LM3557 Datasheet, PDF (6/19 Pages) National Semiconductor (TI) – Step-Up Converter for White LED Applications

LM3557
SNVS338B – NOVEMBER 2004 – REVISED FEBRUARY 2013
www.ti.com
TYPICAL PERFORMANCE CHARACTERISTICS
( Circuit in Figure 1: L = DO1608C-223, D = SS16, and LED = LWT67C. Efficiency: η = P_OUT/P_IN = [(V_OUT – V_Fb) * I_OUT]/[V_IN *
I_IN]. T_A= 25°C, unless otherwise stated).
I_Q (SWITCHING) vs TEMPERATURE
3
V_IN = 4.2V
V_IN = 4.5V
2.5
V_IN = 3.6V
2
V_IN = 2.7V
1.5
1
0.5
0
-40
I_LED = 20 mA
-20
0
25
40
85
TEMPERATURE (°C)
Figure 4.
SWITCHING FREQUENCY vs TEMPERATURE
1.26
1.25
1.24
1.23
V_IN = 2.7V
V_IN = 3.6V
1.22
1.21
V_IN = 4.5V
1.20
1.19
1.18
1.17
1.16
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (^oC)
Figure 5.
En PIN CURRENT vs En PIN VOLTAGE
3
2.5
25°C
2
1.5
-40°C
1
25°C
0.5
85°C
85°C
0
-40°C
0 0.2 0.4 0.6 0.8 1 1.2 1.4 2 3
V_EN (V)
Figure 6.
CURRENT LIMIT vs TEMPERATURE
0.95
0.9
0.85
0.8
V_IN = 3.6V
V_IN = 4.5V
0.75
0.7
V_IN = 3V
0.65
0.6
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (^oC)
Figure 7.
OVP PIN CURRENT vs TEMPERATURE
4.25
4.20
4.15
V_IN = 3.6V
4.10
4.05
4.00
3.95
3.90
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (^oC)
Figure 8.
R_DS(ON) (Figure 3: N1) vs TEMPERATURE
1.4
1.2
V_IN = 3.6V
1
0.8 ^{VIN = 2.7V}
0.6
V_IN = 4.5V
0.4
0.2
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (^oC)
Figure 9.
6
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