16-Bit, Single-Supply LED Current Driver with Less than В±1 LSB Integral and Differential Nonlinearity (CN0370)
The circuit in Figure 1 is a complete single-supply, low noise LED current source driver controlled by a 16-bit digital-to-analog converter (DAC). The system maintains ±1 LSB integral and differential nonlinearity and has a 0.1 Hz to 10 Hz noise of less than 45 nA p-p for a full-scale output current of 20 mA.
The innovative output driver amplifier eliminates the crossover nonlinearity normally associated with most rail-to-rail input op amps that can be as high as 4 LSBs or 5 LSBs for a 16-bit system.
This industry-leading solution is ideal for pulse oximetry applications where 1/f noise superimposed on the LED brightness levels affects the overall accuracy of the measurement.
Total power dissipation for the three active devices is less than 20 mW typical when operating on a single 5 V supply.
Figure 1. ±1 LSB Linear 16-Bit LED Current Source Driver (Simplified Schematic: All Connections and Decoupling Not Shown)
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