AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 1
www.analogictech.com
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
the LED forward voltage. The AAT3195 incorporates an
internal RSET and is available in a thermally enhanced,
Pb-free 2x2.1mm 10-lead SC70JW-10 package.
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
IN
C+
C-
EN/SET
OUT
D1
D2
EN/SET
S2Cwire
Interface
CIN
1µF
CP
1µF
COUT
1µF
GND
WLEDs
D3
D4
AAT3195
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
2 3195.2009.06.1.3
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
2 3195.2009.06.1.3
www.analogictech.com
Pin Descriptions
Pin # Symbol Description
1D2
LED2 Current Sink Input. D2 is the input of LED2 current sink. Connect LED2’s anode to OUT and its
cathode to D2.
2D1
LED1 Current Sink Input. D1 is the input of LED1 current sink. Connect LED1’s anode to OUT and its
cathode to D1.
3 OUT Charge Pump Output. OUT is the output of the charge pump. Bypass OUT to AGND with a 1F or
larger ceramic capacitor.
4 C+ Charge Pump Capacitor Positive Node. Connect a 1F ceramic capacitor between C+ and C-.
5IN
Power source input. Connect IN to the power source, typically the battery. Bypass IN to AGND with
a 1F or larger ceramic capacitor.
6
EN/SET
(AAT3195-1/-2)
LED Enable and serial control input. EN/SET is the ON/OFF control for the LED and the S2Cwire
digital input for the AAT3195-1/-2 to control serially the LED brightness according to the maximum
current set by RSET
.
EN/PWM
(AAT3195-3)
LED ON/OFF and PWM control input. This logic input controls the LED outputs for the AAT3195-3.
Alternatively, a PWM signal from a GPIO or an equivalent signal from a separate controller can be
used to control LED output current linearly. A PWM signal, ranging from 10% to 100% duty cycle,
controls the LED current linearly between ZS and FS.
7 C- Charge Pump Capacitor Negative Node.
8 AGND Analog Ground. Connect this pin to the system’s analog ground plane.
9D4
LED4 Current Sink Input. D4 is the input of LED4 current sink. Connect LED4’s anode to OUT and its
cathode to D4.
10 D3 LED3 Current Sink Input. D3 is the input of LED3 current sink. Connect LED3’s anode to OUT and its
cathode to D3.
Pin Configuration
SC70JW-10
(Top View)
1
2
3
4
5
10
9
8
7
6
D2
D1
OUT
C+
IN
D3
D4
AGND
C-
EN/SET (EN/PWM)
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 3
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 3
www.analogictech.com
Part Number Descriptions
Part Number Interface Current Control, Inverting Full Scale Current
AAT3195IJQ-1 S2Cwire 32-step 30mA
AAT3195IJQ-2 S2Cwire 32-step 20mA
AAT3195IJQ-3 PWM Linear 30mA
Absolute Maximum Ratings1
Symbol Description Value Units
VIN, VC+, VC-, VOUT
,
VDx
IN, C+, C-, OUT, D1, D2, D3, and D4 Pin Voltages to AGND -0.3 to 6.0 V
VEN/SET
, VEN/PWM EN/SET or EN/PWM Pin Voltage to AGND -0.3 to VIN + 0.3 V
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C
Thermal Information2
Symbol Description Value Units
PDMaximum Power Dissipation3625 mW
ΘJA Maximum Thermal Resistance 160 °C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 circuit board.
3. Derate 6.25mW/°C above 40°C ambient temperature.
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
4 3195.2009.06.1.3
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AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
4 3195.2009.06.1.3
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Electrical Characteristics
IN = EN = 3.6V; CIN = 1F; COUT = 1F; CCP = 1F; TA = -40°C to 85°C unless otherwise noted. Typical values are at
TA = 25°C.
