The 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.
The 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.
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Analog LED drive with precision current control is part of the practice.
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