Application Note 1789
ISL8225MEVAL2Z 6-Phase, 90A Evaluation Board Setup
Procedure
The ISL8225M is a complete, dual step-down switching mode
DC/DC module. The dual outputs can easily be paralleled for
single-output, high-current use. It is easy to apply this
high-power, current-sharing DC/DC power module to
power-hungry datacom, telecom, and FPGA applications. All
that is needed in order to have a complete, dual 15A design
ready for use are the ISL8225M, a few passive components,
and V
OUT
setting resistors.
The ease of use virtually eliminates design and manufacturing
risks while dramatically improving time to market. Need more
output current? Simply parallel up to six ISL8225M modules to
scale up to an 180A solution.
The ISL8225M has a thermally enhanced, compact QFN
package that operates at full load and over-temperature
without requiring forced-air cooling. Easy access to all pins,
with few external components, reduces PCB design to a
component layer and a simple ground layer.
The ISL8225MEVAL2Z evaluation board allows for a single
6-phase paralleled output, which delivers high current up to
90A. The input voltage is 4.5V to 20V and the default output
voltage on this board is set at 1.2V. The current level for this
board is 90A with no extra cooling required.
Recommended Equipment
• 0V to 20V power supply with at least 10A source current
capability
• Electronic load capable of sinking current up to 90A
(multiple electronic current loads can be used in parallel to
sink more current)
• Digital multimeters (DMMs)
• 100MHz quad-trace oscilloscope
Quick Start
The inputs are J3 (VIN) and J4 (GND). The outputs are J1 and
J5 (VOUT), J2 and J6 (GND) and J6 (VOUT2). Please refer to
Figure 1. This 90A evaluation board can be easily modified to
30A (one module) or 60A (two modules) operation.
1. Connect a power supply capable of sourcing at least 10A to
the input (VIN J3 & GND J4) of the ISL8225MEVAL2Z
evaluation board, with a voltage between 4.5V to 20V.
Connect an electronic load or the device to be powered to
the output (VOUT (J1, J5) & GND (J2, J6)) of the board. All
connections, especially the low voltage, high current V
OUT
lines, should be able to carry the desired load current and
should be made as short as possible. Duplicated tab
connections on VOUT (J1, J5) and GND (J2, J6) to carry large
current.
2. Ensure the jumpers for EN2 and EN3 are in the “ON”
position and EN is open. Turn on the power supply. If the
board is working properly, the green LED will illuminate; if
not, the red LED will illuminate (recheck the wire/jumper
connections in this case). Measure the output voltage, V
OUT
,
which should be at 1.2V.
3. The ISL8225MEVAL2Z is manufactured with a V
OUT
default
value of 1.2V; if different output voltages are desired, board
resistors can be exchanged to provide the desired V
OUT
. Please
refer to Table 1 on page 2 for R2/R64 resistor values, which
can be used to produce different output voltages.
Related Resources
See how-to
video at
intersil.com/
evid02
+
V
IN
-
V
4.5V TO 20V
+
-
LOAD
(0A~90A)
NOTE 1
+
V
-
V
OUT
NOTE:
1. Multiple loads can be paralleled to
reach 90A (i.e. Two 45A loads
paralleled together).
FIGURE 1. ISL8225MEVAL2Z BOARD IMAGE
December 3, 2012
AN1789.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Copyright Intersil Americas Inc. 2012. All Rights Reserved.
1-888-INTERSIL or 1-888-468-3774
|
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Application Note 1789
For 12V V
IN
and V
OUT
more than 1.5V, the switching frequency
will need to be adjusted, as shown in Table 1. The resistor R
FSET
can be adjusted for the desired frequency. No frequency
adjustments are necessary for V
OUT
below 1.5V. For 5V V
IN
, the
frequency does not need to be adjusted and the module default
frequency can be used at any allowed V
OUT
. If the output voltage
is set to more than 1.8V, the output current will need to be
derated to allow for safe operation. Please refer to the derating
curves in the
ISL8225M datasheet.