Symbol Description Conditions Min Typ Max Units
AAT3195-1/-2/-3 Input Power Supply
IN Input Voltage Range 2.7 5.5 V
IIN Input Operating Current
EN/SET or EN/PWM = IN; VD1 = VD2 = VD3
= VD4 = IN, excluding ID1-ID4 0.6 mA
EN/SET or EN/PWM = IN; ID1 = ID2 = ID3 =
ID4 = FS, excluding ID1-ID4; VIN – VF = 1.5V 3.5 mA
Operating, ID1 = ID2 = ID3 = ID4 = FS; D1,
D2, D3 and D4 = OPEN 7mA
IIN(SHDN) Input Shutdown Current IN = 5.5V; EN/SET or EN/PWM = GND 1 A
Charge Pump Section
IOUT Maximum Output Current 150 mA
fOSC Charge Pump Oscillator Frequency 0.65 0.9 1.15 MHz
VIN_(TH)
Charge Pump Mode Hysteresis
(AAT3195-1 only) ID1 = ID2 = ID3 = ID4 = 30mA 225 mV
Charge Pump Mode Hysteresis
(AAT3195-2 only) ID1 = ID2 = ID3 = ID4 = 20mA 150 mV
tOUT Output Start-Up Time EN/SET or EN/PWM VENH 150 s
AAT3195-1/-2/-3: LED Current Sink Outputs
ID_(MAX)
D1 – D4 Current Accuracy
(AAT3195-1 only) DATA = 1; VIN - VF = 1.5V 27 30 33 mA
D1 – D4 Current Accuracy
(AAT3195-2 only) DATA = 1; VIN - VF = 1.5V 18 20 22 mA
ID_(MAX) D1 – D4 Current Matching DATA = 1; VIN - VF = 1.5V ±3 %
ID_(DATA30)
D1 – D4 Current Accuracy
(AAT3195-1 only) DATA = 30; VIN - VF = 1.5V 1.672 1.9 2.128 mA
D1 – D4 Current Accuracy
(AAT3195-2 only) DATA = 30; VIN - VF = 1.5V 1.144 1.3 1.456 mA
ID_(10%) D1 – D4 Current Accuracy
(AAT3195-3 only) DC = 10%; fPWM = 10kHz; VIN - VF = 1.5V 2.4 mA
VD_(TH)
D1- D4 Charge Pump Mode Transition
Threshold (AAT3195-1 only) ID1 = ID2 = ID3 = ID4 = 30mA 250 mV
D1- D4 Charge Pump Mode Transition
Threshold (AAT3195-3 only) ID1 = ID2 = ID3 = ID4 = 20mA 170 mV
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 5
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 5
www.analogictech.com
Electrical Characteristics
IN = EN = 3.6V; CIN = 1 F; COUT = 1F; CCP = 1F; TA=-40°C to 85°C unless otherwise noted. Typical values are at TA
= 25°C.
Symbol Description Conditions Min Typ Max Units
AAT3195-1/-2: EN/SET and S2Cwire Control
VEN(H) EN Input High Threshold Voltage 1.4 V
VEN(L) EN Input Low Threshold Voltage 0.4 V
IEN(LKG) EN Input Leakage Current EN/SET VEN(H) -1 1 A
tEN/SET(OFF) EN/SET Input OFF Timeout 500 s
tEN/SET(LAT) EN/SET Input Latch Timeout 500 s
tEN/SET(LOW) EN/SET Input LOW Time 0.3 75 s
tENSET(H-MIN) EN/SET Minimum High Time 50 ns
tENSET(H-MAX) EN/SET Maximum High Time 75 s
AAT3195-3: EN/PWM Current Control
VEN(H) EN/PWM Input High Threshold Voltage 1.4 V
VEN(L) EN/PWM Input Low Threshold Voltage 0.4 V
IEN(LKG) EN/PWM Input Leakage Current EN/PWM = IN = 5V -1 1 A
tPWM(ON) PWM Control Turn-On Delay 2 s
tEN/PWM EN/PWM Input OFF Timeout 0.15 1 ms
fPWM PWM Control Frequency Duty Cycle = 80% 50 kHz
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
6 3195.2009.06.1.3
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
6 3195.2009.06.1.3
www.analogictech.com
Typical Characteristics
Quiescent Current vs. Input Voltage
Input Voltage (V)
Quiescent Current (mA)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
0.18
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
°
85°C
25°C
-40°C
No Load Operating Current vs. Input Voltage
Input Voltage (V)
Quiescent Current (mA)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
2.0
2.5
3.0
3.5
4.0
4.5
85°C
25°C
-40°C
AAT3195-1 Efficiency vs. Input Voltage
(ILED = 30mA; VF = 4V)
Input Voltage (V)
Efficiency (%)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
0%
20%
40%
60%
80%
100%
AAT3195-1 Current Matching vs. Temperature
(VIN = 3.6V)
Temperature (°C)
Current (mA)
-40 -15 10 35 60 85
24
26
28
30
32
34
36
D1
D2
D3
D4
AAT3195-2 Efficiency vs. Input Voltage
(ILED = 20mA; VF = 3.6V)
Input Voltage (V)
Efficiency (%)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
20%
30%
40%
50%
60%
70%
80%
90%
100%
AAT3195-2 Current Matching vs. Temperature
Temperature (°C)
Current (mA)
-40 -15 10 35 60 85
19.0
19.5
20.0
20.5
21.0
21.5
22.0
D1
D2
D3
D4
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 7
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AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 7
www.analogictech.com
Typical Characteristics
Turn On to 1X Mode
(VIN = 4.2V; 20.5mA/ch)
Time (200µs/div)
VOUT
(2V/div)
VSINK
(2V/div)
EN/SET
(2V/div)
IIN
(200mA/div)
Turn On to 2X Mode
(VIN = 3.6V; 20.5mA/ch)
Time (200µs/div)
VOUT
(2V/div)
VSINK
(2V/div)
EN/SET
(2V/div)
IIN
(200mA/div)
Turn Off from 2X Mode
(20.5mA/ch)
Time (200µs/div)
VOUT
(1V/div)
EN/SET
(2V/div)
IIN
(200mA/div)
Shutdown Current vs. Temperature
Temperature (°C)
Shutdown Current (µA)
-40 -15 10 35 60 85
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
5.5V
2.7V
EN Input Low Threshold Voltage
vs. Input Voltage
Input Voltage (V)
VEN(L) (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
0.2
0.4
0.6
0.8
1.0
1.2
85°C
25°C
-40°C
EN Input High Threshold Voltage
vs. Input Voltage
Input Voltage (V)
VEN(H) (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
0.2
0.4
0.6
0.8
1.0
1.2
85°C
25°C
-40°C
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
8 3195.2009.06.1.3
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
8 3195.2009.06.1.3
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Typical Characteristics
EN/SET Input OFF Timeout
vs. Input Voltage
Input Voltage (V)
TEN/SET(OFF) (µs)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
100
150
200
250
300
350
400
450
85°C
25°C
-40°C
EN/SET Input Latch Timeout
vs. Input Voltage
Input Voltage (V)
TEN/SET(LAT) (µs)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
100
150
200
250
300
350
85°C
25°C
-40°C
Transition of LED Current
(1.3mA to 20.5mA)
Time (100µs/div)
VOUT
(1V/div)
VSINK
(1V/div)
EN
(2V/div)
IIN
(50mA/div)
4.2V
1.5V
Transition of LED Current
(20.5mA to 1.3mA)
Time (100µs/div)
VOUT
(1V/div)
VSINK
(1V/div)
EN/SET
(2V/div)
IIN
(50mA/div)
4.0V
0.5V
AAT3195-1 Output Ripple Waveform
(VIN = 3.6V; 2X Mode; 30mA Load)
Time (500ns/div)
VOUT
(AC Coupled)
(100mV/div)
VIN
(AC Coupled)
(100mV/div)
VSINK
(AC Coupled)
(100mV/div)
AAT3195-2 Output Ripple Waveform
(VIN = 3.6V; 2X Mode; 20.5mA Load)
Time (500ns/div)
VOUT
(AC Coupled)
(50mV/div)
VIN
(AC Coupled)
(50mV/div)
VSINK
(AC Coupled)
(50mV/div)
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 9
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 9
www.analogictech.com
Functional Description
The AAT3195 charge-pump solution is designed to drive
up to four white LEDs. The charge pump operates from
a 2.7V to 5.5V power source and converts it to voltage
levels necessary to drive the LEDs. LED current is indi-
vidually controlled through integrated current sinks pow-
ered from the output of the charge pump. Low 1x
charge-pump output resistance and low-drop voltage
current sinks allow the charge pump to stay in 1x mode
with an input voltage as low as 3.75V and LED forward
voltages as high as 3.5V. Once in 2x mode, the charge
pump monitors the input supply voltage and automati-
cally switches back to 1x mode when there is sufficient
input voltage.
The AAT3195 requires only three external components:
one 1F ceramic capacitor for the charge pump flying
capacitor (CP), one 1F ceramic capacitor at the IN pin
(CIN), and one 1F ceramic capacitor at the OUT pin
(COUT). The four constant-current outputs of the AAT3195-
1 (D1 to D4) can drive four individual LEDs with a max-
imum current of 30mA each or, in the case of the
AAT3195-2, with a maximum current up to 20mA.
AnalogicTech’s single-wire S2Cwire serial interface
enables the AAT3195-1/-2 and changes the current sink
current in 32 steps through the EN/SET pin. The
AAT3195-3 uses an external PWM signal to enable the IC
and control the brightness of the LEDs.
S2Cwire Interface (AAT3195-1/-2 Only)
The LED output current of the AAT3195-1/-2 is controlled
by AnalogicTech’s S2Cwire serial interface. Since the LED
current is programmable, no PWM or additional control
circuitry is needed to control LED brightness. This feature
greatly reduces the burden on a microcontroller or sys-
tem IC to manage LED or display brightness, allowing
the user to “set it and forget it.” With its high-speed
serial interface (1MHz data rate), the LED current can be
changed quickly and easily. Also the non-pulsating LED
current reduces system noise and improves LED reliabil-
ity. The S2Cwire interface relies on the number of rising
edges to the EN/SET pin to set the register. A typical
write protocol is a burst of EN/SET rising edges, followed
by a pause with EN/SET held high for at least tLAT (500s).
The programmed current is then seen at the current sink
outputs. When EN/SET is held low for an amount of time
longer than tOFF (500s), the AAT3195-1/-2 enters shut-
down mode and draws less than 1A from the input and
the internal data register is reset to zero.
The AAT3195-1/-2’s serial interface reduces the LED
current on each rising pulse of the enable input. If the
AAT3195-1/-2 is in shutdown, the first rising edge of
the EN/SET input turns on the LED driver to the maxi-
mum current. Successive rising edges decrease the
LED current as shown in Table 1 and Figure 2 for the
AAT3195-1/-2.
Functional Block Diagram
C–C+ OUT
AGND
IN
D3
D2
D1
S2Cwire Control
(PWM Control) DAC
EN/SET
(EN/ PWM)
Two-Mode
CP Control
VF Monitoring 4
IREF
D4
RSET
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
10 3195.2009.06.1.3
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1
EN/SET
2n-1 n ≤ 32
Data Reg 0 n-1 0
THI
TLO TLAT TOFF
Figure 1: S2Cwire Serial Interface Timing.
Data EN Rising
Edges
AAT3195-1
D1-D4 Current
(mA)
AAT3195-2
D1-D4 Current
(mA)
1 1 30.0 20.5
2 2 29.0 19.8
3 3 28.1 19.2
4 4 27.1 18.5
5 5 26.1 17.8
6 6 25.1 17.2
7 7 24.2 16.5
8 8 23.2 15.8
9 9 22.3 15.2
10 10 21.3 14.5
11 11 20.3 13.9
12 12 19.4 13.2
13 13 18.4 12.5
14 14 17.4 11.9
15 15 16.5 11.2
16 16 15.5 10.6
17 17 14.5 9.9
18 18 13.6 9.2
19 19 12.6 8.6
20 20 11.6 7.9
21 21 10.7 7.3
22 22 9.7 6.6
23 23 8.7 5.9
24 24 7.7 5.3
25 25 6.8 4.6
26 26 5.8 4.0
27 27 4.8 3.3
28 28 3.9 2.6
29 29 2.9 2.0
30 30 1.9 1.3
31 31 1.0 0.7
32 32 0.5 0.3
Table 1: AAT3195-1/-2 LED Current Setting.
