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PDF AAT3123A Data sheet ( Hoja de datos )
| Número de pieza | AAT3123A | |
| Descripción | High Efficiency 1X/1.5X Fractional Charge Pump | |
| Fabricantes | AAT | |
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AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
General Description
Features
ChargePump™
The AAT3123/23A/24 is a low noise, constant fre-
quency charge pump DC/DC converter that uses a
• VIN Range: 2.7V to 5.5V
• Dual Mode 1X and 1.5X Charge Pump for
dual mode load switch (1X) and fractional (1.5X)
Maximum Efficiency
conversion to maximize efficiency for white LED
applications. The device can be used to produce
• Drives Low-VF and High-VF Type LEDs
• Up to Six 20mA Outputs (AAT3124)
current levels up to 20mA to drive up to six LEDs
• Up to Four 20mA Outputs (AAT3123/23A)
from a 2.7V to 5.5V input. Outputs may be operat-
• 32-Position Logarithmic Scale with Digital
ed individually or paralleled for driving higher-cur-
Control
rent LEDs. A low external parts count (two 1µF fly-
• Simple Serial Control (S2Cwire) Interface
ing capacitors and two small 1µF capacitors at VIN
and OUT) make the AAT3123/23A/24 ideally suited
• Low Noise Constant Frequency Operation
• 1MHz Switching Frequency
for small battery-powered applications.
• Small Application Circuit
AnalogicTech’s Simple Serial Control™ (S2Cwire™)
interface is used to enable, disable, and set the
LED drive current with a 32-level logarithmic scale
LED brightness control. The AAT3123/23A/24 has a
thermal management system to protect the device
in the event of a short-circuit condition at the output
pin. Built-in soft-start circuitry prevents excessive
• Regulated Output Current
• Automatic Soft Start
• No Inductors
• IQ <1µA in Shutdown
• Temperature Range: -40°C to +85°C
• 12-Pin TSOPJW Package (AAT3123/23A)
• 16-Pin 4x4mm QFN Package (AAT3124)
inrush current during start-up. A high charge pump
switching frequency enables the use of very small
external capacitors. A low-current shutdown featurewww.DataSheet4U.com
disconnects the load from VIN and reduces quies-
Applications
cent current to less than 1µA. The device also inte-
grates a test current/auto-disable feature for each
• Color (RGB) Lighting
channel. The AAT3123/23A is available in a very
• Programmable Current Source
small, Pb-free 12-pin TSOPJW package. The six
• White LED Backlighting
output AAT3124 is available in a Pb-free 16-pin
• White Photo Flash for DSCs
4x4mm QFN package.
Typical Application
VBATTERY
VIN C1+
CIN COUT
1µF 1µF
EN/SET
VOUT
C1-
C2+
AAT3124
C2-
EN/SET
GND
D1
D2
D3
D4
D5
D6
C1
1µF
C2
1µF
D6 D5 D4 D3 D2 D1
3123.2005.12.1.4
1
1 page  
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C.
Efficiency vs. Input Voltage
(4x20mA)
100
95
90
VDIODE = 3.2V
VDIODE = 3.4V
85
VDIODE = 3.0V
80
75
70
65
60
55
50
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1
Input Voltage (V)
Efficiency vs. Input Voltage
(4x10mA)
100
95
90
VDIODE = 3.2V
VDIODE = 3.4V
85
80 VDIODE = 3.0V
75
70
65
60
55
50
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1
Input Voltage (V)
IDIODE vs. Input Voltage
(4x20mA)
85
VDIODE = 3.2V
VDIODE = 3.4V
80
75 VDIODE = 3.0V
70
65
60
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1
Input Voltage (V)
IDIODE vs. Input Voltage
(4x10mA)
45
VDIODE = 3.2V
VDIODE = 3.4V
40
VDIODE = 3.0V
35
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1
Input Voltage (V)
Quiescent Current vs. Input Voltage
VIH and VIL vs. VIN
2.6 0.850
2.4
2.2
0.825
2.0 0.800
1.8
1.6
0.775
0.750
VIH
1.4
1.2
1.0
VDIODE = 3.4V
0.725
0.700
VIL
0.8
0.6 VDIODE = 3.0V
0.4
VDIODE = 3.2V
0.675
0.650
0.2 0.625
0.0 0.600
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1
2.5 3.0 3.5 4.0 4.5 5.0 5.5
Input Voltage (V)
Input Voltage (V)
3123.2005.12.1.4
5
5 Page 
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
For a charge pump with an output of 5 volts and a
nominal input of 3.5 volts, the theoretical efficiency
is 95%. Due to internal switching losses and IC
quiescent current consumption, the actual efficien-
cy can be measured at 93%. These figures are in
close agreement for output load conditions from
1mA to 100mA. Efficiency will decrease as load
current drops below 0.05mA or when the level of
VIN approaches VOUT. Refer to the Typical
Characteristics section of this datasheet for meas-
ured plots of efficiency versus input voltage and
output load current for the given charge pump out-
put voltage options.
