LD1204 is a driver ASIC that used in automotive and motorcycle direction indicator lamp unit. The IC has a frequency conversion function, when the load current is less than the internal set threshold, the flasher frequency doubling. At the same time it has multiple protection functions, such as over-current protection, over-temperature protection, high-voltage clamp, under-voltage protection and battery reverse protection, to ensure that in different circumstances the normal functions of the chip. Chip peripheral circuit is simple, just a external capacitor (220uF,10V ) that connected with the CEXT pin and OUT pin, while Vcc pin is connected to the positive terminal of the battery, the OUT pin connected to a switch ( which set between the OUT pin of chip and the direction indicator lamp ). When the switch turn on, chip generates a duty ratio of about 50% for the direction indicator control signal.