S2Cwire Serial Interface Data Code
Dx Output LED Current (mA)
1 3 5 7 9 111315171921232527 29 31
0
5
10
15
20
25
30
35
AAT3195-1
AAT3195-2
Figure 2: AAT3195-1/-2 Current Control Profile
PWM Control (AAT3195-3 only)
PWM (Pulse Width Modulation) is an industry-standard
technique of controlling LED brightness by modulating
the conduction duty cycle of the LED current. LED bright-
ness is determined by the average value of the PWM
signal multiplied by the LED’s intensity where intensity is
proportional to the LED drive current. A PWM control
signal can be applied to the EN/PWM pin of the AAT3195-
3. By changing the duty cycle of the PWM signal from
100% (logic high) to 10%, LEDs sink current can be pro-
grammed from 30mA to 3.0mA. To save power when not
used or not needed, the AAT3195-3 can be shut down by
holding the EN/PWM pin low for >1ms.
Lastly, Table 2 and Figure 3 illustrate the AAT3195-3's
LED current control profile as a function of a PWM control
signal.
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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EN/PWM Duty Cycle D1-D3 Current (mA)
100% 30
90% 27
80% 24
70% 21
60% 18
50% 15
40% 12
30% 9
20% 6
10% 3
Table 2: AAT3195-3 LED Current Settings EN/PWM Input Pin Duty Cycle (%)
Dx Output Current (mA)
0
5
10
15
20
25
30
10
20
3040
50
60
7080
90100
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 (500s).
In this state, the AAT3195 typically draws less than 1A
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
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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to the device for a given LED current drive level. The
best white LED driver for a given application should be
based on trade-offs of size, external component count,
reliability, operating range, and total energy usage...not
just % efficiency.
The AAT3195 efficiency may be quantified under very
specific conditions and is dependent upon the input volt-
age versus the output voltage seen across the loads
applied to outputs D1 through D4 for a given constant
current setting. Depending on the combination of VIN and
voltages sensed at the current sinks, the device will
operate in load switch mode. When any one of the volt-
ages sensed at the current sinks nears dropout, the
device will operate in 2x charge pump mode. Each of
these modes will yield different efficiency values. Refer
to the following two sections for explanations for each
operational mode.
1x Mode Efficiency
The AAT3195 1x mode is operational at all times and
functions alone to enhance device power conversion effi-
ciency when VIN is higher than the voltage across the
load. When in 1x mode, voltage conversion efficiency is
defined as output power divided by input power:
An expression for the ideal efficiency (η) in 1X charge-
pump mode can be expressed as:
η = POUT
=
VOUT · IOUT ≅ VOUT
PIN VIN · IOUT VIN
-or-
η (%) = 100 · VOUT
VIN
2x Charge Pump Mode Efficiency
The AAT3195 contains a fractional charge pump which
will boost the input supply voltage in the event where VIN
is less than the voltage required to supply the output.
The efficiency (η) can be simply defined as a linear volt-
age regulator with an effective output voltage that is
equal to one and one half or two times the input voltage.
Efficiency (η) for an ideal 2x charge pump can typically
be expressed as the output power divided by the input
power.
η = POUT
PIN
In addition, with an ideal 2x charge pump, the output
current may be expressed as 1/3 of the input current.
