SN74LVC2G34: Short Circuit Current

The risk is that the device will be damaged (short circuit or open circuit or one after the other).

Two outputs in parallel would allow 100 mA.

Hey Mark,

Clemens is correct. I just wanted to add that there are a few options in this scenario:

(1) Increase the resistor value to 75 ohms -- most LEDs will still produce a very good amount of light even at half their rated current, and this would be the cheapest/easiest solution to prevent any damage. At 71 ohms (75 - 5%) and 3.3V, the output short circuit current is limited to 46.5mA, which is within the device's capabilities.

(2) Use one SN74LVC2G34 per LED and parallel both channels. The device can support up to 100 mA total current, and you can parallel channels within the same device (don't try it with multiple devices though, as this can introduce timing differences).

(3) I put this last since it is least likely to be useful - but it's still worth mentioning.  You might be able to increase the LED supply voltage to 5V -- in this scenario, 1.7V additional falls across the limiting resistor, which allows for a larger resistor value at the same current output, and thus ends up with a short-circuit safe output. Assuming 5V and 2.3V Vf at 20mA, the resistor needs to be 135 ohms, which results in short circuit current of 37 mA.