LM3537_13 Datasheet, PDF (25/33 Pages) Texas Instruments – 8-Channel WLED Driver with Four Integrated LDOs

LM3537
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Current Control Registers
SNVS634B – JUNE 2011 – REVISED MAY 2013
A0 GROUP A BRIGHTNESS
This is the LED driver current control register for Group A. The register is effective when the ALS isn't used. The
resolution is 7 bits, so in linear dimming mode the step size from zero up to full brightness is fixed (25.0mA/127)
= 197 µA. Exponential dimming scheme provides a more fine-grained level of control over low level LED
currents. Group A exponential dimming curve current can be approximated by the following equation (where N =
the decimal value stored in the Group A Brightness register):
I_LED (mA) | 25 x 0.85 ^{[44 ± {(N+1)/2.91}]}
(1)
Current vs. code is shown below.
Figure 10. LED current (typ.) vs. register code, exponential dimming curve
B0 GROUP B BRIGHTNESS
Bits [2:0] set the GroupB Brightness Levels, as shown in below:
dxb[2]
1
1
1
1
0
0
0
0
dxb[1]
1
1
0
0
1
1
0
0
Table 6. Group B Brightness Levels
dxb[0]
1
0
1
0
0
0
1
0
GroupB LED Current (typ.)
25.0 mA
17.5 mA
15.0 mA
12.5 mA
10.0 mA
7.5 mA
5.0 mA
2.5 mA
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