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PDF AAT2806 Data sheet ( Hoja de datos )
| Número de pieza | AAT2806 | |
| Descripción | Dual High Efficiency Charge Pump | |
| Fabricantes | ANALOGIC TECH | |
| Logotipo |  |
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AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
General Description
Features
ChargePump™
The AAT2806 is a dual charge pump designed to
support both the white LED backlight and flash appli-
• VIN Range: 2.7V to 5.5V
• Dual Charge Pump to Support Backlight and
cations for systems operating with lithium-ion/poly-
Flash LEDs
mer batteries. The backlight charge pump is capable
• Backlight Charge Pump:
of driving up to four LEDs at a total of 80mA. The cur-
— Regulated Current
rent sinks may be operated individually or in parallel
— Four Current Sink Inputs
for driving higher current LEDs. To maximize power
— S2Cwire Brightness Control
efficiency, the charge pump operates in 1X, 1.5X, or
— Tri-Mode Charge Pump
2X mode, where the mode of operation is automati-
— Maximum 20mA of Current Per Input
cally selected by comparing the forward voltage of
each LED with the input voltage. AnalogicTech's
— Low IQ (50µA) in Light Load Mode
• Flash Charge Pump:
S2Cwire™ (Simple Serial Control™) serial digital
— Regulated Output Voltage
input is used to enable, disable, and set current for
— Up to 250mA of Pulsed Current
each LED with an 8-level logarithmic scale plus four
• Independent Backlight/Flash Control
low-current settings down to 50µA for optimized effi-
• Low Noise 1MHz Constant Frequency
ciency, with a typical operating quiescent current of
Operation
less than 50µA.
• Automatic Soft-Start
The flash charge pump is a charge pump doubler
with a regulated output voltage. It is designed to
• No Inductors
• Available in TDFN44-16 Package
deliver 120mA of continuous current and up to
250mA of pulsed current. It has an independent
enable pin for improved power savings.
www.DataSheet4U.com
The AAT2806 has thermal protection and built-in
Applications
soft-start circuitry. A low-current shutdown feature
disconnects the load from VIN and reduces quiescent
current to less than 1µA.
• Color (RGB) Lighting
• White LED Backlighting
• White LED Photo Flash
The AAT2806 is available in a space-saving, ther-
mally-enhanced TDFN44-16 package and is rated
over the -40°C to +85°C temperature range.
Typical Application
VIN CIN
1µF
EN/SET
EN_FLSH
C1 C2 C3
1µF 1µF 1µF
C1+ C1- C2+ C2- C3+ C3-
VOUT_FL
VIN
AAT2806
VOUT_BL
EN/SET
EN_FLSH
GND
D1
D2
D3
D4
VOUT_FLASH
COUT
1µF
Flash
Backlight
D1 D2 D3 D4
COUT
1µF
2806.2005.07.1.4
1
1 page  
AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
Typical Characteristics–Flash Driver Charge Pump Section
Output Voltage vs. Output Current
(VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND)
4.60
4.56
4.52 3.6V
4.48
4.44
4.40
0.1
3.0V 3.3V
2.7V
1.0
10.0
100.0
Output Current (mA)
1000.0
Maximum Current Pulse vs. Supply Voltage
(VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND)
450
One-shot pulse duration = 250ms
400 VOUT > 4.0V
350
300
250
200
150
100
50
0
3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
Supply Voltage (V)
EN_FLSH
(1V/div)
Startup Time
(50mA Load)
EN_FLSH
(1V/div)
Startup Time
(100mA Load)
VOUT_FL
(1V/div)
100µs/div
VOUT_FL
(1V/div)
100µs/div
Load Response vs. Time
(50mA Load)
VOUT_FL
(10mV/div)
VIN = 3.5V
IOUT
(20mA/div)
5ms/div
Load Response vs. Time
(100mA Load)
VIN = 3.5V
VOUT_FL
(10mV/div)
IOUT
(50mA/div)
5ms/div
2806.2005.07.1.4
5
5 Page 
AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
The flash charge pump is a charge pump doubler
with regulated output voltage. It is designed to deliv-
er 120mA of continuous current and 250mA of pulsed
current.
The AAT2806 requires six external components:
three 1µF ceramic capacitors for the charge pump
flying capacitors (C1, C2 and C3), one 1µF ceramic
input capacitor (CIN), one 0.33µF to 1µF ceramic
capacitor for backlight charge pump output capacitor
(COUT), and one 1µF ceramic capacitor for flash
charge pump output capacitor (COUT).
Constant Current Output Level Settings
The constant current level for the LED channels is set
via the S2Cwire serial interface (see Table 1).
Because the inputs D1 to D4 are true independent
constant current sinks, the voltage observed on any
single given input will be determined by the differ-
ence between VOUT and the actual forward voltage
(VF) of the LED being driven.
Since the constant current levels are programma-
ble, no PWM (pulse width modulation) or addition-
al control circuitry is needed to control LED bright-
ness. This feature greatly reduces the burden on a
microcontroller or system IC to manage LED or dis-
play brightness, allowing the user to "set it and for-
get it." With its high-speed serial interface (>1MHz
data rate), the LED current drive can be changed
successively to brighten or dim LEDs, in smooth
transitions (e.g., to fade-out) or in abrupt steps, giv-
ing the user complete programmability and real-
time control of LED brightness.
The AAT2806 offers an additional Low Current mode
with reduced quiescent current (Data 13-16). This
mode is especially useful for low-current applications
where a continuous, low current state is maintained.
The reduction in quiescent current significantly
reduces the impact due to maintaining a continuous
backlighting state.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
IOUT (mA)
D1-D3
Sub-Group D4
20 20
14 14
10 10
77
20 0
14 0
10 0
70
0 20
0 14
0 10
07
0.05 0.05
0.5 0.5
11
22
Table 1: Constant Current Programming Levels.
S2Cwire Serial Interface
The current sink input magnitude on the backlight
charge pump is controlled by AnalogicTech's
S2Cwire serial digital input. The interface relies on
the number of rising edges of the EN/SET pin to
address and load the registers. S2Cwire latches
data or address after the EN/SET pin has been
held high for time TLAT. The interface records rising
edges of the EN/SET pin and decodes them into 16
different states, as indicated in Table 1. There are
four brightness levels for the main or sub-display
group with the possibility of individually turning ON
or OFF each group. To further optimize power effi-
ciency, the device also offers four low-current lev-
els for dim LED operation (Data 13-16). During this
low-current mode, the internal supply current
reduces to only 50µA typical.
The counter can be clocked at speeds up to 1MHz,
such that intermediate states are not visible. The
first rising edge of EN/SET enables the IC and ini-
tially sets the output LED current to 20mA. Once
the final clock cycle is input for the desired bright-
ness level, the EN/SET pin is held high to maintain
the device output current at the programmed level.
The device is disabled 500µs (TOFF) after the
EN/SET pin transitions to a logic low state.
2806.2005.07.1.4
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AAT2806.PDF ] | |
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