Analogic AAT3192IJQ-4-T1 2-channel charge-pump led driver Datasheet

PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
General Description
Features
The AAT3192 is a charge-pump based, current-sink
white LED driver capable of driving one or two 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 AAT3192 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 AAT3192 is available in the 2x2mm, 10-lead SC70JW10 package.
Drives up to 2 LEDs at up to 30mA, each
Automatic Switching Between 1x and 2x Modes
0.9MHz Switching Frequency
Linear LED Output Current Control
▪ Single-wire, S2Cwire Interface
• AAT3192-1: 16-step
• AAT3192-2: 8-step
• AAT3192-3: 4-step
▪ ON/OFF or PWM Interface
• AAT3192-4
±10% LED Output Current Accuracy
±3% LED Output Current Matching
Low-Current Shutdown Mode
Built-in Thermal Protection
Automatic Soft-Start
Available in 2x2mm SC70JW-10 Package
Applications
•
•
•
•
Entry
Entry
Entry
Entry
Level
Level
Level
Level
Cordless Phone Handsets
Digital Cameras
Mobile Phone Handsets
MP3 and PMP Players
Typical Application
Input Voltage
2.7V to 5.5V
IN
OUT
C+
C IN
1μF
CP
1μF
AAT3192-1
C-
EN/SET
S2Cwire
Interface
EN/SET
RSET
C OUT
1μF
WLEDs
OSRAM LW M 678
or equivalent
D1
D2
GND
R SET
14.3kΩ
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1
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Pin Descriptions
Pin
Symbol
1
N/C
2
OUT
3
4
CC+
5
IN
EN/SET
(AAT3192-1/-2/-3)
6
EN/PWM
(AAT3192-4)
7
RSET
8
GND
9
D2
10
D1
Description
No connection.
Charge pump output. OUT is the output of the charge pump. Bypass OUT to GND with a 1μF or
larger ceramic capacitor.
Charge pump capacitor negative node.
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 GND 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 AAT3192-1/-2/-3 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 AAT3192-4.
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.
A 1% tolerance resistor from this pin to GND sets the maximum LED current level. For optimal LED
output current accuracy and matching in the AAT3192-1/-2/-4, a 14.3kΩ resistor sets each full-scale
output current to 20mA, maximum. For the AAT3192-3, a 11.5kΩ resistor is recommended.
Ground. Connect this pin to the system’s ground plane.
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.
Pin Configuration
SC70JW-10
(Top View)
N/C
OUT
CC+
IN
2
1
10
2
9
3
8
4
7
5
6
D1
D2
GND
RSET
EN/SET
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3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Part Number Descriptions
Part Number
Interface
Current Control, Inverting
AAT3192IJQ-1
AAT3192IJQ-2
AAT3192IJQ-3
AAT3192IJQ-4
S2Cwire
S2Cwire
S2Cwire
PWM
16-step
8-step
4-step
Linear
Absolute Maximum Ratings1
Symbol
Description
IN, C+, C-, OUT, D1, D2, and RSET Pin Voltages to GND
EN/SET or EN/PWM Pin Voltage to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
-0.3 to 6.0
-0.3 to VIN + 0.3
-40 to 150
300
V
V
°C
°C
Value
Units
625
160
mW
°C/W
Thermal Information
Symbol
PD
θJA
Description
Maximum Power Dissipation2, 3
Maximum Thermal Resistance2
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.
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PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Electrical Characteristics1
IN = EN = 3.6V; CIN = 1μF; COUT = 1μF; CCP = 1μF; RSET = 14.3kΩ; TA =-40°C to 85°C unless otherwise noted. Typical
values are at TA = 25°C.
