Constant Current LED Driver (Rev. C) - Educypedia
Constant Current LED Driver (Rev. C) - Educypedia
Constant Current LED Driver (Rev. C) - Educypedia
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TPS61042<br />
SLVS441C–DECEMBER 2002–REVISED MARCH 2007<br />
r ds(on) - On-State Resistance - Ω<br />
3.0<br />
2.5<br />
2.0<br />
1.5<br />
1.0<br />
0.5<br />
0.0<br />
V out<br />
10V/Div<br />
CTRL<br />
1V/Div<br />
Input <strong>Current</strong><br />
100mA/Div<br />
V sw<br />
5V/Div<br />
V out<br />
50mV/Div<br />
<strong>LED</strong> <strong>Current</strong><br />
20mA/Div<br />
r ds(on) <strong>LED</strong> Switch (Q2) Average <strong>LED</strong> <strong>Current</strong><br />
vs vs<br />
Input Voltage PWM Duty Cycle on CTRL Pin<br />
1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0<br />
V I - Input Voltage - V<br />
50s/Div<br />
2.5s/Div<br />
T A = 25°C<br />
I O - Output <strong>Current</strong> - mA<br />
20<br />
15<br />
10<br />
5<br />
0<br />
V sw<br />
5V/Div<br />
V out<br />
500mV/Div<br />
<strong>LED</strong> <strong>Current</strong><br />
20mA/Div<br />
V sw<br />
5V/Div<br />
V out<br />
500mV/Div<br />
<strong>LED</strong> <strong>Current</strong><br />
20mA/Div<br />
f PWM = 100 Hz f PWM = 50 kHz<br />
f PWM = 25 kHz<br />
www.ti.com<br />
0 20 40 60 80 100<br />
Duty Cycle - %<br />
Figure 10. Figure 11.<br />
Softstart PFM Operation<br />
2.5s/Div<br />
Figure 12. Figure 13.<br />
Bust Mode Operation PWM Dimming<br />
25s/Div<br />
Figure 14. Figure 15.<br />
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