LP3954 Datasheet, PDF (23/60 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

LP3954
www.ti.com
SNVS340D – JUNE 2005 – REVISED MARCH 2013
100
BLUE GREEN
90
80
70
60
50
40
30
20
RED
10
0
0 10 20 30 40 50 60 70 80 90 100
INPUT AMPLITUDE (%)
Figure 18. Overlapping mode MODE_CTRL[1:0] =
[10]
5.00
3.00
2.50
2.00
1.50
1.00
0.50
0.30
0.25
0.20
0.15
0.10
0.05
0 3 6 9 12 15 18 21
GAIN (dB)
Figure 19. Peak Input Signal Level
Range vs Gain Setting
RGB OUTPUT SYNCHRONIZATION TO EXTERNAL CLOCK
The RGB pattern generator and high current flash driver timing can be synchronized to external clock with
following configuration.
1. Set PWM_SYNC bit in Enables register to 1
2. Feed PWM_SYNC pin with 5 MHz clock
By this the internal 5 MHz clock is disabled from pattern generator and flash timing circuitry.
The external clock signal frequency will fully determine the timings related to RGB and Flash.
Note: The boost converter will use internal 5 MHz clock even if the external clock is available.
RGB Driver Typical Performance Characteristics
RGB DRIVER ELECTRICAL CHARACTERISTICS (R1, G1, B1, R2, G2, B2 OUTPUTS)
I_LEAKAGE
I_MAX(RGB)
R_SW
ƒ_RGB
Parameter
R1, G1, B1, R2, G2, B2 pin
leakage current
Maximum recommended sink
current ⁽¹⁾
Accuracy at 37mA
Current mirror ratio
RGB1 and RGB2 current
mismatch
Switch resistance
RGB switching frequency
Test Conditions
CC mode
SW mode
R_RGB=3.3 kΩ ±1%, CC mode
CC mode
I_RGB=37mA, CC mode
SW mode
Accuracy proportional to internal
clock freq.
If external SYNC 5MHz is in use
(1) Note: RGB current should be limited as follows:
constant current mode – limit by external R_RGB resistor;
switch mode – limit by external ballast resistors
Min
Typ
Max
Unit
0.1
1
µA
40
mA
50
mA
±5
%
1:100
±5
%
2.5
4
Ω
18.2
20
21.8
kHz
20
kHz
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