APP-D2

For devices with built-in current sink to drive an external LED APP-D2

Several of ETIC’s devices incorporate circuitry for driving an external LED. This feature consists of a current sink brought out to two pins. One pin is labeled LED, and the other RSET. These two pins are connected to external circuitry depending on the supply voltage, VCC, to be used in the application. Refer to the schematic diagrams below. For applications using a 5V supply, the ‘LED’ pin is connected directly to the cathode of the LED to be driven. The RSET pin is connected through a resistor to ground. The value of this resistor determines the sink current, which can be estimated as 1.8V/RSET. For higher supply voltages, an external transistor with adequate power dissipation should be added to the circuit. In this case the sink current will be 1.1V/RSET. The package pin numbers vary depending on the device, but are always labeled as shown here.

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