AS1341(2007) データシートの表示（PDF） - austriamicrosystems AG
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AS1341 Datasheet PDF : 16 Pages
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AS1341
Data Sheet - Application Information
Diode Selection
The current in the D1 (see Figure 22 on page 10) changes abruptly from zero to its peak value each time the LX switch
turns off. To avoid excessive losses, the diode must have a fast turn-on time and a low forward voltage.
Note: Ensure that the diode peak current rating exceeds the peak current limit set by the current limit (see Setting
Current Limit on page 10), and that its breakdown voltage exceeds VIN. Schottky diodes are recommended.
Stable Operation
A well-designed system and selection of high-quality external components can eliminate excessive noise on pins OUT,
FB, or GND, which can lead to unstable device operation. Instability typically manifests itself as grouped switching
pulses with large gaps and excessive low-frequency output ripple (motorboating) during no-load or light-load condi-
tions.
Recommended Components
Table 8. Recommended Components
Circuit
Input
Voltage (V)
Output
Voltage (V)
1
4.5 to 20
1.25 to 5
2
4.5 to 12
ILIMIT
High
3
4.5 to 20
1.25 to 5
Low
4
4.5 to 12
5
6 to 20
5 to VIN
High or Low
Inductor
MSS6132-103ML
LQH66SN-100M03
LQH55DN-150M03
CDRH6D28NP-150
CDRH5D18NP-4R1
LPS4018-472ML
MSS6132-393ML
CDRH6D28NP-470
LQH66SN-470M03
LQH55DN-470M03
MSS6132-103ML
LPS4018-223ML
CDRH5D18NP-220
See Circuit 1-4
Output Capacitor
T520V107M010ATE018
A700V826M006ATE018
T520B107M006ATE040
EEFUD0J101R
10TPB100ML
EEFCD0K330R
6TPB47M
T520A336M006ATE070
A700V226M006ATE028
510X107M020ATE040
PC Board Layout and Grounding
High switching frequencies and large peak currents make PC board layout an important part of AS1341-based
designs. Good PCB layout can avoid switching noise being introduced into the feedback path, resulting in jitter, insta-
bility, or degraded performance.
- High-power traces (see Figure 22 on page 10) should be as short and wide as possible.
- The current loops formed by the external components (CIN, COUT, L1, and D1 see Figure 22 on page 10) should
be as short as possible to avoid radiated noise. Connect the ground pins of these power components at a com-
mon node in a star-ground configuration.
- Separate noisy traces, such as the LX node, from the feedback network with grounded copper.
- Keep the extra copper on the PCB and integrate it into a pseudo-ground plane.
- When using external feedback, place the resistors as close to pin FB as possible to minimize noise coupling.
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