Symbol
Description
Conditions
AAT3192-1/2/3/4 Input Power Supply
IN
Input Voltage Range
IIN
Input Operating Current
IIN(SHDN)
Input Shutdown Current
Charge Pump Section
OUT Maximum Output Current
IOUT
fOSC
Charge Pump Oscillator Frequency
VIN_(TH)
Charge Pump Mode Hysteresis
tOUT
Output Start-Up Time
AAT3192-1/-2/-4: LED Current Sink Outputs
ID_(MAX)
D1 - D2 Current Accuracy
ΔID_(MAX)
D1 - D2 Current Matching
D1 - D2 Current Accuracy
ID_(DATA15)
(AAT3192-1 only)
D1 - D2 Current Accuracy
ID_(DATA8)
(AAT3192-2 only)
D1 - D2 Current Accuracy
ID_(10%)
(AAT3192-4 only)
D1 - D2 Charge Pump Mode
VD_(TH)
Transition Threshold
Min
Typ
2.7
EN/SET or EN/PWM = IN; VD1 = VD2 = IN,
excluding ID1-ID2
EN/SET or EN/PWM = IN; ID1 = ID2 = FS,
excluding ID1-ID2; VIN – VF = 1.5V
Operating, ID1 = ID2 = FS; D1 and D2 = OPEN
IN = 5.5V; EN/SET or EN/PWM = GND
Max
Units
5.5
V
2.5
2.5
0.65
ID1 = ID2 = 20mA; Excluding AAT3192-4,
PWM Option
EN/SET or EN/PWM = IN
mA
7.0
1
μA
100
0.9
1.15
mA
MHz
115
250
mV
150
μs
DATA = 1; VIN - VF = 1.5V
DATA = 1; VIN - VF = 1.5V
18
20
±3
22
mA
%
DATA = 15; VIN - VF = 1.5V
1.0
1.3
1.56
mA
DATA = 8; VIN - VF = 1.5V
1.0
1.3
1.56
mA
DC = 10%; fPWM = 10kHz; VIN - VF = 1.5V
2.4
mA
ID1 = ID2 = 20mA
125
mV
1. The AAT3192 is guaranteed to meet performance specification over the -40°C to 85°C operating temperature range and is assured by design, characterization and correlation
with statistical process controls.
4
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3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Electrical Characteristics1
IN = EN = 3.6V; CIN = 1μF; COUT = 1μF; CCP = 1μF; RSET = 14.3kΩ; TA =-40°C to 85°C unless otherwise noted. Typical
values are at TA = 25°C.
Symbol
Description
Conditions
AAT3192-3: LED Current Sink Outputs
ID_(MAX)
D1 - D2 Current Accuracy
ΔID_(MAX)
D1 - D2 Current Matching
ID_(DATA4)
D1 - D2 Current Accuracy
D1 - D2 Charge Pump Mode Transition
VD_(TH)
Threshold
AAT3192-1/-2/-3: EN/SET and S2Cwire Control
EN Input High Threshold Voltage
VENH
VENL
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
tEN/SET(LOW)
EN/SET Input LOW Time
tENSET(H-MIN)
EN/SET Minimum High Time
tENSET(H-MAX)
EN/SET Maximum High Time
AAT3192-4: EN/PWM Current Control
VENH
EN/PWM Input High Threshold Voltage
EN/PWM Input Low Threshold Voltage
VENL
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
RSET = 11.5kΩ; DATA = 1; VIN - VF = 1.5V
RSET = 11.5kΩ; DATA = 1; VIN - VF = 1.5V
RSET = 11.5kΩ; DATA = 4; VIN - VF = 1.5V
Min
Typ
Max
Units
18
20
±3
0.9
22
mA
%
mA
0.72
RSET = 11.5kΩ; ID1 = ID2 = 20mA
1.1
125
mV
1.4
EN/SET = IN = 5V
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%
1
50
V
V
μA
μs
μs
μs
ns
μs
V
V
μA
μs
ms
kHz
1. The AAT3192 is guaranteed to meet performance specification over the -40°C to 85°C operating temperature range and is assured by design, characterization and correlation
with statistical process controls.
