LP3942YQ NSC [National Semiconductor], LP3942YQ Datasheet - Page 11

• Manufacturer Part Number: LP3942YQ
• Description: The Dual RGB LED Controller with 1.5x/2x Charge Pump and SPI Interface
• Manufacturer: NSC [National Semiconductor]

RGB Functionality
The brightness control is logarithmic and is programmed as
follows.
Color[3:0]
Bright
[2:0]
000
001
010
011
100
101
110
111
0000
0001
0010
0100
0101
1000
1001
1010
0011
0110
0111
1011
1100
1101
1110
1111
Brightness
active/cycle [%]
Color
1.56
3.12
6.25
12.5
25.0
50.0
[%]
100
0
Red
100
50
50
33
50
25
25
75
75
25
25
0
0
0
0
0
(Continued)
Max Brightness
Ratio to
1/64
1/32
1/16
active/cycle [%]
1/8
1/4
1/2
1/1
RGB Framing with 50% Intensity
0
Green
100
50
50
33
25
50
25
25
75
75
25
0
0
0
0
0
11
Non-Overlapping Mode
The non-overlapping mode has 16-programmed colors (dif-
ferent R, G and B ratio → different color). Since the R, G and
B are split in to non-overlapping slots the output current
through the RGB LED can be calculated by following equa-
tion:
The 16 colors can be selected as follows. Please note that
exact color depends on LED current and type.
active/cycle [%]
Blue
100
50
50
33
25
25
50
25
25
75
75
0
0
0
0
0
B = Brightness [%] (see table below)
I
AVG
C = Color [%] (see table below)
= (C
R
* I
R
(depends on RGB LED type)
+ C
G
* I
G
RGB Color
dark green
med green
green/blue
blue/green
+ C
dark pink
lt orange
maroon
lt green
orange
yellow
purple
lt blue
green
white
blue
red
B
* I
B
)*B,
20129209
www.national.com