TABLE 1. VALUE OF BOTTOM RESISTOR FOR DIFFERENT OUTPUT
VOLTAGES (R1 = 1k)
V
OUT
(V)
0.6
0.8
1.0
1.2
1.5
2.5
3.3
5.0
5.5
R2 /R64
(Ω)
0/0
3010/1500
1500750
1000/500
665/332
316/158
221/110
137/68.1
121/60.4
FREQUENCY
(kHz)
Default
Default
Default
Default
Default
650
800
950
950
R
FSET
(Ω)
(V
IN
= 12V)
Default
Default
Default
Default
Default
249k
124k
82.5k
82.5k
Evaluation Board Information
The evaluation board size is 150mm x 130mm. It is a 6-layer
board, containing 2-ounce copper on the top and bottom layers
and 1-ounce copper on all internal layers. The board can be used
as a 90A reference design. Refer to the “Layout” section
beginning on page 7. The board is made of FR4 material and all
components, including the solder attachment, are lead-free.
Current Sharing Check
The evaluation board allows the user to measure the current
sharing accuracy. Four zero ohm resistors (i.e. R59~R62 for M1
channel 2 in Figure 2) are put serially on each output with two on
each side of the evaluation board. To measure the output current
of each phase, please remove all four resistors and put looped
wires or sensing resistors on correct positions.
Although the assembled resistors have zero resistance, there is
still small resistance (< 50mΩ) on each resistor. At large output
current, the efficiency can be decreased by 1~3% due to the
power loss on those zero ohm resistors. The efficiency curves are
shown in Figures 16 and 17 with zero ohm resistors, while
Figures 18 and 19 show the efficiency curves by replacing those
resistors with short copper straps.
Thermal Considerations and Current Derating
For high current applications, board layout is very critical in order
to make the module operate safely and deliver maximum
allowable power. To carry large currents, the board layout needs
to be designed carefully to maximize thermal performance. To
achieve this, select enough trace width, copper weight and the
proper connectors.
This evaluation board is designed for running 90A @ 1.2V at
room temperature without additional cooling systems needed.
However, if the output voltage is increased or the board is
operated at elevated temperatures, then the available current is
derated. Refer to the derated current curves in the
datasheet
to
determine the output current available.
For layout of designs using the ISL8225M, the thermal
performance can be improved by adhering to the following
design tips:
1. Use the top and bottom layers to carry the large current.
VOUT1, VOUT2, Phase 1, Phase 2, PGND, VIN1 and VIN2
should have large, solid planes. Place enough thermal vias to
connect the power planes in different layers under and
around the module.
2. Phase 1 and Phase 2 pads are switching nodes that generate
switching noise. Keep these pads under the module. For
noise-sensitive applications, it is recommended to keep
phase pads only on the top and inner layers of the PCB; do not
place phase pads exposed to the outside on the bottom layer
of the PCB. To improve the thermal performance, the phase
pads can be extended in the inner layer, as shown in Phase 1
and 2 pads on layer 3 (Figure 11) for this 90A evaluation
board. Make sure that layer 2 and layer 4 have the GND layers
to cover the extended areas of phase pads at layer 3 to avoid
noise coupling.
Board Setting
If low current applications are needed, this 90A evaluation board
can be easily programmed to 30A and 60A use.
30A Application (1 Module)
EN -- Open, EN2-- OFF, EN3 -- OFF
In this mode, only module 1 is running and modules 2 and 3 are
disabled.
60A Application (2 Modules)
EN -- Open, EN2-- ON, EN3 -- OFF
Or:
EN -- Open, EN2-- OFF, EN3 -- ON
In this mode, only modules 1 and 2 (or 3) are running and
module 3 (or 2) is disabled.
90A Application (3 Modules)
EN -- Open, EN2-- ON, EN3 -- ON
In this mode, all modules are running.
