LP3954 Datasheet, PDF (13/60 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

LP3954
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Vin = 3.6V, Vout = 5.0V if not otherwise stated
Output Voltage vs Load Current
5.2
5.0
4.8
4.6
V_IN = 3V
4.4
f = 2 MHz
L - TDK VLF0410 4.7 PH
4.2
C_IN = C_OUT = 10 PF
4.0
3.8
3.6
0
100 200 300 400 500
OUTPUT CURRENT (mA)
Figure 12.
SNVS340D – JUNE 2005 – REVISED MARCH 2013
Efficiency At Low Load vs Autoload
90
80
70
60
50
40
Autoload ON
Autoload OFF
30
20
0
5 10 15 20 25 30
LOAD CURRENT (mA)
Figure 13.
Functionality of Color LED Outputs (R1, G1, B1; R2, G2, B2)
LP3954 has 2 sets of RGB/color LED outputs. Both sets have 3 outputs and the sets can be controlled in 4
different ways:
1. Command based pattern generator control (internal PWM)
2. Audio synchronization control
3. Direct ON/OFF control
4. External PWM control
By using command based pattern generator user can program any kind of color effect patterns. LED intensity,
blinking cycles and slopes are independently controlled with 8 16-bit commands. Also real time commands are
possible as well as loops and step by step control. If analog audio is available on system, the user can use
audio synchronization for synchronizing LED blinking to the music. The different modes together with the
various sub modes generate very colorful and interesting lighting effects. Direct ON/OFF control is mainly for
switching on and off LEDs. External PWM control is for applications where external PWM signal is available
and required to control the color LEDs. PWM signal can be connected to any color LED separately as shown
later.
COLOR LED CONTROL MODE SELECTION
The RGB_SEL[1:0] bits in the Enables register (08H) control the output modes for RGB1 (R1, G1, B1) and RGB2
(R2, G2, B2) outputs. The following table shows the RGB_SEL functionality.
RGB_SEL[1:0]
00
01
10
11
Audio Sync Connected To
none
RGB1
RGB2
RGB1 & RGB2
Command Based Pattern Generator
Connected To
RGB1 & RGB2
RGB2
RGB1
none
RGB Control register (00H) has control bits for direct on/off control of all color LEDs. Note that the LEDs have
to be turned on in order to control them with audio synchronization or pattern generator.
The external PWM signal controls any LED depending on the control register setup. The controls are in the Ext.
PWM Control register (address 07H) except the FLASH control in HC_Flash (10H) register as follows:
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