Circuit Regulates White-LED Bias Current

Posted on Nov 3, 2012

The compact circuit (Figure 1) overcomes these problems. The regulated buck/boost charge pump in a small µMAX package (U1) has a 100mA output-current capability. Configured as shown, the circuit directly regulates bias current flowing through the white LED. By biasing multiple white LEDs in parallel, it can provide good light distribution. The U1`s design eliminates the troublesome input-output path in shutdown, and its SHDN input (Pin 2) lets the user turn the backlight on and off. The circuit also includes a power-OK output (POK) for signaling a microprocessor when the backlight is available.

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