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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers General Description
The AAT3192 and AAT3193 are charge-pump based, current-sink white LED drivers capable of driving one to three LEDs up to 30mA, each. They automatically switch between 1x mode and 2x mode to maintain the highest efficiency and optimal LED current accuracy and matching. The AAT3192/93 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 and the AAT3193 are available in a 2x2mm 10-lead SC70JW-10 packages.
Features
* * * *
ChargePumpTM
* * * * * *
Drives up to 3 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 * AAT3192/93-1: 16-step * AAT3192/93-2: 8-step * AAT3192/93-3: 4-step -- ON/OFF or PWM Interface * AAT3192/93-4 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
* * * * Low-cost Low-cost Low-cost Low-cost Cordless Phone Handsets Digital Cameras Mobile Phone Handsets MP3 and PMP Players
Typical Application
Input Voltage 2.7V to 5.5V C IN 1F
IN C+ OUT
Input Voltage 2.7V to 5.5V C IN 1F
IN C+ OUT
CP 1F
AAT3192-1
CEN/SET RSET GND D1 D2
C OUT 1F
CP 1F
AAT3193-1
C-
COUT 1F WLEDs OSRAM LW M 678 or equivalent
EN/SET S 2Cwire Interface R SET 14.3k
WLEDs OSRAM LW M 678 or equivalent
EN/SET S 2Cwire Interface
EN/SET
D1 D2
RSET GND
D3
RSET 14.3k
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Pin Descriptions
Symbol Pin
1
AAT3192 AAT3193
Description
AAT3192: No connection. AAT3193: 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 GND with a 1F or larger ceramic capacitor. Charge pump capacitor negative node. Charge pump capacitor positive node. Connect a 1F ceramic capacitor between C+ and C-. Power source input. Connect IN to the power source, typically the battery. Bypass IN to GND with a 1F 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 AAT3192/93-1/-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 AAT3192/93-4. 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 AAT3192/93-1/-2/-4, a 14.3k resistor sets each full-scale output current to 20mA, maximum. For the AAT3192/93-3, a 10.7k resistor is recommended. Ground. Connect this pin to the system's ground plane. AAT3192: LED2 Current Sink Input. D2 is the input of LED2 current sink. Connect LED2's anode to OUT and its cathode to D2. AAT3193: LED3 Current Sink Input. D3 is the input of LED3 current sink. Connect LED3's anode to OUT and its cathode to D3. AAT3192: LED1 Current Sink Input. D1 is the input of LED1 current sink. Connect LED1's anode to OUT and its cathode to D1. AAT3193: LED2 Current Sink Input. D2 is the input of LED2 current sink. Connect LED2's anode to OUT and its cathode to D2.
N/C
D1
2 3 4 5
OUT CC+ IN EN/SET (AAT3192/93-1/ -2/-3)
6 EN/PWM (AAT3192/93-4)
7
RSET
8
GND
9
D2
D3
10
D1
D2
Pin Configuration
AAT3192 SC70JW-10 (Top View)
N/C OUT CC+ IN
1 2 3 4 5 10 9 8 7 6
AAT3193 SC70JW-10 (Top View)
D1 D2 GND RSET EN/SET D1 OUT CC+ IN
1 2 3 4 5 10 9 8 7 6
D2 D3 GND RSET EN/SET
2
3193.2007.05.1.0
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Part Number Descriptions
Part Number
AAT3192IJQ-1 AAT3192IJQ-2 AAT3192IJQ-3 AAT3192IJQ-4 AAT3193IJQ-1 AAT3193IJQ-2 AAT3193IJQ-3 AAT3193IJQ-4
Interface
S2Cwire S2Cwire S2Cwire PWM S2Cwire S2Cwire S2Cwire PWM
Current Control, Inverting
16-step 8-step 4-step Linear 16-step 8-step 4-step Linear
Absolute Maximum Ratings1
Symbol Description
IN, C+, C-, OUT, D1, D2, D3, 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
-0.3 to 6.0 -0.3 to VIN + 0.3 -40 to 150 300
Units
V V C C
Thermal Information
Symbol
PD JA
Description
Maximum Power Dissipation Maximum Thermal Resistance2
2, 3
Value
625 160
Units
mW 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 40C ambient temperature. 3193.2007.05.1.0
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Electrical Characteristics1
IN = EN = 3.6V; CIN = 1F; COUT = 1F; CCP = 1F; RSET = 14.3k; TA =-40C to 85C unless otherwise noted. Typical values are at TA = 25C. Symbol Description Conditions Min
