Ricoh RV5VH - Manual (Page 51)

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RV5VH3
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APPLICATION HINTS
When using these ICs, be sure to take care of the following points.
• Set external components as close as possible to the IC and minimize the connection between the
components and the IC. In particular, when an external component is connected to VOUT Pin, make
minimum connection with the capacitor.
• Make sufficient grounding. A large current flows through GND Pin byswitching. When the impedance of
the GND connection is high, the potential within the IC is varied by switching current. This may result in
unstableoperation of the IC.
• Use capacitor with good high frequency characteristics such as tantalum capacitor, aluminium electrolytic
capacitor and ceramic capacitor. We recommend the use of a capacitor with an allowable voltage which is
at least three times the output set voltage. This is because there may be the case where a spike-shaped
high voltage is generated by the inductor when Lx transistor is turned OFF.
• Take the utmost care when choosing an inductor. Namely, choose such an inductor that has sufficiently
small d.c. resistance and large allowable current, and hardly reaches magnetic saturation. When the
inductance value of the inductor is small, there may be the case where ILX exceeds the absolute maximum
ratings at the maximum load. Use an inductor with an appropriate inductance. (See OUTPUT CURRENT
and SELECTION OF PERIPHERAL COMPONENTS sections.)
• Use a diode of a Schottky type with high switching speed, and also take care of the rated current. (See
OUTPUT CURRENT and SELECTION OF PERIPHERAL COMPONENTS sections.)
The performance of power source circuits using these ICs largely depends upon the peripheral circuits. Take
the utmost care in the selection of the peripheral circuits. In particular, design the peripheral circuits in such
a manner that the values such as voltage, current and power of each component, PCB patterns and the IC do
not exceed their respective rated values.