LM3509SDEV National Semiconductor, LM3509SDEV Datasheet - Page 6

• Manufacturer Part Number: LM3509SDEV
• Description: BOARD EVALUATION FOR LM3509SD
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3509SDEV

• Current - Output / Channel: 40mA
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 21V
• Features: Dimmable, I²C Interface
• Voltage - Input: 2.7 ~ 5.5V
• Utilized Ic / Part: LM3509
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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Brightness Registers (BMAIN and
BSUB)
With the UNI bit (General Purpose register) set to 0 (Non-
Unison mode) both brightness registers (BMAIN and BSUB)
independently control the LED currents I
spectively. BMAIN and BSUB are both 8 bit, but with only the
5 LSB’s controlling the current. The three MSB’s are don’t
cares. The LED current control is designed to approximate an
exponentially increasing response of the LED current vs in-
creasing code in either BMAIN or BSUB (see Figure 10).
Program I
to GND, where:
With the UNI bit (General Purpose register) set to 1 (Unison
mode), BSUB is disabled and BMAIN sets both I
FB
FB
Table 4. I
. This prevents the independent control of I
, however matching between current sinks goes from typi-
BMAIN or BSUB Brightness
LED_MAX
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
Data
LED
by connecting a resistor (R
vs. Brightness Register Data
% of ILED_MAX
MAIN
0.000%
0.125%
0.625%
1.000%
1.125%
1.313%
1.688%
2.063%
2.438%
2.813%
3.125%
3.750%
4.375%
5.250%
6.250%
7.500%
and I
SET
MAIN
MAIN
) from SET
SUB/FB
and I
and I
SUB/
SUB/
re-
6
BMAIN or BSUB Brightness Data
cally 1%(with UNI = 0) to typically 0.15% (with UNI = 1). Figure
8 and Figure 9 show the register descriptions for the Bright-
ness MAIN and Brightness SUB registers. Table 4 and Figure
10 show I
age of I
FIGURE 8. Brightness MAIN Register Description
FIGURE 9. Brightness SUB Register Description
LED_MAX
MAIN
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
and/or I
.
SUB/FB
vs. brightness data as a percent-
% of ILED_MAX
100.000%
10.000%
12.500%
15.000%
16.875%
18.750%
22.500%
26.250%
31.250%
37.500%
43.750%
52.500%
61.250%
70.000%
87.500%
8.750%
30011110
30011109