FLS0116 FAIRCHILD [Fairchild Semiconductor], FLS0116 Datasheet - Page 7

• Manufacturer Part Number: FLS0116
• Description: MOSFET Integrated Smart LED Lamp Driver IC with PFC Function
• Manufacturer: FAIRCHILD [Fairchild Semiconductor]

© 2012 Fairchild Semiconductor Corporation
FLS0116 • Rev. 1.0.0
Dimming Function
The FLS0116 uses the ADIM pin for analog or 0V to
10V dimming. The peak voltage of internal reference,
which is DAC_OUT signal in Figure 5, is changed by the
V
level according to the operating mode.
Inductor Design
The fixed internal duty ratio range is below 50%, or
around 400ns, from a timing point of view. The range is
dependent on the input voltage and number of LEDs in
its string.
Minimum duty is calculated as:
ADIM
where:
η
V
V
n
D
V
IN(max)
f
0.36 V
min
DA _ OU
0.5V
level, as shown in Figure 7, and has different peak
=
η
= efficiency of system;
= maximum input voltage;
Figure 8. DCM and CCM Operation
= forward drop voltage of LED; and
= LED number in series connection.
⋅
Figure 7. V
n
V
⋅
in
0. 5V
V
(max)
f
ADIM
vs. V
DAC_OUT(peak)
3.5V
AC
DC
V
ADI
(1)
7
In DCM Mode, inductance is:
If the peak current is fixed at 350mApk, the formula for
the peak current is:
In CCM Mode, determine the necessary inductance
using Equations (2) and (3). Assuming the high-
frequency current ripple (∆i
average LED current in CCM is defined as:
LED RMS current determined as:
L
I
I
I
Figure 9. Typical Performance Characteristics
=
o
LED
LED
m
(
peak
(
(
=
(
I
rms
average
LED
)
n
)
=
=
⋅
2
(
Δ
V
)
PK
1
2
i
=
con
(
f
f
)
Δ
s
I
−
⋅
i
LED
+
rip
Δ ⋅
1 (
Δ
2
(
Δ
rms
(
−
i
PK
i
2
i
rip
)
rip
rip
2
D
)
+
)
−
=
Δ
min
Δ
350
i
[mA]
con
2
)
i
rip
(
rms
[
[mA]
H
)
)
[mA]
]
=
rip
1
2
) as in the DCM, the
(
I
LED
2
(
PK
)
+
I
LED
(
PK
www.fairchildsemi.com
)
2
−
Δ
i
rip
)
(2)
(3)
(4)
(5)
(6)