A, No External Clock Required
AN1789.0
December 3, 2012
3
INTERSIL [ Intersil ]
