AAT2856

High Current Charge Pump with

Dual LDO for BacklightApplications

2

2856.2007.06.1.0

Pin Descriptions

Pin #

Symbol

Description

1

BL3

Backlight LED 3 current sink. BL3 controls the current through backlight LED 3. Connect

the cathode of backlight LED 3 to BL3. If not used, connect BL3 to OUT.

2

BL2

Backlight LED 2 current sink. BL2 controls the current through backlight LED 2. Connect

the cathode of backlight LED 2 to BL2. If not used, connect BL2 to OUT.

3

BL1

Backlight LED 1 current sink. BL1 controls the current through backlight LED 1. Connect

the cathode of backlight LED 1 to BL1. If not used, connect BL1 to OUT.

4, 5, 23, 24

AGND

Analog ground. Connect AGND to PGND at a single point as close to the AAT2856 as

possible.

6

REF

Reference output. Bypass REF to AGND with a 0.1µF or larger ceramic capacitor.

7

FBB

Feedback input for LDO B. FBB measures the output voltage of LDO B. Connect a resistive

voltage divider from the output of LDO B to FBB. FBB feedback regulation voltage is 1.2V.

8

OUTB

LDO B regulated voltage output. OUTB is the voltage output of LDO B. Bypass OUTB to

AGND with a 2.2µF or larger ceramic capacitor as close to the AAT2856 as possible.

9, 18

IN

Power input. Connect IN to the input source voltage. Bypass IN to PGND with a 4.7µF or

larger ceramic capacitor as close to the AAT2856 as possible.

10

FBA

Feedback input for LDO A. FBA measures the output voltage of LDO A. Connect a resistive

voltage divider from the output of LDO A to FBA. FBA feedback regulation voltage is 1.2V.

11

OUTA

LDO A regulated voltage output. OUTA is the voltage output of LDO A. Bypass OUTA to

AGND with a 2.2µF or larger ceramic capacitor as close to the AAT2856 as possible.

12

C1-

Negative node of charge pump capacitor 1. Connect the 1µF charge pump capacitor 1

from C1+ to C1-.

13

C1+

Positive node of charge pump capacitor 1. Connect the 1µF charge pump capacitor 1 from

C1+ to C1-.

14, 21, 22

OUT

Charge pump output; supplies current to the backlight LEDs. Connect the backlight LED

anodes to OUT. Bypass OUT to PGND with a 2.2µF or larger ceramic capacitor as close

to the AAT2856 as possible.

15

ENB

LDO B enable input. ENB turns on or off low dropout regulator B (LDO B). Drive ENB high

to turn on LDO B; drive it low to turn it off.

16

C2+

Positive node of charge pump capacitor 2. Connect the 1µF charge pump capacitor 2 from

C2+ to C2-.

17

C2-

Negative node of charge pump capacitor 2. Connect the 1µF charge pump capacitor 2

from C2+ to C2-.

19

PGND

Power ground. Connect AGND to PGND at a single point as close to the AAT2856 as pos-

sible.

20

ENS

Backlight enable and serial control input. ENS turns the backlight on/off and is the

AS

25

BL6

Backlight LED 6 current sink. BL6 controls the current through backlight LED 6. Connect

the cathode of backlight LED 6 to BL6. If not used, connect BL6 to OUT.

26

BL5

Backlight LED 5 current sink. BL5 controls the current through backlight LED 5. Connect

the cathode of backlight LED 5 to BL5. If not used, connect BL5 to OUT.

27

ENA

LDO A enable input. ENA turns on or off low dropout regulator A (LDO A). Drive ENA high

to turn on LDO A; drive low to turn it off.

28

BL4

Backlight LED 4 current sink. BL4 controls the current through backlight LED 4. Connect

the cathode of backlight LED 4 to BL4. If not used, connect BL4 to OUT.

EP

Exposed paddle (bottom); connect to ground as closely as possible to the device.