Capacitor Selection
Careful selection of the four external capacitors
CIN, C1, C2, and COUT is important because they will
affect turn-on time, output ripple, and transient per-
formance. Optimum performance will be obtained
when low equivalent series resistance (ESR)
ceramic capacitors are used. In general, low ESR
may be defined as less than 100mΩ. A value of
1µF for all four capacitors is a good starting point
when choosing capacitors. If the LED current
sources are only programmed for light current lev-
els, then the capacitor size may be decreased.
Capacitor Characteristics
Ceramic composition capacitors are highly recom-
mended over all other types of capacitors for use
with the AAT3123/23A/24. Ceramic capacitors
offer many advantages over their tantalum and alu-
minum electrolytic counterparts. A ceramic capac-
itor typically has very low ESR, is lowest cost, has
a smaller PCB footprint, and is non-polarized. Low
ESR ceramic capacitors help to maximize charge
pump transient response. Since ceramic capaci-
tors are non-polarized, they are not prone to incor-
rect connection damage.
Equivalent Series Resistance
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal
to a capacitor that is caused by the leads, internal
connections, size or area, material composition,
and ambient temperature. Capacitor ESR is typi-
cally measured in milliohms for ceramic capacitors
and can range to more than several ohms for tanta-
lum or aluminum electrolytic capacitors.
3123.2005.12.1.4
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1µF are typically
made from NPO or C0G materials. NPO and C0G
materials typically have tight tolerance and are sta-
ble over temperature. Large capacitor values are
typically composed of X7R, X5R, Z5U, or Y5V
dielectric materials. Large ceramic capacitors, typ-
ically greater than 2.2µF, are often available in low-
cost Y5V and Z5U dielectrics, but capacitors
greater than 1µF are typically not required for
AAT3123/23A/24 applications.
Capacitor area is another contributor to ESR.
Capacitors that are physically large will have a lower
ESR when compared to an equivalent material
smaller capacitor. These larger devices can improve
circuit transient response when compared to an
equal value capacitor in a smaller package size.
Test Current/Channel Disable
Each channel of the output is equipped with test
current function. A small amount of current (~2µA)
is injected into each output current source to detect
the presence of load (LED). Unused channels that
are tied to ground or LED load fail short will be
automatically disabled instead of wasting the pro-
grammed output current. The test current in the
AAT3123A is higher (~150µA) to accommodate
LEDs with lower impedance in failure mode.
Thermal Protection
The AAT3123/23A/24 has a thermal protection circuit
that will shut down the internal LDO and charge pump
if the die temperature rises above the thermal limit, as
is the case during a short-circuit of the OUT pin.
Driving Multiple LEDs, White LED
Display Module Backlights, and
Individual LEDs Connected in Parallel
The AAT3123/23A/24 D1 to D6 outputs are true
constant current sources capable of driving up to
20mA each over the operation input voltage range.
Since these outputs are true constant current
sources, they may be connected in parallel to drive
a single power output. Any combination of outputs
(D1 to D6) may be connected in parallel. The max-
imum total output current is a sum of how many
current sources are parallel connected. This fea-
ture is particularly useful to power pre-manufac-
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AAT3123A.PDF ] | |
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