AAT AAT3195IJQ-1 4-channel charge-pump led driver Datasheet

PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
General Description
Features
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.
•
•
•
•
•
•
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
WLEDs
OUT
IN
CIN
1µF
CP
1µF
COUT
1µF
C+
AAT3195
C-
D1
D2
EN/SET
S2Cwire
Interface
3195.2008.09.1.0
EN/SET
GND
D3
D4
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1
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Pin Descriptions
Pin #
Symbol
1
D2
2
D1
3
OUT
4
C+
5
IN
EN/SET
(AAT3195-1/-2)
6
EN/PWM
(AAT3195-3)
7
8
CAGND
9
D4
10
D3
Description
LED2 Current Sink Input. D2 is the input of LED2 current sink. Connect LED2’s anode to OUT and its
cathode to D2.
LED1 Current Sink Input. D1 is the input of LED1 current sink. Connect LED1’s anode to OUT and its
cathode to D1.
Charge Pump Output. OUT is the output of the charge pump. Bypass OUT to AGND with a 1μF or
larger ceramic capacitor.
Charge Pump Capacitor Positive Node. Connect a 1μF ceramic capacitor between C+ and C-.
Power source input. Connect IN to the power source, typically the battery. Bypass IN to AGND with
a 1μF or larger ceramic capacitor.
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.
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.
Charge Pump Capacitor Negative Node.
Analog Ground. Connect this pin to the system’s analog ground plane.
LED4 Current Sink Input. D4 is the input of LED4 current sink. Connect LED4’s anode to OUT and its
cathode to D4.
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)
D2
D1
OUT
C+
IN
2
1
10
2
9
3
8
4
7
5
6
D3
D4
AGND
CEN/SET (EN/PWM)
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3195.2008.09.1.0
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Part Number Descriptions
Part Number
Interface
Current Control, Inverting
Full Scale Current
AAT3195IJQ-1
AAT3195IJQ-2
AAT3195IJQ-3
S2Cwire
S2Cwire
PWM
32-step
32-step
Linear
30mA
20mA
30mA
Absolute Maximum Ratings1
Symbol
VIN, VC+, VC-, VOUT,
VDx
VEN/SET, VEN/PWM
TJ
TLEAD
Description
IN, C+, C-, OUT, D1, D2, D3, and D4 Pin Voltages to AGND
EN/SET or EN/PWM Pin Voltage to AGND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
-0.3 to 6.0
V
-0.3 to VIN + 0.3
-40 to 150
300
V
°C
°C
Value
Units
0.625
160
mW
°C/W
Thermal Information2
Symbol
PD
ΘJA
Description
Maximum Power Dissipation
Maximum Thermal Resistance
3
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.
3195.2008.09.1.0
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3
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Electrical Characteristics
IN = EN = 3.6V; CIN = 1μF; COUT = 1μF; CCP = 1μF; TA = -40°C to 85°C unless otherwise noted. Typical values are at
TA = 25°C.
