AS3645 austriamicrosystems, AS3645 Datasheet - Page 28

• Manufacturer Part Number: AS3645
• Description: 1000/720ma Ultra Small High Efficient Single/dual Led Flash Driver With Safety Features
• Manufacturer: austriamicrosystems

AS3645
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
If a different input capacitor is chosen, ensure similar ESR value and at least 4µF capacitance at the maximum input
supply voltage. Larger capacitor values (C) may be used without limitations.
Output Capacitor C
Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since
they have extremely low ESR and are available in small footprints. The capacitor should be located as close to the
device as is practical.
X5R dielectric material is recommended due to their ability to maintain capacitance over wide voltage and temperature
range.
Table 17. Recommended Output Capacitor
If a different output capacitor is chosen, ensure similar ESR values and at least 4µF capacitance at 10V output voltage.
Inductor L
The fast switching frequency (2MHz) of the AS3645 allows for the use of small SMDs for the external inductor. The
saturation current I
low DC resistance (DCR) to reduce the I
Table 18. Recommended Inductor
If a different inductor is chosen, ensure similar DCR values and at least 1.5µH inductance at I
PCB Layout Guideline
The high speed operation requires proper layout for optimum performance. Route the power traces first and try to min-
imize the area and wire length of the two high frequency/high current loops:
Loop1: C
Loop2: C
At the pin PGND a single via (or more vias, which are closely combined) connects to the common ground plane. This
via(s) will isolate the DCDC high frequency currents from the common ground (as most high frequency current will flow
between Loop1 and Loop2 and will not pass the ground plane) - see the ‘island’ in
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GRM219R61A116U
14.Can be adjusted in I
FDSE0312-2R2M
ELL3FU2R2NBN
Part Number
Part Number
VIN
VIN
DCDC
- L
- L
DCDC
DCDC
SATURATION
- pin SW - pin PGND - C
- pin SW - pin VOUT - C
VOUT
2
>1.54µH @ 1.9A
>1.54µH @ 2.3A
C mode with register
should be chosen to be above the maximum value of I
10µF +/-10%
>4.2µF@5V
>4µF@10V
2.2µH
2.2µH
C
L
2
R power losses - high DCR values will reduce efficiency.
VOUT
VIN
TC Code
max. 160m Ω
max. 160m Ω
typ. 120m Ω
typ. 140m Ω
coil_peak (see page 23)
X5R
- pin PGND - C
DCR
Revision 1.6
30m Ω
ESR
I
SATURATION
VIN
1.8A
2.3A
Voltage
Rated
10V
3x3x1.1mm
max 1.2mm
3x3x1.1mm
max 1.2mm
height
height
Size
Figure
0805
Size
LIMIT
14
30.
. The inductor should have
LIMIT
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Manufacturer
Manufacturer
www.toko.com
.
Panasonic
Murata
Toko
28 - 33