The UBA2213 has a boost function. For the first 40 to 60 seconds after ignition, the lamp-current will be about 1.8x the nominal current. This feature is specifically useful for amalgam type of burners. These are known for a slow start where it can take several minutes to reach 80% of the final light output. If the IC temperature reaches 120°C the boost is switched off earlier than the boost time set by the external capacitor. The CSW capacitor is used for preheat, boost timing and feedback control during operation. There is no feedback control during boost, therefore the IC will go to a 1.5x lower frequency than its Fmin, so typical boost will be around 27 kHz. Since the UBA2213 makes its boost time with the preheat timing capacitor CSW the boost time and preheat time are related.