Disable All Modules and Use the EN Pin to
Start the Modules
EN -- Connected
In this mode, all modules are disabled and EN can be used to
control all modules to startup.
2
AN1789.0
December 3, 2012
Application Note 1789
3. To avoid noise coupling, we recommend adding 1nF
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
V
OUT
or I
OUT
) 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).
Phase-shift Programming
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.
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
1
ST
MODULE (I = INPUT; O = OUTPUT; I/O = INPUT AND OUTPUT, BI-DIRECTION)
MODES OF OPERATION
OPERATION
MODE
OF 3
RD
MODULE
-
5B
-
MODE
5A
5B
7A
8
EN2
(I)
0
1
1
EN3
(I)
0
1
0
VSEN2-
(I)
V
CC
V
CC
V
CC
MODE
(I)
GND
GND
V
CC
ISHARE (I/O)
OPERATION
REPRESENTS
MODE
WHICH
OF 2
ND
VSEN2+ CLKOUT/REFIN CHANNEL(S) 2
ND
CHANNEL WRT
CURRENT
(I)
WRT 1
ST
(I OR O)
1
ST
(O)
MODULE
-
-
V
CC
60°
60°
90°
Both Channels
Both Channels
Both Channels
180°
180°
180°
-
5B
5A or 7A
OUTPUT
2-Phase
6-Phase
4-Phase
12-Phase
Cascaded Module Operation MODEs 5A+5A+7A+5A+5A+5A/7A, No External Clock Required
3
AN1789.0
December 3, 2012
ISL8225MEVAL2Z Board Schematics
SYNC
TP5
SYNC
IN
RFSET
100PF
R14
SYNC
OUT
IN
R22
OPEN
249K
4.5V TO 20V
VIN
J3
VIN
OUT
OPEN
C18
VCC1
TP7
C32
DNP
C7
0
VMON
OUT
IN
TP1
VOUT
1.2V @ 90A
C8
1000PF
J1
TP3
TP6
S1
E
C1
4.7UF
S1
MODE1
OUT
R64
S1
R82
499
VOUT
IN
499
S1
OUT
E
VOUT
J5
VIN
R42
1000PF
0
C19
COMP
R62
R59
0
0
470UF
CINB
CINA
CIN1
CIN3
22UF
22UF
R61
330UF
47UF
C05
470UF
CIN2
S1
22UF
R60
0
0
C08
CIN4
22UF
C07
PHASE2U1
VSEN2-
VSEN2+
J4
GND
E
10
26
25
TP4
11
N/C
M1
ISL8225MIRZ
V1SEN2+
TP8
IN
0
PGOOD
24
23
OUT
PGOOD
12
47UF
C02
IN
DNP
IN
VSEN1+
VSEN1-
OPEN
R47
21
R5
3K
R1
1000PF
DNP
R10
R7
C01
+
0
0
R10B
S1
VCC1
IN
R2
1K
RS
-
C40
R8
0
OPEN
C03
JP4
PGND
VIN1
1K
OPEN
0
DNP
22
C04
0
C08A
330UF
VCC1
R15
MODE1
PHASE1U1
C12
VCC1
IN
R16
R56
DNP
DNP
V1SEN2+
IN
E
1000PF
C11
COMP
OUT
C35
0.01UF
R9
1000PF
0
S1
S1
R18
JP8
IN
R6
R12
3.32K
3.32K
1
3
C29
VCC1
OUT
1000PF
R11
EN/FF
0
C4
ISHARE
SGND1
S1
E
E
OUT
EN
S3
1K
S1
R13
100PF
VMON
IN
OPEN
C10
SSL_LXA3025IGC
2
3
4
LED1
C5
S3
1000PF
CLKOUT1
OUT
C6
DNP
S1
DRAWN BY:
RELEASED BY:
UPDATED BY:
TIM KLEMANN
S1
S1
PGOOD
IN
1
Q1
2N7002-7-F
2
E
TIM KLEMANN
S1
FIGURE 2. ISL8225MEVAL2Z BOARD SCHEMATIC
AN1789.0
December 3, 2012
IN
GND
1
R9B
VCC1
OPEN
VIN2
OPEN
C06
4
VOUT
IN
9
8
7
6
5
4
3
2
E
COMP2
SGND
VCC
MODE
SYNC
VMON2
PGND
VOUT
TP9
PHASE2
PHASE1
13
14
R40
R38
0
0
VOUT2
GND
E
E
Application Note 1789
R53
0
TP10
VOUT1
R39
CLKOUT
ISHARE
VMON1
COMP1
EN/FF2
EN/FF1
J2
20
15
16
17
18
19
GND
GND_S1
EGND
J6
RED
GRN
DATE:
DATE:
DATE:
08/23/2012
ENGINEER:
TITLE:
JIAN YIN
DATE:
11/01/2012
TESTER
MASK#
ISL8225M
EVALUATION BOARD
SCHEMATIC
HRDWR ID
ISL8225MEVAL2Z
SHEET
REV.
