AAT2856_08 Datasheet, PDF (2/18 Pages) Advanced Analogic Technologies – High Current Charge Pump with Dual LDO for Backlight Applications

PRODUCT DATASHEET
AAT2856
ChargePump^TM High Current Charge Pump with Dual LDO for Backlight Applications
Pin Descriptions
Pin #
1
2
3
4, 5, 23, 24
6
7
8
9, 18
10
11
12
13
14, 21, 22
15
16
17
19
20
25
26
27
28
EP
Symbol
BL3
BL2
BL1
AGND
REF
FBB
OUTB
IN
FBA
OUTA
C1-
C1+
OUT
ENB
C2+
C2-
PGND
ENS
BL6
BL5
ENA
BL4
Description
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.
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.
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.
Analog ground. Connect AGND to PGND at a single point as close to the AAT2856 as possible.
Reference output. Bypass REF to AGND with a 0.1μF or larger ceramic capacitor.
Feedback input for LDO B. FBB measures the output voltage of LDO B. Connect a resistive voltage di-
vider from the output of LDO B to FBB. FBB feedback regulation voltage is 1.2V.
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.
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.
Feedback input for LDO A. FBA measures the output voltage of LDO A. Connect a resistive voltage di-
vider from the output of LDO A to FBA. FBA feedback regulation voltage is 1.2V.
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.
Negative node of charge pump capacitor 1. Connect the 1μF charge pump capacitor 1 from C1+ to C1-.
Positive node of charge pump capacitor 1. Connect the 1μF charge pump capacitor 1 from C1+ to C1-.
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.
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.
Positive node of charge pump capacitor 2. Connect the 1μF charge pump capacitor 2 from C2+ to C2-.
Negative node of charge pump capacitor 2. Connect the 1μF charge pump capacitor 2 from C2+ to C2-.
Power ground. Connect AGND to PGND at a single point as close to the AAT2856 as possible.
Backlight enable and serial control input. ENS turns the backlight on/off and is the AS²Cwire input to
serially control the backlightLED brightness.
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.
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.
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.
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.
Exposed paddle (bottom); connect to ground as closely as possible to the device.
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2856.2008.02.1.3