3192.2008.07.1.3
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PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Typical Characteristics
Shutdown Current vs. Temperature
Operating Current (No Load)
vs. Input Voltage
0.010
3.50
0.008
IQ (mA)
3.40
IIN(SHDN) (µA)
3.60
85°C
3.30
25°C
3.20
3.10
3.00
2.7
3.1
3.5
3.9
4.3
4.7
5.5V
0.004
0.002
0°C
-45°C
0.006
5.1
2.7V
0.000
-40
5.5
-15
Efficiency vs. Input Voltage
60
85
Current Matching vs. Temperature
21.0
100%
90%
20.5
Current (mA)
80%
Efficiency (%)
35
Temperature (°°C)
VIN (V)
70%
60%
30mA
VF = 3.8V
50%
40%
30%
10mA
VF = 3.2V
20%
10%
0%
2.7
10
3.1
3.5
3.9
20mA
VF = 3.5V
4.3
D1
20.0
19.5
19.0
D2
18.5
4.7
5.1
5.5
18.0
-40
Input Voltage (V)
-15
10
35
60
85
Temperature (°C)
Turn On to 2X Mode
Turn Off from 2X Mode
(VIN = 3.6V; 19.6mA/ch)
(2X Mode; 19.6mA/ch)
EN/SET
(2V/div)
EN/SET
(2V/div)
VF
(2V/div)
VF
(1V/div)
VSINK
(2V/div)
IIN
(200mA/div)
IIN
(200mA/div)
Time (200µs/div)
6
Time (200µs/div)
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3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Typical Characteristics
Turn On to 1X Mode
Maximum LED Current vs RSET
(VIN = 4.2V; 19.6mA/ch)
32
EN/SET
(2V/div)
28
VF
(2V/div)
20
ILED (mA)
24
VSINK
(2V/div)
16
12
8
IIN
(200mA/div)
4
0
8
13
18
1.2
1.2
1.0
1.0
0.8
0.8
85°C
0.4
0.2
2.7
-40°C
0.6
3.5
3.9
-40°C
0.4
0.2
3.1
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
EN/SET Input Latch Timeout vs. Input Voltage
EN/SET Input OFF Timeout vs. Input Voltage
350
350
85°C
85°C
300
TEN/SET(OFF) (µs)
300
TEN/SET(LAT) (µs)
25°C
85°C
Input Voltage (V)
250
25°C
200
-40°C
150
100
2.7
33
EN Input Low Threshold Voltage
vs. Input Voltage
VENL (V)
VENH (V)
EN Input High Threshold Voltage
vs. Input Voltage
25°C
28
RSET (kΩ
Ω)
Time (200µs/div)
0.6
23
3.1
3.5
3.9
4.3
4.7
5.1
5.5
250
-40°C
150
100
2.7
Input Voltage (V)
3192.2008.07.1.3
25°C
200
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
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PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Typical Characteristics
Transition of LED Current
Transition of LED Current
(19.6mA to 1.3mA)
(1.3mA to 19.6mA)
EN
(2V/div)
EN
(2V/div)
VOUT
(1V/div)
VSINK
(1V/div)
VOUT
(1V/div)
4.0V
VSINK
(1V/div)
0.5V
IIN
(50mA/div)
4.2V
1.5V
IIN
(50mA/div)
Time (100µs/div)
Time (100µs/div)
Output Ripple Waveform
Input Current vs. Input Voltage
(2X Mode; 20mA Load)
(Excluding AAT3192-4, PWM Option)
200
VIN
(AC Coupled)
(20mV/div)
Input Current (mA)
180
VOUT
(AC Coupled)
(20mV/div)
VSINK
(AC Coupled)
(50mV/div)
160
VIN Rising
140
120
100
ILED = 20mA
80
60
40
ILED = 10mA
20
0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Input Voltage (V)
Time (1µs/div)
8
VIN Falling
ILED = 30mA
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3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Functional Block Diagram
C+
C-
OUT
Two-Mode
CP Control
IN
D1
VF Monitoring
2
D2
GND
IREF
EN/SET
(EN/PWM)
S2Cwire Control
(PWM Control)
Functional Description
The AAT3192 is a low-cost charge-pump solution designed
to drive up to two 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 AAT3192 requires only four external components:
one 1μF ceramic capacitor for the charge pump flying
capacitors (CP), one 1μF ceramic input capacitor (CIN),
one 1μF ceramic output capacitor (COUT) and a resistor
3192.2008.07.1.3
DAC
RSET
(RSET) to set the maximum LED current. The AAT3192
can drive two constant output sinks (D1 and D2) with up
to 30mA maximum current each. AnalogicTech’s S2Cwire
serial interface enables the AAT3192-1/-2/-3 and changes the current sink magnitudes through the EN/SET pin.
The AAT3192-4 uses an external PWM signal to enable
the IC and control the brightness of the LEDs.
Constant Current Control using RSET
The maximum current is programmed by an external
resistor at the RSET pin. Using a 14.3kΩ external resistor at the RSET pin, the AAT3192-1/-2/-4 includes an
integrated serial LED current control that sets the fullscale LED current between 20mA and 0.63mA. For the
AAT3192-3, a 11.5kΩ external resistor at the RSET pin
sets the full-scale LED current between 20mA and
1.3mA. The full-scale LED current can set higher or lower
than 20mA; see Table 5. For maximum accuracy, a 1%
tolerance resistor is recommended.
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PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
S2Cwire Serial Interface
(AAT3192-1/-2/-3 only)
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 AAT3192 enters into shutdown mode and draws less than 1μA from the input and
the internal data register is reset to zero.
The LED output current of the AAT3192 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
The AAT3192-1/2/3’s serial interface reduces the LED
current on each rising pulse of the enable input. If the
AAT3192 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 AAT3192-1. For the
AAT3192-2, Table 2 and Figure 3 illustrate an 8-step LED
current control profile. For the AAT3192-3, Table 3 and
Figure 4 illustrate a 4-step LED current control profile.
