AAT2846 Datasheet, PDF (2/25 Pages) Advanced Analogic Technologies – High Current Charge Pump with Dual LDO for Backlight and Flash Applications

AAT2846
High Current Charge Pump with Dual LDO
for Backlight and Flash Applications
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9, 18
10
11
12
13
14
15
16
17
19
20
21
22
Symbol
BL3
BL2
BL1
AGND
CT
REF
FBB
OUTB
IN
FBA
OUTA
C1-
C1+
OUT
ENB
C2+
C2-
PGND
ENS
FL2
FL1
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 AAT2846 as possible.
Flash timer control capacitor input. Connect a capacitor from CT to AGND to set the flash
timer. A 100nF capacitor sets the timer to 1 second.
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 divider 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 AAT2846 as possible.
Power input. Connect IN to the input source voltage. Bypass IN to PGND with a 4.7µF or larg-
er ceramic capacitor as close to the AAT2846 as possible.
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.
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 AAT2846 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 and flash LEDs. Connect the backlight
and flash LED anodes to OUT. Bypass OUT to PGND with a 2.2µF or larger ceramic capacitor
as close to the AAT2846 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 AAT2846 as possible.
Flash and backlight enable and serial control input. ENS turns on/off both the flash and back-
light and is the AS²Cwire input to serially control the backlight and movie-mode flash LED
brightness.
Flash LED 2 current sink. FL2 controls the current through flash LED 2. Connect the cathode
of flash LED 2 to FL2. If not used, connect FL2 to OUT.
Flash LED 1 current sink. FL1 controls the current through flash LED 1. Connect the cathode
of flash LED 1 to FL1. If not used, connect FL1 to OUT.
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2846.2007.08.1.0