User Guide 071
UG071.0
May 3, 2016
4
PWM/PFM Selection
By default, ISL8202MEVAL1Z is set to operate in PWM mode.
This is achieved by connecting SYNC to VIN through R
1
. Pulling
the SYNC pin LOW, forces the module into PFM mode, which
enables pulse-skipping at light load to minimize the switching
loss by reducing the switching frequency. Refer to
datasheet for more detailed information. For ISL8202MEVAL1Z,
PFM mode can be enabled by removing R
1
and shorting SYNC to
SGND by putting a 0
Ω
resistor on R
2
.
Soft Start-Up
The soft start-up reduces the inrush current during the start up.
For ISL8202MEVAL1Z, the soft start-up time is set to 1ms by
default through C
6
. However, start-up time can be adjusted by
tuning the C
6
can be used to determine the C
6
value for the target soft-start time t
SS
.
Evaluation Board Information
The ISL8202MEVAL1Z evaluation board is a 2x2 in
2
four-layer FR-4
board with 2oz. copper on all the layers. The board can be used as a
single 3A reference design. Refer to
for board
layout information. The board is designed with mechanical switches
for ENABLE, power-good LED indicators, several connectors, test
points and jumpers, which make testing the board easy.
Thermal Considerations and
Current Derating
Board layout is very critical in order to make the module operate
safely and deliver maximum allowable power. In order for the board
to operate properly in the high ambient temperature environments
and carry full load currents, the board layout needs to be carefully
designed to maximize thermal performance. To achieve this, select
enough trace width, copper weight and proper connectors.
The ISL8202MEVAL1Z evaluation board is capable of operating at
3A full load current at room temperature with plenty of safety
margin for junction temperature. However, if the board is to operate
at elevated ambient temperatures, then the available output current
may need to be derated. Refer to the derated current curves in the
datasheet to determine the maximum output current
the evaluation board can supply.
FIGURE 6. OPERATION REGION V
IN
= 5.0V
FIGURE 7. OPERATION REGION V
IN
= 4.0V
FIGURE 8. OPERATION REGION V
IN
= 3.3V
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.6
1
1.4
1.8
2.2
2.6
3
3.4
3.8
4.2
OUTPUT VOLTAGE (V)
SWIT
CHING FR
E
QUENCY (MHz)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.6
1
1.4
1.8
2.2
2.6
3
3.4
OUTPUT VOLTAGE (V)
S
W
ITCHIN
G
FREQUENCY (MHz)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.6 0.8
1
1.2 1.4 1.6 1.8
2
2.2 2.4 2.6 2.8
OUTPUT VOLTAGE (V)
SWITCHING FREQUENCY (MHz
)
FIGURE 9. OPERATION REGION V
IN
= 2.6V
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.6
0.8
1
1.2
1.4
1.6
1.8
2
OUTPUT VOLTAGE (V)
SWITCHING FREQUENCY (MHz
)
C
6
F
3.1 t
SS
S
=
(EQ. 3)
