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PDF AAT3151 Data sheet ( Hoja de datos )
| Número de pieza | AAT3151 | |
| Descripción | High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
General Description
Features
ChargePump™
The AAT3151 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-mode
• VIN Range: 2.7V to 5.5V
• Fully Programmable Current with Single Wire
load switch (1X), fractional (1.5X), and doubling (2X)
• 16-Step Logarithmic Scale
conversion to maximize efficiency for white LED
• 15/20/30mA Max Current
applications. The AAT3151 is capable of driving
• Four Low Current Settings Down to 50µA
four-channel LEDs at a total of 120mA from a 2.7V
to 5.5V input. The current sinks may be operated
• Low IQ (40µA) for Low Current Mode
• Tri-Mode 1X, 1.5X, and 2X Charge Pump for
individually or in parallel for driving higher-current
LEDs. A low external parts count (two 1µF flying
Maximum Efficiency and VF Coverage
• Drives Four Channels of LEDs
capacitors and two small 1µF capacitors at VIN and
VOUT) makes the AAT3151 ideally suited for small
battery-powered applications.
• Individual Main/Sub-Group Control
• No Inductors, Low Noise Operation
• 1MHz Constant Switching Frequency
AnalogicTech's AS2Cwire™ (Advanced Simple
Serial Control™) serial digital input is used to
enable, disable, and set current for each LED with
a 16-level logarithmic scale plus four low-current
settings down to 50µA for optimized efficiency, with
a low housekeeping current of only 40µA.
• Small Application Circuit
• Built-In Thermal Protection
• Built-In Auto-Disable for Short-Circuit
• Automatic Soft-Start
• IQ <1µA in Shutdown
• Thermally Enhanced 3x3mm 12-Pin DFN
Package
Each output of the AAT3151 is equipped with built-
in protection for VOUT short-circuit and auto-disable
for LED failure condition. Built-in soft-start circuitry
www.DataSheet4U.comprevents excessive inrush current during start-up.
A low-current shutdown feature disconnects the
Applications
load from VIN and reduces quiescent current to less
than 1µA.
• Color (RGB) Lighting
• Programmable Current Sinks
The AAT3151 is available in a space-saving, ther-
• White LED Backlighting
mally-enhanced, 12-pin 3x3mm DFN package.
• White Photo-Flash for DSCs
Typical Application
2.7V to 5.5V
VIN C1+
CIN
1µF C1-
C2+
AAT3151
C2-
VOUT
EN/SET
EN/SET
GND
D1
D2
D3
D4
C1
1µF
C2
1µF
D1 D2 D3 D4
COUT
1µF
3151.2004.10.0.6
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AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
Efficiency vs. Supply Voltage
100
90
80
70
60
50
2.8
4.1mA
10.2mA
20mA
3.0 3.2 3.4 3.6 3.8 4.0 4.2
Supply Voltage (V)
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(100mA/div)
Turn On to 1X Mode
VIN = 4.2V, DX = 20mA
100µs/div
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(100mA/div)
Turn On to 1.5X Mode
VIN = 3.5V, DX = 20mA
Turn On to 2X Mode
VIN = 2.8V, DX = 20mA
EN
www.DataShee(2Vt/d4CivP) U.com
(2V/div)
VSINK
(500mV/div)
IIN
(100mA/div)
100µs/div
100µs/div
EN
(2V/div)
VF
(1V/div)
IIN
(200mA/div)
Turn Off from 1.5X Mode
VIN = 3.5V, DX = 20mA
200µs/div
3151.2004.10.0.6
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AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
For a charge pump with an output of 5 volts and a
ceramic capacitors help maximize charge pump
nominal input of 3.5 volts, the theoretical efficiency
transient response. Since ceramic capacitors are
is 95%. Due to internal switching losses and IC
non-polarized, they are not prone to incorrect con-
quiescent current consumption, the actual efficien-
nection damage.
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 level of VIN
approaches VOUT.
Equivalent Series Resistance
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal
to a capacitor, which is caused by the leads, inter-
Capacitor Selection
nal connections, size or area, material composition,
and ambient temperature. Capacitor ESR is typi-
Careful selection of the four external capacitors
cally measured in milliohms for ceramic capacitors
CIN, C1, C2, and COUT is important because they
will affect turn-on time, output ripple, and transient
and can range to more than several ohms for tanta-
lum or aluminum electrolytic capacitors.
performance. Optimum performance will be
obtained when low equivalent series resistance
(ESR) (<100mΩ) ceramic capacitors are used. In
Ceramic Capacitor Materials
general, low ESR may be defined as less than
Ceramic capacitors less than 0.1µF are typically
100mΩ. A capacitor value of 1µF for all four capac-
made from NPO or COG materials. NPO and COG
itors is a good starting point when choosing capac-
materials typically have tight tolerance and are sta-
itors. If the constant current sinks are only pro-
ble over temperature. Larger capacitor values are
grammed for light current levels, then the capacitor
typically composed of X7R, X5R, Z5U, or Y5V
www.DataSheet4U.comsize may be decreased.
dielectric materials. Large ceramic capacitors, typ-
ically greater than 2.2µF, are often available in low-
cost Y5V and Z5U dielectrics, but capacitors
Capacitor Characteristics
greater than 1µF are typically not required for
Ceramic composition capacitors are highly recom-
AAT3151 applications.
mended over all other types of capacitors for use
with the AAT3151. Ceramic capacitors offer many
advantages over their tantalum and aluminum elec-
trolytic counterparts. A ceramic capacitor typically
has very low ESR, is lowest cost, has a smaller
PCB footprint, and is non-polarized. Low ESR
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.
3151.2004.10.0.6
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| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet AAT3151.PDF ] | |
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