THI
TLO
TOFF
TLAT
EN/SET
1
2
n-1
Data Reg
n ≤ 16
0
n-1
0
Figure 1: S2C Serial Interface Timing.
EN Rising Edges
D1-D2 Current (mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
20
18.7
17.3
16
14.7
13.3
12
10.7
9.3
8
6.7
5.3
4
2.7
1.3
0.63
20.00
Dx Output Current (mA)
Data
15.00
10.00
5.00
0.00
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
S2Cwire Interface Data Code
Figure 2: AAT3192-1 Current Control Profile.
Table 1: AAT3192-1 LED Current Settings.
10
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3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Data
EN Rising Edges
D1-D2 Current (mA)
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
20
17.3
14.7
12
9.3
6.7
4
1.3
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 into the EN/PWM pin of the
AAT3192-4. By changing the duty cycle of the PWM
signal from 100% (logic high) to 10%, LEDs sink current
can be programmed from 20mA to 2.4mA. To save
power when not used, AAT3192-4 can be shutdown by
holding the EN/PWM pin low for 1ms.
Table 2: AAT3192-2 LED Current Settings.
Dx Output Current (mA)
20.00
Lastly, Table 4 and Figure 5 illustrate the AAT3192-4’s
LED current control profile as a function of a PWM control signal.
15.00
10.00
5.00
0.00
PWM Control (AAT3192-4 only)
1
2
3
4
5
6
7
EN/PWM Duty Cycle
D1-D2 Current (mA)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
20
17.9
15.9
14
12.1
10.1
8.2
6.3
4.3
2.4
8
S2Cwire Interface Data Code
Figure 3: AAT3192-2 Current Control Profile.
Data
EN Rising Edges
D1-D2 Current (mA)
1
2
3
4
1
2
3
4
20
13.3
6.7
0.87
Table 4: AAT3192-4 LED Current Settings
(RSET = 14.3kΩ, fPWM = 50kHz).
20.00
Dx Output Current (mA)
Table 3: AAT3192-3 LED Current Settings.
Dx Output Current (mA)
20.00
15.00
10.00
10.00
5.00
0.00
5.00
0.00
15.00
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
EN/PWM Input Pin Duty Cycle (%)
1
2
3
4
Figure 5: AAT3192-4 Current Control Profile
(RSET = 14.3kΩ, fPWM = 50kHz).
2
S Cwire Interface Data Code
Figure 4: AAT3192-3 Current Control Profile.
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PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Applications Information
Device Switching Noise Performance
LED Selection
The AAT3192 is specifically intended for driving white
LEDs. However, the device design will allow the AAT3192
to drive most types of LEDs with forward voltage specifications ranging from 2.2V to 4.7V. LED applications
may include mixed arrangements for display backlighting, keypad display, and any other application needing a
constant current sink generated from a varying input
voltage. Since the D1 to D2 constant current sinks are
matched with negligible supply 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 AAT3192 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.
Constant Current Setting
The LED current is controlled by the RSET resistor. For
maximum accuracy, a 1% tolerance resistor is recommended. Table 5 shows RSET resistor values for
AAT3192-1/2/4 and Table 6 shows RSET resistor values
for AAT3192-3 for various LED full-scale current levels.
ILED (mA)
RSET (KΩ)
30
25
20
18
15
10
9.53
11.5
14.3
15.8
19.1
28.7
Table 5: Maximum LED Current and RSET Resistor
Values (1% Resistor Tolerance)
for the AAT3192-1/2/4.
ILED (mA)
RSET (KΩ)
30
20
15
10
7.68
11.5
15.4
23.2
Table 6: Maximum LED Current and RSET Resistor
Values (1% Resistor Tolerance)
for the AAT3192-3.
12
The AAT3192 operates at a fixed frequency of approximately 1MHz to control noise and limit harmonics that
can interfere with the RF operation of mobile communication devices. Back-injected noise appearing on the
input pin of the charge pump is 20mV peak-to peak,
typically ten times less than inductor-based DC/DC boost
converter white LED backlight solutions. The AAT3192
soft-start feature prevents noise transient effects associated with inrush currents during start-up of the charge
pump circuit.
Shutdown
Since the current switches are the only power returns for
all loads, there is no leakage current when all sink
switches are disabled. To activate the shutdown operation, the EN/SET input for the AAT3192-1/2/3 should be
strobed low for longer than tOFF (500μs). For the 3192-4
PWM options, shutdown operation is enabled when the
EN/PWM input is strobed low longer than 1ms. In this
state, the AAT3192 typically draws less than 1μA from
the input. 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. Due to the unique circuit architecture and
design of the AAT3192, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT3192 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
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.
