FAN5307MP15X FAIRCHILD [Fairchild Semiconductor], FAN5307MP15X Datasheet - Page 9

• Manufacturer Part Number: FAN5307MP15X
• Description: High-Efficiency Step-Down DC-DC Converter
• Manufacturer: FAIRCHILD [Fairchild Semiconductor]

FAN5307 Rev. 1.0.4
Application Information
Adjustable Output Voltage Version
The output voltage for the adjustable version is set by the
external resistor divider, as shown below:
and is calculated as:
To reduce noise sensitivity, R1 + R2 should not exceed
1M .
Inductor Selection
The inductor parameters directly related to device perfor-
mances are saturation current and dc resistance. The
FAN5307 operates with a typical inductor value of 10µH.
The lower the dc resistance, the higher the efficiency.
For saturation current, the inductor should be rated
higher than the maximum load current plus half of the
inductor ripple current that is calculated as follows:
where:
f = Switching Frequency
L = Inductor Value
V
I
Inductor
OUT
I
L
L
Value
6.8µH
= Inductor Ripple Current
10µH
10µH
=
=
V
Table 1: Recommended Inductors
OUT
0.5V
Vendor
Sumida
Sumida
Murata
Murata
1
----------------------------------------- -
–
1
+
V
L f
OUT
R
------ -
R
1
2
LQH66SN100M01L
CDRH3D16-6R8
CDRH5D28-100
CDRH5D18-100
CDRH4D28-100
CDRH4D18-100
LQH4C100K04
V
Part Number
IN
CR32-100
CR43-100
100k
Efficiency
Smallest
Solution
Perfor-
mance
High
9
Input Capacitor Selection
For best performances, a low ESR input capacitor is
required. A ceramic capacitor of at least 4.7µF, placed as
close to the input pin of the device is recommended.
Output Capacitor Selection
The FAN5307’s switching frequency of 1MHz allows the
use of a low ESR ceramic capacitor with a value of 10µF
to 22µF. This provides low output voltage ripple. In power
save mode the output voltage ripple is independent of
the output capacitor value and the ripple is determined
by the internal comparator thresholds. The typical output
voltage ripple at light load is 1% of the nominal output
voltage.
PCB Layout Recommendations
T
quency of the power supplies require a careful PCB lay-
out design. Therefore, use wide traces for the high
current path and place the input capacitor, the inductor,
and the output capacitor as close as possible to the inte-
grated circuit terminals. For the adjustable version the
resistor divider should be routed away from the inductor
to avoid electromagnetic interference.
The 6-lead MLP version of the FAN5307 separates the
high current ground from the reference ground, therefore
it is more tolerant to the PCB layout design and shows
better performance.
he inherently high peak currents and switching fre-
Capacitor
Value
4.7µF
10µF
22µF
Table 2: Recommended Capacitors
Taiyo Yuden
Vendor
Murata
TDK
C12012X5ROJ106K
GRM32DR60J226K
C3216X5ROJ106M
JMK212BY475MG
JMK212BJ106MG
JMK316BJ106KL
Part Number
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