2.7 EN = IN, ID1 = ID2 = ID3 = OFF (WLED Test Mode) EN = IN, ID1 = ID2 = ID3 = FS Operating, ID1 = ID2 = ID3= OPEN; IN = 5V EN/SET or EN/PWM = GND 100 0.9 115 150 19.6 3 1.3 1.3 2.5 150
Typ
Max
5.5 5 1.5 4.5 1
Units
V mA mA mA A mA MHz mV s mA % mA mA mA mV
Input Power Supply IN Input Voltage Range
IIN
Input Operating Current
IIN(SHDN) Input Shutdown Current Charge Pump Section IOUT OUT Maximum Output Current fOSC Charge Pump Oscillator Frequency VIN_(TH) Charge Pump Mode Hysteresis tOUT Output Start-Up Time AAT3192/93-1/-2/-4: LED Current Sink Outputs ID_(MAX) D1 - D3 Current Accuracy ID_(MAX) D1 - D3 Current Matching D1 - D3 Current Accuracy ID_(DATA15) (AAT3192/93-1 only) D1 - D3 Current Accuracy ID_(DATA8) (AAT3192/93-2 only) D1 - D3 Current Accuracy ID_(10%) (AAT3192/93-4 only) D1- D3 Charge Pump Mode VD_(TH) Transition Threshold
0.65 ID1 = ID2 = ID3= 20mA EN/SET or EN/PWM = IN DATA = 1; VIN - VF = 1.5V DATA = 1; VIN - VF = 1.5V DATA = 15; VIN - VF = 1.5V DATA = 8; VIN - VF = 1.5V DC = 10%; VIN - VF = 1.5V ID1 = ID2 = ID3 = 20mA 17.6
1.15 250
21.6
1.0 1.0
1.56 1.56
1. The AAT3192/93 are guaranteed to meet performance specification over the -40C to 85C operating temperature range and are assured by design, characterization and correlation with statistical process controls.
4
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Electrical Characteristics1
IN = EN = 3.6V; CIN = 1F; COUT = 1F; CCP = 1F; RSET = 14.3k; TA =-40C to 85C unless otherwise noted. Typical values are at TA = 25C. Symbol Description Conditions
RSET = 10.7k; DATA = 1; VIN - VF = 1.5V RSET = 10.7 k; DATA = 1; VIN - VF = 1.5V RSET = 10.7k; DATA = 4; VIN - VF = 1.5V RSET = 10.7k; ID1 = ID2 = ID3 = 20mA
Min
Typ
Max
Units
AAT3192/93-3: LED Current Sink Outputs ID_(MAX) ID_(MAX) ID_(DATA4) VD_(TH) D1 - D3 Current Accuracy D1 - D3 Current Matching D1 - D3 Current Accuracy 17.6 19.6 3 0.72 0.9 150 1.1 21.6 mA % mA mV
D1- D3 Charge Pump Mode Transition Threshold AAT3192/93-1/-2/-3: EN/SET and S2Cwire Control VENH EN Input High Threshold Voltage 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 AAT3192/93-4: EN/PWM Current Control VENH EN/PWM Input High Threshold Voltage VENL 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
1.4 EN/SET = IN = 5V -1 0.4 1 500 500 75 50 75 1.4 EN/PWM = IN = 5V -1 2 0.15 Duty Cycle = 80% 1 50 0.4 1
0.3
V V A s s s ns s V V A s ms kHz
1. The AAT3192/93 are guaranteed to meet performance specification over the -40C to 85C operating temperature range and are assured by design, characterization and correlation with statistical process controls. 3193.2007.05.1.0
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Typical Characteristics
Operating Current (No Load) vs. Input Voltage
3.60 3.50 3.40
0.010 0.008
Shutdown Current vs. Temperature
IQ (mA)
85C 25C
IIN(SHDN) (A)
0.006 0.004 0.002 0.000 -40
3.30 3.20 3.10 3.00
-45C
2.7 3.1 3.5 3.9 4.3
0C
4.7 5.1 5.5
-15
10
35
60
85
VIN (V)
Temperature (C)
Efficiency vs. Input Voltage
100% 90% 80% 21.0 20.5
Current Matching vs. Temperature
D2
Efficiency (%)
70% 60% 50% 40% 30% 20% 10% 0% 2.7 3.1
Current (mA)
20.0 19.5 19.0 18.5 18.0 -40
30mA VF = 3.8V 10mA VF = 3.2V
3.5 3.9
20mA VF = 3.5V
4.3 4.7 5.1 5.5
D3 D1
-15 10 35 60 85
Input Voltage (V)
Temperature (C)
Turn On to 2X Mode
(20mA/ch)
Turn Off from 2X Mode
(20mA/ch)
EN/SET (2V/div) VOUT (2V/div) VSINK (2V/div) IIN (200mA/div)
EN/SET (2V/div) VOUT (1V/div)
IIN (200mA/div)
Time (200s/div)
Time (200s/div)
6
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Typical Characteristics
Turn On to 1X Mode
(VIN = 4.2V; 20mA/ch)
32
Maximum LED Current vs RSET
EN/SET (2V/div)
ILED (mA)
28 24 20 16 12 8 4 0 8 13 18 23 28 33
VF (2V/div) VSINK (2V/div) IIN (200mA/div)
Time (200s/div)
RSET (k)
EN Input High Threshold Voltage vs. Input Voltage
1.2 1.0 1.2 1.0