Symbol
Description
Conditions
AAT3195-1/-2/-3 Input Power Supply
Input Voltage Range
IN
IIN
Input Operating Current
IIN(SHDN)
Input Shutdown Current
Charge Pump Section
IOUT
Maximum Output Current
fOSC
Charge Pump Oscillator Frequency
Charge Pump Mode Hysteresis
(AAT3195-1 only)
VIN_(TH)
Charge Pump Mode Hysteresis
(AAT3195-2 only)
tOUT
Output Start-Up Time
AAT3195-1/-2/-3: LED Current Sink Outputs
D1 – D4 Current Accuracy
(AAT3195-1 only)
ID_(MAX)
D1 – D4 Current Accuracy
(AAT3195-2 only)
ΔID_(MAX)
ID_(DATA30)
ID_(10%)
VD_(TH)
4
D1 – D4 Current Matching
D1 – D4 Current Accuracy
(AAT3195-1 only)
D1 – D4 Current Accuracy
(AAT3195-2 only)
D1 – D4 Current Accuracy
(AAT3195-3 only)
D1- D4 Charge Pump Mode Transition
Threshold (AAT3195-1 only)
D1- D4 Charge Pump Mode Transition
Threshold (AAT3195-3 only)
Min
Typ
2.7
EN/SET or EN/PWM = IN; VD1 = VD2 = VD3
= VD4 = IN, excluding ID1-ID4
EN/SET or EN/PWM = IN; ID1 = ID2 = ID3 =
ID4 = FS, excluding ID1-ID4; VIN – VF = 1.5V
Operating, ID1 = ID2 = ID3 = ID4 = FS; D1,
D2, D3 and D4 = OPEN
IN = 5.5V; EN/SET or EN/PWM = GND
0.65
150
0.9
Max
Units
5.5
V
0.6
mA
3.5
mA
7
mA
1
μA
1.15
mA
MHz
ID1 = ID2 = ID3 = ID4 = 30mA
225
mV
ID1 = ID2 = ID3 = ID4 = 20mA
150
mV
EN/SET or EN/PWM ≥ VENH
150
μs
DATA = 1; VIN - VF = 1.5V
27
30
33
mA
DATA = 1; VIN - VF = 1.5V
18
20
22
mA
DATA = 1; VIN - VF = 1.5V
±3
%
DATA = 30; VIN - VF = 1.5V
1.615
1.9
2.185
mA
DATA = 30; VIN - VF = 1.5V
1.144
1.3
1.456
mA
DC = 10%; fPWM = 10kHz; VIN - VF = 1.5V
2.4
mA
ID1 = ID2 = ID3 = ID4 = 30mA
250
mV
ID1 = ID2 = ID3 = ID4 = 20mA
170
mV
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3195.2008.09.1.0
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
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
Conditions
AAT3195-1/-2: EN/SET and S2Cwire Control
EN Input High Threshold Voltage
VEN(H)
VEN(L)
EN Input Low Threshold Voltage
IEN(LKG)
EN Input Leakage Current
tEN/SET(OFF)
EN/SET Input OFF Timeout
tEN/SET(LAT)
EN/SET Input Latch Timeout
EN/SET Input LOW Time
tEN/SET(LOW)
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
PWM Control Turn-On Delay
tPWM(ON)
tEN/PWM
EN/PWM Input OFF Timeout
PWM Control Frequency
fPWM
3195.2008.09.1.0
Min
Typ
Max
1.4
EN/SET ≥ VEN(H)
0.4
1
500
500
75
-1
0.3
50
75
1.4
EN/PWM = IN = 5V
0.4
1
-1
2
0.15
Duty Cycle = 80%
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1
50
Units
V
V
μA
μs
μs
μs
ns
μs
V
V
μA
μs
ms
kHz
5
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Typical Characteristics
Quiescent Current vs. Input Voltage
No Load Operating Current vs. Input Voltage
4.5
Quiescent Current (mA)
Quiescent Current (mA)
0.26
0.25
0.24
0.23
0.22
°
0.21
0.20
85°C
25°C
-40°C
0.19
0.18
2.7
4.0
3.5
3.0
85°C
25°C
-40°C
2.5
2.0
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
Input Voltage (V)
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
AAT3195-2 Efficiency vs. Input Voltage
Current Matching vs. Temperature
(ILED = 20mA; VF = 3.6V)
22.0
100%
80%
70%
60%
50%
40%
21.0
20.5
20.0
19.5
30%
20%
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
19.0
-40
-15
10
35
60
Input Voltage (V)
Temperature (°C)
Turn On to 1X Mode
Turn On to 2X Mode
(VIN = 4.2V; 20.5mA/ch)
(VIN = 3.6V; 20.5mA/ch)
EN/SET
(2V/div)
EN/SET
(2V/div)
VOUT
(2V/div)
VOUT
(2V/div)
VSINK
(2V/div)
VSINK
(2V/div)
IIN
(200mA/div)
IIN
(200mA/div)
Time (200µs/div)
6
D1
D2
D3
D4
21.5
Current (mA)
Efficiency (%)
90%
85
Time (200µs/div)
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3195.2008.09.1.0
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Typical Characteristics
Shutdown Current vs. Temperature
Turn Off from 2X Mode