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3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
The AAT3192 efficiency may be quantified under very
specific conditions and is dependent upon the input voltage versus the output voltage across the loads applied
to outputs D1 through D2 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.
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=
-or-
⎛ VF ⎞
η (%) = 100 · 2V
⎝ IN⎠
1x Mode Efficiency
The AAT3192 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:
POUT
V ·I
VF
= F LED =
PIN
VIN · 2IOUT 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 consumption, the actual efficiency can be measured at
51%. Efficiency will decrease substantially as load current drops below 1mA or when the voltage level at VIN
approaches the voltage level at VOUT.
Additional Applications
P
V ·I
VF
η = OUT = F LED ≅
PIN
VIN · IOUT
VIN
The current sinks of the AAT3192 can be combined to
drive higher current levels through a single LED. As an
example, a single LED can be driven at 60mA total by
combining together the D1-D2 outputs.
-or-
⎛ VF ⎞
η (%) = 100 · V
⎝ IN⎠
C2
1μF
2x Charge Pump Mode Efficiency
The AAT3192 contains a 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 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=
3192.2008.07.1.3
PF
PIN
1
2
3
4
5
C1
1μF
VIN
C3
1μF
D1
N/C
D1
OUT
D2
CGND
C+ RSET
IN EN/SET
AAT3192
10
9
8
7
6
R1
9.53k
EN/SET
Figure 6: Higher Current, Single LED Application.
For lower-cost applications, the flying capacitor can be
removed. This will force the AAT3192 to operate in 1x
mode. To maintain regulated LED current, the input
supply voltage has to be higher than the charge-pump’s
dropout voltage in 1x mode.
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13
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
C2
1μF
D1
lowest cost, has a smaller PCB footprint, and is non-polarized. Low ESR ceramic capacitors help maximizing
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
D2
U1
1
2
3
4
5
VIN
C3
1μF
N/C
D1
D2
OUT
GND
CC+ RSET
IN EN/SET
AAT3192
10
9
8
7
6
Equivalent Series Resistance
R1
9.53k
EN/SET
Figure 7: Lower Cost 1x Mode Application.
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
Ceramic composition capacitors are highly recommended
over all other types of capacitors for use with the
AAT3192. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is
14
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 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
AAT3192 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.
www.analogictech.com
3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Evaluation Board Schematic
3
2
DC+
1
DC-
C2
1μF
VIN
J1
D1
D2
JPx
GND
JP5 C1
1μF
1
2
3
4
5
C3
1μF
N/C
D1
OUT
D2
CGND
C+
RSET
IN EN/SET
U1
10
9
8
7
6
R1
9.53k
AA T3192
GND
GND
R7
220
J2
R6
100K
VIN
GND
R3 R2 R1
1K 1K 1K
CYCLE
0
2
4
SW3
1
3
5
UP
0
2
4
DOWN
0
2
4
SW2
1
3
5
U2
1
2
3
4
VDD
GP5
GP4
GP3
VSS
GP0
GP1
GP2
PIC12F675
VR4
POT10K
8
7
6
5
C5
1μF
R5
330
LED7
RED
R4
330
GND
GND
SW1
1
3
5
LED0
GRN
GND
GND
3192.2008.07.1.3
www.analogictech.com
15
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Evaluation Board Layout1
Figure 8: AAT3192 Evaluation Board
Component Side Layout.
Figure 9: AAT3192 Evaluation Board
Solder Side Layout.
1. The AAT3193 Evaluation Board is also used for the AAT3192; for the AAT3192, LED diodes D2 = D1, D3 = D2, and D1 is not connected.
16
www.analogictech.com
3192.2008.07.1.3
PRODUCT DATASHEET
AAT3192
ChargePump
2-Channel Charge-Pump LED Driver
TM
Ordering Information
Package
Interface
Current Control, Inverting
Marking
Part Number (Tape and Reel)
SC70JW-10
SC70JW-10
SC70JW-10
SC70JW-10
S2Cwire
S2Cwire
S2Cwire
PWM
16-step
8-step
4-step
Linear
ZYXYY
AAT3192IJQ-1-T1
AAT3192IJQ-2-T1
AAT3192IJQ-3-T1
AAT3192IJQ-4-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.
3192.2008.07.1.3
www.analogictech.com
17
PRODUCT DATASHEET
AAT3192
ChargePump
2-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.
18
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3192.2008.07.1.3