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PDF AAT3195 Data sheet ( Hoja de datos )
| Número de pieza | AAT3195 | |
| Descripción | 4-Channel Charge-Pump LED Driver | |
| Fabricantes | AAT | |
| Logotipo |  |
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ChargePumpTM
General Description
The AAT3195 is a charge-pump based, current-sink
white LED driver capable of driving one to four LEDs up
to 30mA, each. It automatically switches between 1x
mode and 2x mode to maintain the highest efficiency
and optimal LED current accuracy and matching.
The AAT3195 charge pump’s 1x mode (bypass mode)
has very low resistance allowing LED current regulation
to be maintained with input supply voltage approaching
www.DatatShheeeLt4EUD.cofmorward voltage. The AAT3195 incorporates an
internal RSET and is available in a thermally enhanced,
Pb-free 2x2.1mm 10-lead SC70JW-10 package.
PRODUCT DATASHEET
AAT3195
4-Channel Charge-Pump LED Driver
Features
• Drives up to 4 LEDs at up to 30mA, each
• Automatic Switching Between 1x and 2x Modes
• 1MHz Switching Frequency
• Linear LED Output Current Control
▪ Single-wire, S2Cwire™ Interface
• AAT3195-1: 30mA, 32-step
• AAT3195-2: 20mA, 32-step
▪ ON/OFF or PWM Interface
• AAT3195-3
• ±10% LED Output Current Accuracy
• 3% LED Output Current Matching
• Low-current Shutdown Mode
• Built-in Thermal Protection
• Automatic Soft-start
• 2x2.1mm SC70JW-10 Package
Applications
• Cordless Phone Handsets
• Digital Cameras
• Mobile Phone Handsets
• MP3 and PMP Players
Typical Application
Input Voltage
2.7V to 5.5V
CIN
1µF
CP
1µF
EN/SET
S2Cwire
Interface
IN OUT
C+
AAT3195
C-
EN/SET
GND
D1
D2
D3
D4
COUT
1µF
WLEDs
3195.2008.09.1.0
www.analogictech.com
1
1 page  
ChargePumpTM
PRODUCT DATASHEET
AAT3195
4-Channel Charge-Pump LED Driver
Electrical Characteristics
IN = EN = 3.6V; CIN = 1 μF; COUT = 1μF; CCP = 1μF; TA=-40°C to 85°C unless otherwise noted. Typical values are at TA
= 25°C.
Symbol
Description
AAT3195-1/-2: EN/SET and S2Cwire Control
VEN(H)
EN Input High Threshold Voltage
VEN(L)
EN Input Low Threshold Voltage
IEN(LKG)
EN Input Leakage Current
www.DataSheet4tUEN.c/SoEmT(OFF)
tEN/SET(LAT)
EN/SET Input OFF Timeout
EN/SET Input Latch Timeout
tEN/SET(LOW)
EN/SET Input LOW Time
tENSET(H-MIN)
EN/SET Minimum High Time
tENSET(H-MAX)
EN/SET Maximum High Time
AAT3195-3: EN/PWM Current Control
VEN(H)
EN/PWM Input High Threshold Voltage
VEN(L)
EN/PWM Input Low Threshold Voltage
IEN(LKG)
EN/PWM Input Leakage Current
tPWM(ON)
PWM Control Turn-On Delay
tEN/PWM
EN/PWM Input OFF Timeout
fPWM PWM Control Frequency
Conditions
EN/SET ≥ VEN(H)
EN/PWM = IN = 5V
Duty Cycle = 80%
Min
1.4
-1
0.3
1.4
-1
0.15
Typ Max Units
0.4
1
500
500
75
50
75
V
V
μA
μs
μs
μs
ns
μs
V
0.4 V
1 μA
2 μs
1 ms
50 kHz
3195.2008.09.1.0
www.analogictech.com
5
5 Page 
ChargePumpTM
EN/PWM Duty Cycle
100%
90%
80%
70%
60%
50%
40%
30%
20%
www.DataSheet4U.com10%
D1-D3 Current (mA)
30
27
24
21
18
15
12
9
6
3
Table 2: AAT3195-3 LED Current Settings
PRODUCT DATASHEET
AAT3195
4-Channel Charge-Pump LED Driver
30
25
20
15
10
5
0
100 90 80 70 60 50 40 30 20
EN/PWM Input Pin Duty Cycle (%)
10
Figure 3: AAT3195-3 Current Control Profile
Applications Information
LED Selection
The AAT3195 is specifically intended for driving white
LEDs. However, the device design will allow the AAT3195
to drive most types of LEDs with forward voltage speci-
fications ranging from 2.0V to 4.7V. LED applications
may include mixed arrangements for display backlight-
ing, infrared (IR) diodes, and any other load needing a
constant current source generated from a varying input
voltage. Since the D1 to D4 constant current sinks are
matched with negligible voltage dependence, the con-
stant current channels will be matched regardless of the
specific LED forward voltage (VF) levels.
The low dropout current sinks in the AAT3195 maximize
performance and make it capable of driving LEDs with
high forward voltages. Multiple channels can be com-
bined to obtain a higher LED drive current without
complication. Current sink inputs that are not used
should be disabled. To disable and properly terminate
unused current sink inputs, they must be tied to OUT.
If left unconnected or terminated to ground, the part
will be forced to operate in 2x charge pump mode.
Device Switching Noise Performance
The AAT3195 operates at a fixed frequency of approxi-
mately 1MHz to control noise and limit harmonics that
can interfere with the RF operation of cellular telephone
handsets or other communication devices. Back-injected
noise appearing on the input pin of the charge pump is
20mV peak-to peak, typically ten times less than induc-
tor-based DC/DC boost converter white LED backlight
solutions. The AAT3195 soft-start feature prevents noise
transient effects associated with inrush currents during
start-up of the charge pump circuit.
Shutdown
Since the sink switches are the only power returns for all
loads, there is no leakage current when all of the sink
switches are disabled. To activate the shutdown mode,
hold the EN/SET input low for longer than tOFF (500μs).
In this state, the AAT3195 typically draws less than 1μA
from the input. Data and address registers are reset to
0 in shutdown.
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the following
sections accounts only for efficiency of the charge pump
section itself.
Since the AAT3195 outputs are pure constant current
sinks and typically drive individual loads, it is difficult to
measure the output voltage for a given output to derive
an overall output power measurement. For any given
application, white LED forward voltage levels can differ,
yet the output drive current will be maintained as a
constant.
This makes quantifying output power a difficult task
when taken in the context of comparing to other white
LED driver circuit topologies. A better way to quantify
total device efficiency is to observe the total input power
3195.2008.09.1.0
www.analogictech.com
11
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AAT3195.PDF ] | |
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