ame5249-aevadjl AME, Inc., ame5249-aevadjl Datasheet - Page 12

• Manufacturer Part Number: ame5249-aevadjl
• Description: Synchronous Buck Converter
• Manufacturer: AME, Inc.

Output Capacitor Selection
series resistance (ESR). Typically, once the ESR re-
quirement for C
generally far exceeds the I
output ripple V
tance and
output voltage, the output ripple is highest at maximum
input voltage since
Saving Mode, and the output voltage ripple is indepen-
dent of the value of the output capacitor. The output ripple
is set by the internal comparator thresholds and is also
affected by the feedback capacitor C1 in figure2. Large
capacitor values can decrease the output ripple, usually
a 22pF capacitor is sufficient for most applications.
sen, choose the X5R or X7R dielectric formulations. These
dielectrics have the best temperature and voltage char-
acters have the best temperature and voltage character-
istics of all the ceramics for a given value and size.
resistor divider according to following formula:
The external resistor divider is connected to the output.
12
AME5249
V
Output Voltage Setting
OUT
The selection of C
V
At the light load current, the device operates in Power
When the input and output ceramic capacitors are cho-
In the adjustable version, the output voltage is set by a
Where f
OUT
0
6 .
△
SW
V
I
I
L
=operating frequency, C
L
=ripple current in the inductor. For a fixed
(
OUT
AME
OUT
ESR
1 (
is determined by
has been met, the RMS current rating
△
OUT
R
R
I
2
1
L
8
is driven by the required effective
)
increases with input voltage.
C
OUT
RIPPLE
1
f
SW
(P-P) requirement. The
)
OUT
=output capaci-
Thermal Considerations
much heat due to its high efficiency. But, in applications
where the AME5249 is running at high ambient tempera-
ture with low supply voltage and high duty cycles, such
as in dropout, the heat dissipated may exceed the maxi-
mum junction temperature of the part. If the junction tem-
perat ure reac hes approximat ely 160
switches will be turned off and the SW node will become
high impedance. To avoid the AME5249 from exceeding
the maximum junction temperature, the user will need to
do some thermal analysis. The goal of the thermal analy-
sis is to determine whether the power dissipated exceeds
the maximum junction temperature of the part. The tem-
perature rise is given by:
to the ambient temperature.
J
In most applications the AME5249 does not dissipate
Where PD is the power dissipated by the regulator and
A
TR
is the thermal resistance from the junction of the die
Synchronous Buck Converter
(
PD
)
JA
1.5MHz, 600mA
℃
, bot h power
Rev.A.01