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PDF AAT2856 Data sheet ( Hoja de datos )
| Número de pieza | AAT2856 | |
| Descripción | High Current Charge Pump | |
| Fabricantes | AAT | |
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AAT2856
High Current Charge Pump with
Dual LDO for BacklightApplications
General Description
Features
ChargePump™
www.DataSheet4U.com
The AAT2856 is a highly integrated charge pump
with dual linear regulators optimized for systems
powered from lithium-ion/polymer batteries. The
charge pump provides power for white LED back-
light. Six backlight LEDs can be driven at up to
30mA. AnalogicTech's AS2Cwire™ (Advanced
Simple Serial Control™) single-wire interface is used
to enable, disable, and set the current to one of 32
levels for the backlight. Backlight current matching is
1% for uniform display brightness.
The AAT2856 offers two high-performance low-
noise MicroPower™ low dropout (LDO) linear regu-
lators. Both regulators use individual enable inputs
and each will supply up to 200mA load current. LDO
ground pin current is only 80µA, making the
AAT2856 ideal for battery-operated applications.
The AAT2856 is equipped with built-in short-circuit
and over-temperature protection. The soft start cir-
cuitry prevents excessive inrush current at start-up
and mode transitions.
The AAT2856 is available in a Pb-free TQFN44-28
package and operates over the -40°C to +85°C
ambient temperature range.
• Input Voltage Range: 2.7V to 5.5V
• Tri-Mode Charge Pump:
— Drives up to Six Backlight LEDs
— 32 Programmable Backlight Current
Settings Ranging from 115µA to 30mA
— 2MHz Switching Frequency
• Two Linear Regulators:
— 200mA Output Current
— 200mV Dropout Voltage
— Output Voltage Adjustable from 1.2V to
VBATTERY
— Output Auto-Discharge for Fast Shutdown
— Individual LDO Enable Inputs
• Built-In Thermal Protection
• Automatic Soft Start
• -40°C to +85°C Temperature Range
• TQFN44-28 Package
Applications
• Camera-Enabled Mobile Devices
• Digital Still Cameras
• Multimedia Mobile Phones
Typical Application
VBAT
CIN
4.7μF
ENABLE/SET
CBYP
0.1μF
C1 C2
1μF 1μF
C1+ C1-
IN
C2+ C2-
OUT
IN
AAT2856
ENS
BL1
BL2
BL3
BL4
BL5
BL6
REF
OUTA
FBA
COUT
2.2μF
VOUT
WLEDs
OSRAM LW M673
or equivalent
VOUTA
R2A
COUTA
R1A 2.2μF
EN_LDOA
EN_LDOB
ENA
ENB
AGND
OUTB
FBB
PGND
VOUTB
R2B
COUTB
R1B 2.2μF
2856.2007.06.1.0
1
1 page  
AAT2856
High Current Charge Pump with
Dual LDO for BacklightApplications
Electrical Characteristics1, 2
VIN = 3.6V; CIN = 4.7µF; COUT = 2.2µF; C1 = C2 = 1µF; TA = -40°C to +85°C, unless otherwise noted. Typical
values are TA = 25°C.
Symbol Description
VIN IN Operating Voltage Range
IIN(Q)
IN Operating Current
IIN(SHDN)
TSD
IN Shutdown Current
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
TSD(HYS) Hysteresis
Charge Pump Section
IOUT
VIN(TH_H)
fOSC
OUT Maximum Output Current
Charge Pump Mode Hysteresis
Charge Pump Oscillator
Frequency
BL1-BL6 Backlight LED Outputs
IBL_(MAX) BL1-BL6 Maximum Current
ΔI(BL_)
VBL_(TH)
BL1-BL6 Current Matching2
BL1-BL6 Charge Pump Mode
Transition Threshold
ENS Logic Control
VENS(L)
VENS(H)
IENS
tENS(LOW)
tENS(HI_MIN),
tENS(HI_MIN)
tENS(HI_MAX),
tENS(HI_MAX)
tENS(OFF)
tENS(LAT)
ENS Input Low Threshold
ENS Input High Threshold
ENS Input Leakage Current
ENS Serial Interface Low Time
ENS Serial Interface Minimum
High Time
ENS Serial Interface Maximum
High Time
ENS Off Timeout
ENS Serial Interface Latch
Timeout
Conditions
1X Mode, 3.0V ≤ VIN ≤ 5.5V, Active,
No Load; ENL = AGND, ENS = IN
1.5X Mode, 3.0V ≤ VIN ≤ 5.5V, Active,
No Load; ENL = AGND, ENS = IN
2X Mode, 3.0V ≤ VIN ≤ 5.5V, Active,
No Load; ENL = AGND, ENS = IN
ENA = ENB = ENS = AGND
Address 0, Data 1
TA = 25°C
Address 0, Data 1; VIN - VF = 1.5V
Address 12, Data 2; VIN - VF = 1.5V
Address 0, Data 1; VIN - VF = 1.5V
VENS = VIN = 5V
VIN ≥ 3.3V
VIN ≥ 3.3V
Min Typ Max Units
2.7 5.5 V
1
4 mA
5
1.0
140
µA
°C
15 °C
200 mA
500 mV
2 MHz
18 20 22 mA
30
1.0 %
150 mV
0.4 V
1.4 V
-1.0 1.0 µA
0.3 75 µs
50 ns
75 µs
500 µs
500 µs
1. The AAT2856 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. Current matching is defined as the deviation of any sink current from the average of all active channels.
