NR263S Datasheet, PDF (19/29 Pages) Sanken electric – Light Load High Efficiency Synchronous Buck Regulator IC

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 ΔI_L / Io ratio
When the ΔI_L/Io ratio is increased, the Inductance decreases.However, there is a matter of trade-off, for example, the
output ripple voltage increases.When the ΔI_L/Io ratio is decreased, required inductance increases, and the outer
shape of the Inductor becomes larger. Setting of the ΔI_L/Io ratio to 0.2 or 0.3 is conventionally regarded as a setting
for good cost performance.
 Diameter of the wire winding
When the Inductance is increased, if the core-size of the Inductor is identical, the number of turns of windings will
increase, and the diameter of wire windings will be thinner. Because the DC resistance DCR also increases, the large
current can't to flow. If the DCR is in priority, the core size of the Inductor enlarges.
 DC superposition characteristics
Depending on the material or shape of the core, the inductance of inductor has DC superposition characteristics that
decreases gradually by the flowing DC current. Be sure to confirm if the inductance value is significantly lower than
the design value when making the maximum load current for practical use flow. Obtain the data of the DC
superposition characteristics including graphs from the manufacturer of the coil to understand the characteristics of
the Inductor used in advance. In doing so, important parameters are:
1) Saturation point...At what ampere does magnetic saturation occur?
2) Inductance fluctuation with the practical load current
For example, for using it up to 1 A in the actual load Io, it can not use the Inductor which the saturation point is such
as 0.5 A. In addition, in spite of having an inductance of 10 μH at the no-load, please pay caution for the thing
which has the characteristic that it decreases to such as 5μH by the superposition current of 1A.
 Less noise
If the core is the open magnetic circuit type shaped like a drum, the magnetic flux passes outside the Inductor, so
that the peripheral circuit might be damaged due to noise. Use the Inductor which has a core/structure of the
low-leakage magnetic flux type. For details, consult the manufacturer of the Inductor.
 Heat generation
In actuality, when using the coil for mounting the PCB, heat generation of the coil main body might be influenced
by peripheral parts. In most cases, temperature rise of the coil includes the Inductor’s own heat generation, and there
are temperature limitations such as below:
1) onboard(Cars) grade product: 150°C
2) highly-reliable product: 125°C
3) general product: 85-100°C
Be sure to evaluate heat generation because temperature rise differs when the PCB on which the Inductor is mounted
is designed differently.In general, Inductors with a smaller DCR value on the specification sheet have smaller loss.
* Select the most appropriate one in consideration of the conditions of use, mounting, heat dissipation, etc.
NR263S series-DSE Rev.1.0
SANKEN ELECTRIC CO.,LTD
19
2016.03.09
http://www.sanken-ele.co.jp/en/
© SANKEN ELECTRIC CO.,LTD. 2016