LM3697_15 Datasheet, PDF (29/43 Pages) Texas Instruments – High-Efficiency Three-String White LED Driver

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LM3697
SNOSCS2C – NOVEMBER 2013 – REVISED OCTOBER 2015
V_IN = 3.6 V, full-scale current = 20.2 mA, LEDs are WLEDs part # SML-312WBCW(A), Typical Application Circuit , T_A = 25°C
unless otherwise specified. Efficiency is V_OUT × (I_HVLED1 + I_HVLED2 + I_HVLED3)/(V_IN × I_IN), matching curves are (ΔI_{LED_MAX}/I_{LED_AVE}).
Three String, L=4.7µH, 500kHz
90%
88%
86%
84%
82%
80%
78%
76%
74%
72%
70%
0.00 12.00 24.00 36.00 48.00 60.00
ILED (mA)
C002
Top to Bottom: 3x3, 3x4, 3x5, 3x6, 3x7 (LEDs)
Three String, L=4.7µH, 1MHz
90%
88%
86%
84%
82%
80%
78%
76%
74%
72%
70%
0
12
24
36
48
60
ILED (mA)
C002
Top to Bottom: 3x3, 3x4, 3x5, 3x6, 3x7 (LEDs)
Figure 42. Boost Efficiency vs I_LED
Figure 43. Boost Efficiency vs I_LED
Two String, L=4.7µH, 500kHz
90%
88%
86%
84%
82%
80%
78%
76%
74%
72%
70%
0
12
24
36
48
ILED (mA)
C002
Top to Bottom: 2x3, 2x4, 2x5, 2x6, 2x7, 2x8, 2x9, 2x10 (LEDs)
Figure 44. Boost Efficiency vs I_LED
100
10
1
0.1
0.01
Two String, L=4.7µH, 1MHz
90%
88%
86%
84%
82%
80%
78%
76%
74%
72%
70%
0
12
24
36
48
ILED (mA)
C002
Top to Bottom: 2x3, 2x4, 2x5, 2x6, 2x7, 2x8, 2x9, 2x10 (LEDs)
Figure 45. Boost Efficiency vs I_LED
7.00%
6.00%
5.00%
4.00%
3.00%
2.00%
1.00%
0.00%
-1.00%
m1-2
m2-3
m3-1
BRIGHTNESS CODE
C001
Exponential Mapping
Figure 46. H_VLED Current vs. Brightness Code
BRIGHTNESS CODE
C001
Exponential Mapping
Figure 47. H_VLED Matching Vs. Brightness Code
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