2856.2007.06.1.0
5
5 Page 
AAT2856
High Current Charge Pump with
Dual LDO for BacklightApplications
scales and the maximum current level is fixed at
20mA or 30mA, depending on the scale chosen
through programming.
If any one of the backlight or flash current sinks is
not used, connect that current sink to OUT. The
current controller monitors the sink voltage and, if it
is connected to OUT, then the controller deter-
mines that the current sink is not used or that the
LED is shorted. In either case, the controller turns
off the affected current sink.
AS2Cwire Serial Interface
The AAT2856 is dynamically programmable by the
AS2Cwire single-wire interface. AS2Cwire records
rising edges detected at the ENS pin to address
and load the data registers. AS2Cwire latches data
or address after the ENS input has been held high
for time tLAT (500µs). Address or data is differenti-
ated by the number of ENS rising edges. Since the
data registers are 4 bits each, the differentiating
number of pulses is 24 or 16, so that Address 0 is
identified by 17 rising edges, Address 1 by 18 ris-
ing edges, Address 2 by 19 rising edges, etc. Data
is set to any number of rising edges between 1 and
16. A typical write protocol is a burst of ENS rising
edges identifying a particular address, followed by
a pause with ENS held high for the tLAT timeout
period, then a burst of rising edges signifying data,
and another tLAT timeout after the data has been
sent. Once an address is set, multiple writes to that
address are allowed since the address is not reset
after each write. Address edges are needed when
changing the address, or writing to an address
other than the default after shutdown. Address 0 is
the default address after shutdown. If the part is
enabled with only data edges and no address, then
Address 0 will be programmed and backlight chan-
nels BL1-BL6 will turn-on according to the number
of data edges applied.
When ENS is held low for a time longer than tOFF
(500µs), the AAT2856 enters shutdown mode and
draws less than 1µA of current from IN. At shut-
down, the data and address registers are reset to 0.
2856.2007.06.1.0
AS2Cwire Serial Interface Addressing
Address
0
1
2
3
12
15
Sub-2
Sub-3
ENS
Rising
Edges
17
18
19
20
29
32
19
20
Function
Backlight Current BL1-BL6
Main Backlight Current
BL1-BL5
Sub Backlight Current BL6
Low Current Backlight
Maximum Backlight Current
(Main and Sub)
Backlight Independent
Control
BL3-BL6 On/Off Control
BL1/BL2 On/Off Control
Table 1: AS2Cwire Serial Interface Addressing.
Backlight Current Control (Address 0-3)
Use Addresses 0-3 to program all six backlight LED
channels. All six backlight channels are pro-
grammed to the same current level by writing
Address 0 followed by any Data between 1 and 16.
To program only the main channels BL1 through
BL5, use Address 1. Similarly, use Address 2 to
program only the sub channel BL6 independently.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
30mA Max (mA)
30.0
27.9
26.1
24.2
21.0
19.2
17.3
15.0
12.7
10.9
8.1
6.2
4.4
3.5
2.6
0
20mA Max (mA)
20.0
19.0
17.8
16.5
14.3
13.0
11.8
10.2
8.5
7.3
5.4
4.1
2.9
2.2
1.6
0
Table 2: Data for the Backlight Current Level
(Address 0-3).
11
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| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet AAT2856.PDF ] | |
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