UBA2071_A_1

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 01 — 23 June 2008

8 of 35

NXP Semiconductors

UBA2071; UBA2071A

Half bridge control IC for CCFL backlighting

voltage.

The maximum current that is allowed to be delivered by the start-up current source is

voltage as stated in Table 4.

8.3 Enable

The UBA2071 or UBA2071A can be activated or set to standby via the EN pin. If the

DC blocking capacitor charging mode (see Section 8.8). When the voltage on the EN pin

Section 8.8) and subsequently go to normal operation mode again.

8.4 The oscillator

The UBA2071 and UBA2071A have an internal voltage controlled sawtooth oscillator, see

Figure 5. Its frequency inverses in proportion to the capacitor connected to the CF pin.

The IC switches GL on and GH off during one oscillator period and GL off and GH on

during the next oscillator period. This results in a half bridge voltage with a frequency

duty cycle of exactly 50 %.

The oscillator frequency is controlled by changing the charge current at the CF pin. By

changing the frequency the lamp current is controlled. It is also used to limit the

transformer output voltage and for gradually switching the lamps on and off during PWM

dimming.

2.

When both GH and GL are low during the lamps off period of PWM dimming (so PWMD is high), the IC will wait with entering the

standby state until PWMD becomes low again and GL can be made high.