Constant-current DC-DC LED driver

7 November 2001 Opto-Electronics

Linear Technology's LT1932 is a fixed frequency step-up DC-DC converter designed to operate as a constant-current source. Because it directly regulates output current, the LT1932 is ideal for driving light emitting diodes (LEDs) whose light intensity is proportional to the current passing through them, not the voltage across their terminals.

With an input voltage range of 1 to 10 V, the device works from a variety of input sources. The LT1932 accurately regulates LED current even when the input voltage is higher than the LED voltage, greatly simplifying battery-powered designs. A single external resistor sets LED current between 5 and 40 mA, which can then be easily adjusted using either a DC voltage or a pulsewidth modulated (PWM) signal. When the LT1932 is placed in shutdown, the LEDs are disconnected from the output, ensuring a quiescent current of under 1 µA for the entire circuit. The device's 1,2 MHz switching frequency permits the use of tiny, low-profile chip inductors and capacitors to minimise footprint and cost in space-conscious portable applications.

Memec SA

(021) 674 4103

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