LP3952 Datasheet, PDF (13/46 Pages) National Semiconductor (TI) – 6-Channel Color LED Driver with Audio Synchronization

LP3952
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SNVS518A – JULY 2007 – REVISED MARCH 2013
100 - internal current mirror multiplier
R_RGB- resistor value in Ohms
50Ω - internal resistor in the I_RGB input
For example if 22mA is required for maximum RGB current R_RGB equals to:
R_RGB=100×1.23V / I_MAX–50Ω=123V / 0.022A–50Ω=5.54kΩ
(2)
Each individual RGB output has a separate maximum current programming. The control bits are in registers
RGB1 max current and RGB2 max current (12H and 13H) and programming is shown in table below. The
default value after reset is 00b.
IR1[1:0], IG1[1:0],
IB1[1:0], IR2[1:0],
IG2[1:0], IB2[1:0]
00
01
10
11
Maximum
Current/Output
0.25 × I_MAX
0.50 × I_MAX
0.75 × I_MAX
1.00 × I_MAX
SWITCH MODE
The switch mode is used if there is a need to connect parallel LEDs to output or if the RGB output current needs
to be increased.
Please note that the switch mode requires an external ballast resistors at each output to limit the LED current.
The switch/current mode and on/off controls for RGB are in the RGB_ctrl register (00H).
Table 1. RGB_ctrl Register (00H) (1.65V ≤ V_DDIO ≤ V_DD1,2V) (unless otherwise noted)
CC_RGB1
1 R1, G1 and B1 are switches → limit current with ballast resistor
bit7
0 R1, G1 and B1 are constant current sinks, current limited internally
CC_RGB2
1 R2, G2 and B2 are switches → limit current with ballast resistor
bit6
0 R2, G2 and B2 are constant current sinks, current limited internally
r1sw
1 R1 is on
bit5
0 R1 is off
g1sw
1 G1 is on
bit4
0 G1 is off
b1sw
1 B1 is on
bit3
0 B1 is off
r2sw
1 R2 is on
bit2
0 R2 is off
g2sw
1 G2 is on
bit1
0 G2 is off
b2sw
1 B2 is on
bit0
0 B2 is off
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