UBA2071ATS datasheet(6/35 Pages) NXP

6 / 35 page

UBA2071_A_1

Product data sheet

Rev. 01 — 23 June 2008

6 of 35

NXP Semiconductors

UBA2071; UBA2071A

Half bridge control IC for CCFL backlighting

Functional description

The UBA2071 and UBA2071A are designed to drive a half bridge inverter (as shown in

Figure 3) with a resonant load. The load consists typically of a transformer with CCFLs or

EEFLs.

The IC has an AC lamp current sense input (IFB). It regulates the average absolute value

of the lamp current by varying its switching frequency. The load is presumed to be

inductive: higher frequency results in lower lamp current.

The UBA2071 and UBA2071A include a PWM dimming function. The ICs switch the

lamps on and off with a frequency lower than the lamp current frequency but higher than

what the human eye can see. The light output of the lamps can be set by setting the ratio

of the on-time and off-time.

These ICs have several forms of protection and the next chapters will describe each

function in more detail.

NONFAULT 12

status signal

input/output

The IC signals a fault condition to external circuits by pulling this pin low. Also

external circuits can signal a fault condition to the IC by pulling this pin low.

PWMD

digital PWM dimming

input/output

Digital output of internally generated PWM signal if a capacitor is connected

to the CPWM pin.

Digital input of PWM signal if the CPWM pin is connected to signal ground.

Remark: The signal on the PWMD pin is active low, so low voltage on the

PWMD pin means lamps are on.

PWMA

analog PWM dimming

input

The duty cycle of the internally generated PWM signal is proportional to the

voltage on this pin.

chip enable input

A low voltage on this pin will reset and shut down the IC. This pin is also used

to select between DC blocking capacitor charging mode and normal

operation.

VDD

supply input

A buffer capacitor must be connected between this pin and power ground.

PGND

power ground

return for the low-side driver.

low-side driver output

Gate connection of the low-side power switch.

n.c.

not connected

HV spacer pin.

n.c.

not connected

HV spacer pin.

n.c.

not connected

HV spacer pin.

high-side source

connection

Return for high side gate driver. Must be connected to the source of the

high-side half bridge power switch.

ﬂoating supply

A buffer capacitor must be connected between this pin and the SH pin. This

capacitor is charged when the low-side power switch is on and supplies the

high-side driver when the high-side power switch is on.

high-side driver output

Gate connection of the high-side half bridge power switch.

Table 3.

Pin description …continued

Symbol

Description

Function

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