UBA2071ATS datasheet(22/35 Pages) NXP

22 / 35 page

UBA2071_A_1

Product data sheet

Rev. 01 — 23 June 2008

22 of 35

NXP Semiconductors

UBA2071; UBA2071A

Half bridge control IC for CCFL backlighting

duration longer than tspike(min). Each spike will trigger an internal one-shot, which signals to

the control circuits that arcing has been detected. When arcing is detected, PWM dimming

is disabled and the fault timer is started.

8.14.8 Ignition Failure (IF)

When the current control loop comes close to its regulation point, the lamps are assumed

to be on (ignited). This is when the average absolute voltage on the IFB pin is above

Vth(lod)(IFB). If the lamps are not on when the ignition sweep is ﬁnished, (switching

frequency has reached fsw(min)), then an ignition failure is detected, PWM dimming is

disabled and the fault timer is started.

8.14.9 The NONFAULT pin

The NONFAULT pin provides bidirectional signalling of the fault status between the IC and

any external circuit. When no fault is detected, the voltage on the pin is pulled high to

Voc(NONFAULT) by an internal current source.

An external circuit can signal to the IC that a fault has been detected by pulling a current

larger than Itrig(I)NONFAULT from the NONFAULT pin. The IC will detect the current drawn

from the pin and start the fault timer. To prevent interference with the PWM dimming, the

IC will only look at the NONFAULT pin during the period when the lamp current regulation

loop is closed (when

When the IC detects an internal fault, see Section 8.14.2 to Section 8.14.8), it signals this

via the NONFAULT pin by pulling the pin down (after the fault output delay time td(o)fault)).

At this point the IC can no longer detect the external fault. However, by then the fault timer

is already running.

Fig 17. Input and output levels at the NONFAULT pin

CSWP

CVFB

Isink(NONFAULT)

NONFAULT

pin current

NONFAULT

pin voltage

Vtrig(I)NONFAULT

Voc(NONFAULT)

in: low (active)

out: high (inactive)

in: unknown

out: low (active)

Itrig(I)NONFAULT

Isc(NONFAULT)

in: high (inactive)

out: high (inactive)

load line

014aaa113

1 V

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