The expression to define the ideal efficiency (η) can be
rewritten as:
η = POUT
=
VOUT · IOUT
=
VOUT
PIN VIN · 2IOUT 2VIN
-or-
η (%) = 100 · VOUT
2VIN
For a charge pump with an output of 5V and a nominal
input of 3.5V, the theoretical efficiency is 71%. Due to
internal switching losses and IC quiescent current con-
sumption, the actual efficiency can be measured at 51%.
These figures are in close agreement for output load
conditions from 1mA to 100mA. Efficiency will decrease
substantially as load current drops below 1mA or when
the voltage level at VIN approaches the voltage level at
VOUT
.
Capacitor Selection
Careful selection of the three external capacitors CIN, CP
,
and COUT is important because they will affect turn-on
time, output ripple, and transient performance. 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 100m. A value of
1F for all four capacitors is a good starting point when
choosing capacitors. If the constant current sinks are
only programmed for light current levels, then the
capacitor size may be decreased.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended
over all other types of capacitors for use with the
AAT3195. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counter-
parts. A ceramic capacitor typically has very low ESR, is
lowest cost, has a smaller PCB footprint, and is non-
polarized. Low ESR ceramic capacitors help maximizes
charge pump transient response. Since ceramic capaci-
tors are non-polarized, they are not prone to incorrect
connection damage.
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 13
www.analogictech.com
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 connec-
tions, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in mil-
liohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1F are typically made
from NPO or C0G materials. NPO and C0G materials
generally have tight tolerance and are very stable over
temperature. Larger capacitor values are usually com-
posed of X7R, X5R, Z5U, or Y5V dielectric materials.
Large ceramic capacitors (i.e., larger than 2.2F) are
often available in low cost Y5V and Z5U dielectrics, but
capacitors larger than 1F are not typically required for
AAT3195 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.
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
14 3195.2009.06.1.3
www.analogictech.com
Evaluation Board Schematic
VDD
1
GP5
2
GP4
3
GP3
4GP2 5
GP1 6
GP0 7
VSS 8
PIC12F675
U2
C3
1µF
C2
1µF
C1
1µF
C4
1µF
1K
R1
1K
R2
1K
R3
123
J1
RED
LED2
DC+DC-
D2D1D3
GND
VIN
GND
GND
VR4
POT10K
GRN
LED1
R4
1.5k
R5
1.5k
GND
GND
JP1 JP2 JP3
GND
J2
100K
R6
GND
VIN
JP5
GND
JP6
Down SW1
Up SW2
Cycle SW3
D4
JP4
D2
1
D1
2
OUT
3
C+
4C- 7
AGND 8
D4 9
D3 10
EN/SET 6
IN
5
U1 AAT3195
Evaluation Board Layout
Figure 4: AAT3195 Evaluation Board Figure 5: AAT3195 Evaluation Board
Top Side Layout. Bottom Side Layout.
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 15
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3195.2009.06.1.3 15
www.analogictech.com
Ordering Information
Package Interface Current Level,
Inverting Marking1Part Number (Tape and Reel)2
SC70JW-10 S2Cwire 30mA, 32-step 3FXYY AAT3195IJQ-1-T1
SC70JW-10 S2Cwire 20mA, 32-step 3XXYY AAT3195IJQ-2-T1
SC70JW-10 PWM Linear AAT3195IJQ-3-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor
products that are in compliance with current RoHS standards, including the requirement that lead not exceed
0.1% by weight in homogeneous materials. For more information, please visit our website at
http://www.analogictech.com/about/quality.aspx.
Package Information
SC70JW-10
0.45
±
0.10
0.05
±
0.05
2.10
±
0.30
4
°
±
4
°
0.15
±
0.05
2.00
±
0.20
7
°
±
3
°
0.85
±
0.15
1.10 MAX
0.100
0.225
±
0.075
1.75
±
0.10
2.20
±
0.20
0.40 BSC
Top View
Side View End View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
16 3195.2009.06.1.3
www.analogictech.com
AAT3195
4-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
16 3195.2009.06.1.3
www.analogictech.com
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Phone (408) 737-4600
Fax (408) 737-4611
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