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PDF AAT3164 Data sheet ( Hoja de datos )
| Número de pieza | AAT3164 | |
| Descripción | High Efficiency 1X/1.5X/2X Charge Pump | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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AAT3164
High Efficiency 1X/1.5X/2X Charge Pump for
Six-Channel White LED Applications
General Description
Features
ChargePump™
The AAT3164 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-
mode load switch (1X), fractional (1.5X), and dou-
bling (2X) conversion to maximize efficiency for
white LED applications. The device is capable of
driving up to six channels of LEDs at up to 30mA
per channel from a 2.7V to 5.5V input. The current
sinks may be operated individually or in parallel for
driving higher-current LEDs. A low external parts
count (two 1µF flying capacitors and two small 1µF
capacitors at IN and OUT) makes this part ideally
suited for small, battery-powered applications.
AnalogicTech's patented single-wire Simple Serial
Control™ (S2Cwire™) serial digital input is used to
enable, disable, and set current for each LED with
16 levels from a maximum of 40mA down to 50µA.
The maximum current level is programmed via an
external resistor. To save power, the low-current
mode supply current can be programmed as low
as 70µA.
Each output of the AAT3164 is equipped with built-
in protection for VOUT short-circuit and auto-disable
for LED short-circuit conditions. Built-in soft-start
circuitry prevents excessive inrush current during
start-up. A low-current shutdown feature discon-
nects the load from VIN and reduces quiescent cur-
rent to less than 1µA.
The AAT3164 is available in a Pb-free, space-saving,
ultra-thin (3x4x0.75mm), thermally-enhanced 16-pin
TDFN package.
• VIN Range: 2.7V to 5.5V
• Tri-Mode (1X/1.5X/2X) Charge Pump Operation
— Maximizes Efficiency and LED VF
Coverage
— 1MHz Constant Switching Frequency
— No Inductors, Low Noise Operation
• Drives Six Channels of LEDs up to 30mA/
Channel
— User-Programmable RSET Sets Maximum
LED Current
— Excellent LED Channel-to-Channel
Current Match
• Digitally Programmable LED Current with
Single-Wire S2Cwire Interface
— 16 Current Levels From ILED_MAX to 50µA
• Low IQ (70µA) for Low Current Mode Operation
• True Load Disconnect in Shutdown; IQ < 1µA
• Built-In Thermal Protection
• Built-In Auto-Disable for Open LED Circuit
• Automatic Soft-Start Minimizes Inrush Startup
Current
• Small 3x4mm TDFN34-16 Package
Applications
• Color (RGB) Lighting
• Programmable Current Sinks
• White LED Backlighting
• White Photo Flash for Digital Still Cameras
Typical Application
Li-Ion
Battery
VNOM = 3.6V
CIN
1µF
EN/SET
26.1K
1%
1µF 1µF
C1+ C1- C2+ C2-
IN OUT
AAT 3164
GND
EN/SET
RSET
D1
D2
D3
D4
D5
D6
COUT
D1 D2 D3 D4 D5 D6
1µF
OSRAM
LW M67C
3164.2006.07.1.0
1
Free Datasheet http://www.datasheet4u.com/
1 page  
AAT3164
High Efficiency 1X/1.5X/2X Charge Pump for
Six-Channel White LED Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1.0µF; TA = 25°C, RSET = 26.1kΩ, VIN = 3.6V, unless otherwise noted.
Efficiency vs. Supply Voltage
100
90
80
70
60
50
2.8
5.0mA/ch
VF = 2.9V
10.2mA/ch
VF = 3.1V
20mA/ch
VF = 3.4V
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
(200mA/div)
Turn-On to 1X Mode
(VIN = 4.2V; 20mA/Channel; Data 1)
Time (100µs/div)
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 1.5X Mode
(VIN = 3.8V; 20mA/Channel; Data 1)
Time (100µs/div)
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 2X Mode
(VIN = 2.8V; 20mA/Channel; Data 1)
Time (100µs/div)
EN
(2V/div)
VF
(1V/div)
IIN
(100mA/div)
Turn-Off from 1.5X Mode
(VIN = 3.5V; 20mA/Channel; Data 1)
Time (100µs/div)
Current Matching vs. Temperature
20.2
20.0
19.8
19.6
19.4
19.2
-40
Channel 2
Channel 1
Channel 5
Channel 3
Channel 4
Channel 6
-20 0 20 40 60 80
Temperature (°C)
3164.2006.07.1.0
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
AAT3164
High Efficiency 1X/1.5X/2X Charge Pump for
Six-Channel White LED Applications
Additionally, a digital-to-analog converter can be
used with the RSET pin to control the brightness
level. The result is like the equation above, where
VIO is replaced with VDAC:
ILED(LO)
=
870
⎛ 0.6
⎝R1 // R2
-
VDAC⎞
R2 ⎠
For cases where PWM dimming is preferred, the
PWM signal can be applied directly to the RSET resis-
tor, as shown in Figure 4. In order for the LED current
to go to zero, the voltage level of the PWM signal
must exceed the RSET pin voltage level of 0.6V.
PWM
R1
AAT 3164
RSET
Figure 4: RSET Configuration for PWM
Dimming Control.
Device Power Efficiency
The AAT3164 power conversion efficiency
depends on the charge pump mode. By definition,
device efficiency is expressed as the output power
delivered to the LEDs divided by the total input
power consumed.
η
=
POUT
PIN
When the input voltage is sufficiently greater than
the LED forward voltages, the device optimizes
efficiency by operating in 1X mode. In 1X mode,
the device is working as a bypass switch and pass-
ing the input supply directly to the output. By sim-
plifying the conditions such that the LEDs have uni-
form VF, the power conversion efficiency can be
approximated by:
η=
VF · ILED
VIN · IIN
≈
VF
VIN
3164.2006.07.1.0
Due to the very low 1X mode quiescent current, the
input current nearly equals the total output current
delivered to the LEDs. Further, the low resistance
bypass switch introduces negligible voltage drop
from input to output.
The AAT3164 further maintains optimized perform-
ance and efficiency by detecting when the input
voltage is not sufficient to sustain LED drive cur-
rent. The device automatically switches to 1.5X
mode when the input voltage drops too low in rela-
tion to the LED forward voltages.
In 1.5X mode, the output voltage can be boosted to
3/2 the input voltage. The 3/2 conversion ratio
introduces a corresponding 1/2 increase in input
current. For ideal conversion, the 1.5X mode effi-
ciency is given by:
η=
VF · ILED
VIN · 1.5IIN
≈
VF
1.5 · VIN
Similarly, when the input falls further, such that
1.5X mode can no longer sustain LED drive cur-
rent, the device will automatically switch to 2X
mode. In 2X mode, the output voltage can be
boosted to twice the input voltage. The doubling
conversion ratio introduces a corresponding dou-
bling of the input current. For ideal conversion, the
2X mode efficiency is given by:
η=
VF · ILED
VIN · 2IIN
≈
VF
2 · VIN
Additional Applications
The current sinks of the AAT3164 can be combined
to drive higher current levels through a single LED.
As an example, each LED of a three-die arrange-
ment can be driven at 80mA each, or 240mA total
(see Figure 5).
Other applications that require constant current
can also be accommodated by combining constant
current channels to achieve the necessary current
levels.
11
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11 Page | ||
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