SP6682EB Exar Corporation, SP6682EB Datasheet - Page 8

• Manufacturer Part Number: SP6682EB
• Description: EVAL BOARD FOR SP6682
• Manufacturer: Exar Corporation

Specifications of SP6682EB

• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Product: Display Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

use this feature, divider resistors should be
chosen according to the specific applica-tion,
as shown in Figure 16.
The guideline for divider resistor selections is
as follows: For high input voltage, the SP6682
will work in X1.5 mode. When the input
voltage drops to the V
will switch to X2 mode automati-cally. The V
threshold voltage for mode change can be
calculated by:
Where V
number of the white LEDs, R
resistance of the SP6682. The equation for the
voltage divider R1 and R2 with V
is:
B
Dimming control can be achieved by applying
a PWM control signal to the EN/PWM pin. The
brightness of the white LEDs is con-trolled by
increasing and decreasing the duty cycle of
the PWM signal. While the operating frequency
© 2009 Exar Corporation
RIGHTNESS
Manufacturer
Murata
Murata
V
TDK
TDK
Fig. 16: Programming the V
TH
F
=
and M are the forward voltage and
(
V
C
F
ONTROL
+
. 0
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GRM219R60J475KE01D
306
C2012X5R1A225K
C2012X5R0J475K
Part Number
+
TH
U
1
M
5 .
threshold voltage, it
SING
×
MODE
I
OUT
LED
PWM
H
Resistors
H
×
is the output
MODE
Table 1: Suggested Low ESR Capacitors
i
i
R
g
g
OUT
h
h
= 1.25V
E
E
)
f
f
f
f
i
i
c
c
TH
i
i
Capacitance
e
e
4.7µF/6.3V
2.2µF/6.3V
4.7µF/6.3V
2.2µF/10V
8/13
Voltage
n
n
c
c
y
y
which can be expressed as R1:
For the typical SP6682 application, using
V
will
R1=158kΩ.
C
Ceramic capacitors are recommended for their
inherently low ESR, which will help produce
low peak to peak output ripple, and reduce
high frequency spikes.
The fly capacitor controls the strength of the
charge pump. Selection of the fly capacitor is
a trade-off between the output voltage ripple
and the output current capability. Decreasing
the fly capacitor will reduce the output voltage
ripple because less charge will be delivered to
the output capacitor. However, smaller fly
capacitors lead to larger output resistance,
thus decreasing the out-put current capability
and
capacitors as close to the SP6682 as possible
for layout. Increasing the value of the input
and output capaci-tors could further reduce
the input and out-put ripple.
Refer to Table 1 for some suggested low ESR
capacitors.
range of the PWM control is from 60Hz to
700Hz,
brightness frequency range of the PWM signal
is from 60Hz to 200Hz. A repetition rate of at
least 60Hz is required to prevent flicker.
W
W
F
APACITOR
=3.6V, M=4, I
h
h
i
i
the
t
be
t
e
e
L
L
E
3.24V.
E
the
circuit
D
D
S
V
Size/Type
R
ELECTION
Capacitor
0805/X5R
0805/X5R
0805/X5R
0805/X5R
TH
C
C
1
LED
h
h
=
=
recommended
a
a
⎛
⎜
⎝
. 1
effi-ciency.
=15mA, R
Select
. 1
r
r
V
25
g
g
TH
25
e
e
×
−
⎛
⎜
⎝
P
P
1
1
u
u
+
⎞
× ⎟
⎠
R2=100kΩ,
m
m
R
R
OUT
R
1
2
ESR @ 100KHz
p
p
2
Place
⎞
⎟
⎠
=16Ω, the V
R
R
0.030Ω
0.020Ω
0.030Ω
0.020Ω
S
S
e
e
maxim-um
P
P
g
g
Rev. 2.0.0
u
6
u
6
all
l
l
6
6
a
a
then
8
t
8
t
the
o
o
2
2
TH
r
r