D
FILENAME:
ISL8225MEVAL2Z Board Schematics
(Continued)
100PF
CLKOUT1
VCC2
OUT
R54
R28
OPEN
R25
R23
C33
C14
DNP
DNP
0
R35
0
VMON
IN
0
OUT
C2
4.7UF
S2
E
MODE2
OUT
VMON1
OUT
R43
1000PF
0
S2
R45
0
C26
VIN
IN
COMP2
OUT
OUT
COMP
R67
0
R71
0
CIN5
22UF
CIN7
22UF
CIN6
22UF
CIN8
S2
22UF
0
SGND
COMP2
VCC
MODE
SYNC
VMON2
R72
0
PGND
VIN2
C012
PHASE2U2
VSEN2-
10
E
M2
ISL8225MIRZ
VSEN2+
26
25
V2SEN2+
PGOOD
IN
0
VCC2
R65
0
OPEN
OPEN
VCC2
IN
R48
DNP
MODE2
IN
11
N/C
PGOOD
24
23
OUT
12
PHASE1U2
R49
VSEN1+
VSEN1-
22
21
C37
OPEN
0
C010
OPEN
OPEN
R20
0
C36
DNP
PGND
VIN1
R20B
S2
R4
DNP
R86
DNP
OPEN
C42
C011
47UF
47UF
C09
VCC2
IN
R17
DNP
V2SEN2+
IN
VCC2
IN
S2
R3
DNP
R87
DNP
R57
DNP
EN/FF
EN2
3
2
1
C25
OUT
1000PF
E
COMP2
OUT
C47
OPEN
S2
ON
E
C16
R19
S2
S2
0
IN
C30
R27
100PF
VMON1
1000PF
GND_S2
S2
EGND
C17
S2
OPEN
C15
SGND2
E
CLKOUT2
OUT
C13
1000PF
OFF
0
1000PF
J8
S2
R52
0
OUT
ISHARE
S2
DRAWN BY:
S2
RELEASED BY:
UPDATED BY:
TIM KLEMANN
DATE:
DATE:
DATE:
08/23/2012
ENGINEER:
TITLE:
OPEN
C0
TIM KLEMANN
S2
FIGURE 3. ISL8225MEVAL2Z BOARD SCHEMATIC
IN
1
C015
R28B
330UF
C013
C016
47UF
5
AN1789.0
December 3, 2012
E
R68
9
PHASE2
PHASE1
13
8
14
7
EN/FF1
6
EN/FF2
5
CLKOUT
4
VMON1
3
ISHARE
2
VOUT2
Application Note 1789
R69
0
E
R66
0
VOUT
OUT
VOUT1
COMP1
R70
0
20
15
16
17
18
19
JIAN YIN
DATE:
11/01/2012
TESTER
MASK#
ISL8225M
EVALUATION BOARD
SCHEMATIC
HRDWR ID
REV
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