UBA2021_4

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 04 — 25 July 2008

6 of 16

NXP Semiconductors

UBA2021

630 V driver IC for CFL and TL lamps

7.9 Capacitive mode protection

When the preheat mode is completed, the IC will protect the power circuit against losing

the zero voltage switching condition and getting too close to the capacitive mode of

Consequently the frequency increases as long as the capacitive mode is detected. The

frequency decreases down to the feed-forward frequency if no capacitive mode is

detected. Frequency modulation is achieved via the CI-pin.

7.10 IC supply

starts oscillating. After the preheat phase is finished, the pin is connected to an internal

the VS-pin will now be charged via the snubber capacitor CS7. Excess charge is drained

7.11 Minimum gate-source voltage of T1 and T2

bootstrap switch during the on periods of T2. The IC stops oscillating at a voltage level

The drive voltage at G2 will exceed the drive voltage of the high side driver.

Fig 6.

Feed-forward frequency

mgs993

bottom

frequency

feed-forward

range

f

(kHz)

Table 4.

Minimum gate-source voltages

FREQUENCY

VOLTAGE

< 75 kHz

8 V (min)

75 kHz to 85 kHz

7 V (min)

≥ 85 kHz

6 V (min)