RT8060 查看數據表（PDF） - Richtek Technology
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RT8060 Datasheet PDF : 10 Pages
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Applications Information
The basic RT8060 application circuit is shown in Typical
Application Circuit. External component selection is
determined by the maximum load current and begins with
the selection of the inductor value and operating frequency
followed by CIN and COUT.
Inductor Selection
For a given input and output voltage, the inductor value
and operating frequency determine the ripple current. The
ripple current ΔIL increases with higher VIN and decreases
with higher inductance.
ΔIL
=
⎡
⎢⎣
VOUT
f ×L
⎤
⎥⎦
x
⎡⎢1−
⎣
VOUT
VIN
⎤
⎥
⎦
Having a lower ripple current reduces the ESR losses in
the output capacitors and the output voltage ripple. Highest
efficiency operation is achieved at low frequency with small
ripple current. This, however, requires a large inductor.
A reasonable starting point for selecting the ripple current
is ΔIL = 0.4(IMAX). The largest ripple current occurs at the
highest VIN. To guarantee that the ripple current stays
below a specified maximum, the inductor value should be
chosen according to the following equation :
RT8060
L=
⎡ VOUT ⎤
⎢⎣ f × ΔIL(MAX) ⎥⎦
x
⎡
⎢1−
VOUT
⎤
⎥
⎢⎣ VIN(MAX) ⎥⎦
A smaller inductor changes its current more quickly for a
given voltage drive than a larger inductor, resulting in faster
transient response. A larger inductor will reduce output
ripple and current ripple, but at the expense of reduced
transient performance and a physically larger inductor
package size. For this reason, a larger capacitor, C1, will
be required for larger inductor sizes.
The input regulator has an instantaneous peak current
clamp to prevent the inductor from saturating during
transient load or start-up conditions. The clamp is
designed so that it does not interfere with normal operation
at high loads and reasonable inductor ripple. It is intended
to prevent inductor current runaway in case of a shorted
output.
The DC winding resistance and AC core losses of the
inductor will also affect efficiency, and therefore available
output power. These effects are difficult to characterize
and vary by application. Some inductors and capacitors
that may be suitable for this application are listed in Table
below :
P/N
VLF5012ST-1R0N2R5
VLF5014ST-2R2M2R3
VLF3010A-1
VLF3012A
VLS2010E
VLS2012E
NR6045T1R0N
CB2016T2R2M
NR6020T2R2N
NR3015
LPS4018
D53LC
DB318C
WE-TPC Type M1
Length
(mm)
Max.
5
5
3
3
2.1
2.1
6
2.2
6
3
3.9
5
3.8
4.8
Width
(mm)
Max.
4.8
4.8
2.8
2.8
2.1
2.1
6
1.8
6
3
3.9
5
3.8
4.8
Table
Height
(mm)
Max.
1.2
1.4
1
1.2
1
1.2
4.5
1.8
2
1.5
1.7
3
1.8
1.8
Inductance
(μH)
L
1
2.2
2.2
2.2
2.2
2.2
1
2.2
2.2
2.2
3.3
3.3
3.3
3.3
RDC
(mΩ)
Max.
50
73
120
100
228
153
19
130
34
60
80
34
70
65
IDC
(A)
Max.
3.3
3
1
1
1
1
4.2
1
2.7
1.48
2.2
2.26
1.55
1.95
Supplier
TDK
TAIYO
CoilCraft
Toko
Wurth
DS8060-03 April 2011
www.richtek.com
7
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