Analog RGB LED Driver for Optical Diagnostics (No-PWM)

Challenge: RGB LED driver for an optical diagnostic instrument. Color accuracy has to be repeatable across units and temperature because the diagnostic algorithm depends on consistent illumination wavelengths. Solution: Pure analog current regulation, no PWM. PWM would cause flicker artifacts in the optical measurement. Each RGB channel has its own precision current source with temperature-compensated feedback. The linear current sources are fed by a switching pre-regulator that tracks just above the LED forward voltage, keeping power dissipation low while maintaining clean, ripple-free drive. Results: Channel-to-channel current matching within 0.5%. The client calibrates each unit once at the factory and the readings hold across the operating temperature range.