Also I think the chip needs its 0V connecting to the earth, and its "COM" needs connecting to the +V supply you're using. (These are needed internally for the chip itself for some reason.)
You also should probably have a resistor in series with the LED to limit the current, unless the LED can take the full voltage of the power supply. I'd just connect it all directly to the +5V supply of the raspi if possible, with the appropriate resistor on the LED to stop the full 5V burning it out.
(Calculating the appropriate resistor depends on the voltage & current it needs to dump - depends what the LED is rated at.)
EDIT: maybe have a look at the circuit on p7 of this: