AS1324-BTTT-12 データシートの表示（PDF） - austriamicrosystems AG
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AS1324-BTTT-12 Datasheet PDF : 20 Pages
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AS1324
Data Sheet - Application Information
For best overall efficiency use an inductor with a rating of 720mA or greater and less than 0.2Ω series resistance. CIN
will require an RMS current rating of at least 0.3A ≅ ILOAD(MAX)/2, whereas COUT will require an ESR of less than
0.25Ω. In most cases, a ceramic capacitor will satisfy this requirement.
For the feedback resistors, select the value for R1 = 375kΩ. R2 can then be calculated from (EQ 7) to be:
R2 = (VOUT/0.6 - 1)375k = 1000kΩ
Layout Considerations
The AS1324 requires proper layout and design techniques for optimum performance.
! The power traces (GND, SW, and VIN) should be kept as short, direct, and wide as is practical.
! Pin VFB (AS1324 only) should be connected directly to the feedback resistors (R1 and R2). A potentiometer as
replacement for R1 and R2 should be avoided to minimize the output voltage ripple and to maintain the stability of
the regulator.
! The resistive divider (R1/R2) must be connected between the positive plate of COUT and ground.
! The positive plate of CIN should be connected as close to VIN as is practical since CIN provides the AC current to
the internal power MOSFETs.
! Switching node SW should be kept far away from the sensitive VFB node.
! The negative plates of CIN and COUT should be kept as close to each other as is practical. A starpoint to Ground is
recommended.
Figure 29. AS1324 Basic PCB Layout
R1
VIN
Via to VIN
VOUT
1
5
L1
2 AS1324
SW 3
4
R2
CFWD
COUT
CIN
GND
Via to GND
Via to VOUT
Figure 30. AS1324 Basic Diagram
VOUT
1
EN
2
GND
COUT
3
L1 SW
5
VFB
AS1324
4
VIN
CIN
R2
CFWD
High Current Path
R1
VIN
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Revision 1.03
16 - 20
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