(20.5mA/ch)
Shutdown Current (µA)
0.14
EN/SET
(2V/div)
VOUT
(1V/div)
IIN
(200mA/div)
5.5V
2.7V
0.12
0.10
0.08
0.06
0.04
0.02
0.00
-40
-15
10
1.2
1.2
1.0
1.0
0.8
0.6
85°C
25°C
-40°C
0.4
3.5
3.9
4.3
4.7
85
EN Input High Threshold Voltage
vs. Input Voltage
VEN(H) (V)
VEN(L) (V)
EN Input Low Threshold Voltage
vs. Input Voltage
3.1
60
Temperature (°C)
Time (200µs/div)
0.2
2.7
35
5.1
0.8
0.6
85°C
25°C
-40°C
0.4
0.2
2.7
5.5
3.1
3.5
Input Voltage (V)
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
EN/SET Input OFF Timeout
vs. Input Voltage
EN/SET Input Latch Timeout
vs. Input Voltage
450
350
400
300
250
200
85°C
25°C
-40°C
150
100
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
TEN/SET(LAT) (µs)
TEN/SET(OFF) (µs)
300
350
250
200
100
2.7
Input Voltage (V)
3195.2008.09.1.0
85°C
25°C
-40°C
150
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
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PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Typical Characteristics
Transition of LED Current
Transition of LED Current
(1.3mA to 20.5mA)
(20.5mA to 1.3mA)
EN
(2V/div)
EN/SET
(2V/div)
4.2V
VOUT
(1V/div)
4.0V
VSINK
(1V/div)
VSINK
(1V/div)
0.5V
IIN
(50mA/div)
IIN
(50mA/div)
VOUT
(1V/div)
1.5V
Time (100µs/div)
Time (100µs/div)
Output Ripple Waveform
VIN
(AC Coupled)
(50mV/div)
(VIN = 3.6V; 2X Mode; 20.5mA Load)
VOUT
(AC Coupled)
(50mV/div)
VSINK
(AC Coupled)
(50mV/div)
Time (500ns/div)
8
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3195.2008.09.1.0
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Functional Block Diagram
C+
IN
C–
OUT
Two-Mode
CP Control
D1
D2
VF Monitoring
4
D3
D4
AGND
IREF
EN/SET
(EN/PWM)
S2Cwire Control
(PWM Control)
DAC
RSET
Functional Description
S2Cwire Interface (AAT3195-1/-2 Only)
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 individually controlled through integrated current sinks powered 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 automatically switches back to 1x mode when there is sufficient
input voltage.
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 system 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 reliability. 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 (500μs).
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 (500μs), the AAT3195-1/-2 enters shutdown mode and draws less than 1μA from the input and
the internal data register is reset to zero.
The AAT3195 requires only three external components:
one 1μF ceramic capacitor for the charge pump flying
capacitor (CP), one 1μF ceramic capacitor at the IN pin
(CIN), and one 1μF ceramic capacitor at the OUT pin
(COUT). The four constant-current outputs of the AAT31951 (D1 to D4) can drive four individual LEDs with a maximum 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.
3195.2008.09.1.0
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 maximum current. Successive rising edges decrease the
LED current as shown in Table 1 and Figure 2 for the
AAT3195-1/-2.
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PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
THI
TLO
TOFF
TLAT
EN/SET
1
2
n-1
Data Reg
n ≤ 32
0
n-1
0
Data
EN Rising
Edges
AAT3195-1
D1-D4 Current
(mA)
AAT3195-2
D1-D4 Current
(mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
30.0
29.0
28.1
27.1
26.1
25.1
24.2
23.2
22.3
21.3
20.3
19.4
18.4
17.4
16.5
15.5
14.5
13.6
12.6
11.6
10.7
9.7
8.7
7.7
6.8
5.8
4.8
3.9
2.9
1.9
1.0
0.5
20.5
19.8
19.2
18.5
17.8
17.2
16.5
15.8
15.2
14.5
13.9
13.2
12.5
11.9
11.2
10.6
9.9
9.2
8.6
7.9
7.3
6.6
5.9
5.3
4.6
4.0
3.3
2.6
2.0
1.3
0.7
0.3
Dx Output LED Current (mA)
Figure 1: S2Cwire Serial Interface Timing.
35
AAT3195-1
AAT3195-2
30
25
20
15
10
5
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
S2Cwire Serial Interface Data Code
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 brightness 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 AAT31953. By changing the duty cycle of the PWM signal from
100% (logic high) to 10%, LEDs sink current can be programmed 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.
Table 1: AAT3195-1/-2 LED Current Setting.
10
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3195.2008.09.1.0
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
D1-D3 Current (mA)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
30
27
24
21
18
15
12
9
6
3
30
Dx Output Current (mA)
EN/PWM Duty Cycle
25
20
15
10
5
0
100
90
80
70
60
50
40
30
20
10
EN/PWM Input Pin Duty Cycle (%)
Table 2: AAT3195-3 LED Current Settings
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 specifications ranging from 2.0V to 4.7V. LED applications
may include mixed arrangements for display backlighting, 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 constant 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 combined 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 approximately 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
3195.2008.09.1.0
20mV peak-to peak, typically ten times less than inductor-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
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11
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
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 voltage 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 voltages 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 efficiency 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 chargepump mode can be expressed as:
η=
POUT VOUT · IOUT VOUT
=
≅
PIN
VIN · IOUT
VIN
-or-
VOUT
η (%) = 100 · V
IN
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 voltage 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.
12
η=
POUT VOUT · IOUT VOUT
=
=
PIN
VIN · 2IOUT 2VIN
-or-
VOUT
η (%) = 100 · 2V
IN
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 consumption, 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 100mΩ. A value of
1μF 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
2x Charge Pump Mode Efficiency
η=
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:
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 counterparts. A ceramic capacitor typically has very low ESR, is
lowest cost, has a smaller PCB footprint, and is nonpolarized. Low ESR ceramic capacitors help maximizes
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
POUT
PIN
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PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
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 typically measured in milliohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1μF are typically made
from NPO or C0G materials. NPO and C0G materials
generally have tight tolerance and are very stable over
3195.2008.09.1.0
temperature. Larger capacitor values are usually composed of X7R, X5R, Z5U, or Y5V dielectric materials.
Large ceramic capacitors (i.e., larger than 2.2μF) are
often available in low cost Y5V and Z5U dielectrics, but
capacitors larger than 1μF 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.
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13
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Evaluation Board Schematic
JP6
DC-
DC+
C3
1µF
J1
1
2
3
VIN
JP5
D1
D2
D3
D4
JP1
JP2
JP3
JP4
GND
1
2
3
4
5
C2
1µF
10
D2
D3
D1
D4
OUT AGND
C+
CIN
EN/SET
9
8
7
6
C1
1µF
U1 AAT3195
GND
GND
J2
R6
100 K
VIN
GND
R3
1K
Cycle
SW3
Up
SW2
Down
SW1
R2
1K
R1
1K
U2
1
2
3
4
VDD
GP5
GP4
GP3
VSS
GP0
GP1
GP2
PIC12F675
VR4
POT10K
8
7
6
C4
1µF
R5
1.5k
LED2
RED
5
R4
1.5k
GND
GND
LED1
GRN
GND
GND
Evaluation Board Layout
Figure 4: AAT3195 Evaluation Board
Top Side Layout.
14
Figure 5: AAT3195 Evaluation Board
Bottom Side Layout.
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3195.2008.09.1.0
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Ordering Information
Package
Interface
Current Level,
Inverting
SC70JW-10
SC70JW-10
SC70JW-10
S Cwire
S2Cwire
PWM
30mA, 32-step
20mA, 32-step
Linear
2
Marking1
Part Number (Tape and Reel)2
3XXYY
AAT3195IJQ-1-T1
AAT3195IJQ-2-T1
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
2.20 ± 0.20
1.75 ± 0.10
0.40 BSC
0.225 ± 0.075
Top View
0.100
7° ± 3°
0.45 ± 0.10
4° ± 4°
0.05 ± 0.05
0.15 ± 0.05
1.10 MAX
0.85 ± 0.15
2.00 ± 0.20
2.10 ± 0.30
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.
3195.2008.09.1.0
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15
PRODUCT DATASHEET
AAT3195
ChargePump
4-Channel Charge-Pump LED Driver
TM
Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual
property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to
support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other
brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
16
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