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.
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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.
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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.
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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
R2
Via to GND
Via to VOUT
1
5
AS1324
4
2
3
VOUT
L1
CFWD
SW
COUT
CIN
GND
Figure 30. AS1324 Basic Diagram
High Current Path
1
5
EN
VFB
AS1324
2
R2
R1
GND
COUT
CFWD
VOUT
3
4
L1
VIN
SW
CIN
VIN
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