FAN5350 データシートの表示（PDF） - ON Semiconductor
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FAN5350 Datasheet PDF : 15 Pages
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PCB Layout Guidelines
For the bill of materials of the FAN5350 evaluation board,
see Table 1. There are only three external components:
the inductor and the input and output capacitors. For any
buck sw itcher IC, including the FAN5350, it is alw ays
important to place a low -ESR input capacitor very close to
the IC, as show n in Figure 7. That ensures good input
decoupling, w hich helps reduce the noise appearing at
the output terminals and ensures that the control sections
of the IC do not behave erratically due to excessive noise.
This reduces sw itching cycle jitter and ensures good
overall performance. It is not considered critical to place
either the inductor or the output capacitor very close to
the IC. There is some flexibility in moving these tw o
components further aw ay from the IC.
Table 2. FAN5350 Evaluation Board Bill of Materials (optional parts are installed by request only)
Description
Qty.
1.2µH, 1.8A, 55mΩ
Inductor
1.3µH, 1.2A, 90mΩ 1
1.5µH, 1.3A
Capacitor 4.7µF, ±10%, 6.3V, X5R, 0603
2
IC DC/DC Regulator in CSP, 5 bumps
1
Load Resistor (Optional)
1
Figure 7. The FAN5350 Evaluation Board PCB (CSP)
Ref.
Vendor
Part Number
TOKO
1117AS-1R2M
L1
FDK
MIPSA2520D1R0
Taiyo Yuden
CBC3225T15MR
CIN,COUT
U1
MURATA
GRM39 X5R 475K 6.3
ON
Semiconductor
FAN5350UCX
RLOAD
Any
Feedback Loop
One key advantage of the non-linear architecture is that
there is no traditional feedback loop. The loop response to
changes in VOUT is essentially instantaneous, w hich
explains its extraordinary transient response. The
absence of a traditional, high-gain compensated linear
loop means that the FAN5350 is inherently stable over a
w ide range of LOUT and COUT.
LOUT can be reduced further for a given application,
provided it is confirmed that the calculated peak current
for the required maximum load current is less than the
minimum of the closed-loop current limit. The advantage is
that this generally leads to improved transient response,
since a small inductance allow s for a much faster
increase in current to cope w ith any sudden load demand.
The inductor can be increased to 2.2µH; but, for the same
reason, the transient response gets slightly degraded. In
that case, increasing the output capacitor to 10µF helps
s ignif ic antly .
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