Datasheet

50
60
70
80
90
100
10.0 15.0 20.0 25.0 30.0
InputVoltage-V
Efficiency-%
+
+
ISNS
VDD
TPS40200-HT
SGLS400C –OCTOBER 2009–REVISED DECEMBER 2012 www.ti.com
Application 3: Wide Input Voltage LED Constant-Current Driver
This application uses the TPS40200 as a buck controller that drives a string of LED diodes. The feedback point
for this circuit is a sense resistor in series with this string. The low 0.7-V reference minimizes power wasted in
this resistor, and maintains the LED current at a value given by 0.7/R
SENSE
. As the input voltage is varied, the
duty cycle changes to maintain the LED current at a constant value so that the light intensity does not change
with large input voltage variations.
Figure 48. Wide Input Voltage-Range LED Driver
Figure 49. Efficiency vs Input Voltage
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