LED driver provides software-controlled intensity


Posted on Apr 11, 2012

This design reconfigures the APD-bias IC, IC1, to allow its low-voltage DAC output to modulate the high-voltage, current-sense feedback via a high-voltage-output transconductance stage comprising Q2 and Q3. These two complementary transistors provide first-order temperature-compensation sufficient for the application. Vendors in recent years have introduced many ICs for driving LEDs, but the problem of driving serial chains of LEDs has received less attention. One approach to that problem adapts a bias-supply IC for APDs (avalanche photodiodes) to provide adjustable-current, software shutdown, and logic indication of open-circuit faults (Figure 1).






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