This white LED driver electronic project circuit is designed using the
MAX1573 integrated circuit , manufactured by Maxim Semiconductor.This
white led driver circuit circuit drives as many as four white LEDs in
parallel from a 3.3V source, and adjusts the total LED current from 1mA
to 106mA, in 64 steps of 1dB each .To control the LED brightness, op amp
U2 monitors the difference between the high-side voltage and the wiper
voltage of digital potentiometer U1. The op amp then multiplies that
voltage by a gain to set the maximum output current.
Zero resistance at the pot's W1 terminal corresponds to minimum LED current, and therefore minimum brightness. Because the SET voltage is fixed (at 0.6V), any voltage change at the left side of R5 changes ISET, and the resulting change in LED currents changes their brightness level. R5 sets the maximum LED current: R5 = 215x0.6/ILED(Desired) (ILED is the current through one LED) .U1 integrated circuit is a digital potentiometer with logarithmic taper and an analog-voltage wiper for which each tap corresponds to 1dB of attenuation between H1 and W1 (pins 11 and 9).
Zero resistance at the pot's W1 terminal corresponds to minimum LED current, and therefore minimum brightness. Because the SET voltage is fixed (at 0.6V), any voltage change at the left side of R5 changes ISET, and the resulting change in LED currents changes their brightness level. R5 sets the maximum LED current: R5 = 215x0.6/ILED(Desired) (ILED is the current through one LED) .U1 integrated circuit is a digital potentiometer with logarithmic taper and an analog-voltage wiper for which each tap corresponds to 1dB of attenuation between H1 and W1 (pins 11 and 9).
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