EN Input Low Threshold Voltage vs. Input Voltage
VENH (V)
0.8 0.6 0.4 0.2 2.7
25C 85C
-40C
VENL (V)
0.8 0.6 0.4 0.2
-40C 85C
2.7 3.1 3.5 3.9 4.3
25C
3.1
3.5
3.9
4.3
4.7
5.1
5.5
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
EN/SET Input Latch Timeout vs. Input Voltage
350 300
EN/SET Input OFF Timeout vs. Input Voltage
350
85C
TEN/SET(OFF) (s)
85C
300 250 200 150 100 2.7
TEN/SET(LAT) (s)
250 200 150 100 2.7
25C -40C
25C -40C
3.1
3.5
3.9
4.3
4.7
5.1
5.5
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Typical Characteristics
Transition of LED Current
(20mA to 1.3mA) EN (2V/div) VOUT (1V/div) VSINK (1V/div) IIN (50mA/div)
4.0V
Transition of LED Current
(1.3mA to 20mA) EN (2V/div) VOUT (1V/div)
4.2V
0.5V
VSINK (1V/div) IIN (50mA/div)
1.5V
Time (100s/div)
Time (100s/div)
Output Ripple Waveform
(2X Mode; 20mA Load) VIN (AC Coupled) (20mV/div) VOUT (AC Coupled) (20mV/div) VSINK (AC Coupled) (50mV/div)
200 180
Input Current vs. Input Voltage
VIN Falling VIN Rising
Input Current (mA)
160 140 120 100 80 60 40 20 0
ILED = 30mA
ILED = 20mA
ILED = 10mA
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
Time (1s/div)
Input Voltage (V)
8
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Functional Block Diagram
C+ C- OUT
IN
Two-Mode CP Control
3
D1 D2
VF Monitoring
D3
GND
IREF
EN/SET (EN/PWM)
S2Cwire Control (PWM Control)
DAC
RSET
Functional Description
The AAT3192 and AAT3193 are low-cost chargepump solutions designed to drive up to three 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 AAT3192/93 requires only four external components: one 1F ceramic capacitor for the charge pump flying capacitors (CP), one 1F ceramic input capacitor (CIN), one 1F ceramic output capacitor (COUT) and a resistor (RSET) to set the maximum LED current. The three constant current outputs of
AAT3193 (D1 to D3) can drive three individual LEDs with a maximum current of 30mA each. AAT3192 can drives two constant output sinks (D1 and D2) with up to 30mA maximum current each. AnalogicTech's S2Cwire serial Interface enables the AAT3192/93-1/ -2/-3 and changes the current sink magnitudes through the EN/SET pin. The AAT3192/93-4 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 14.3k external resistor at the RSET pin, the AAT3192/93-1/-2/-4 includes an integrated serial LED current control that sets the full-scale LED current between 20mA and 0.63mA. For the AAT3192/93-3, a 10.7k external resistor at the RSET pin sets the fu ll-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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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers
S2Cwire Serial Interface (AAT3192/93-1/-2/-3 only)
The LED output current of AAT3192/93 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
THI TLO TLAT TOFF
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 AAT3192/93 enters into shutdown mode and draws less than 1A from the input and the internal data register is reset to zero. The AAT3192/93-1/2/3's serial interface reduces the LED current on each rising pulse of the enable input. If the AAT3192/93 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 AAT3192/93-1. For the AAT3192/93-2, Table 2 and Figure 3 illustrate an 8-step LED current control profile. For the AAT3192/93-3, Table 3 and Figure 4 illustrate a 4-step LED current control profile.
EN/SET
1 2 n-1 n 16
Data Reg
0
n-1
0
Figure 1. S2C Serial Interface Timing
20.00
Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Dx Output Current (mA)
EN Rising Edges
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
D1-D3 Current (mA)
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
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: AAT3192/93-1 Current Control Profile
Table 1: AAT3192/93-1 LED Current Settings 10
3193.2007.05.1.0
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers
20.00
Data
1 2 3 4 5 6 7 8
Dx Output Current (mA)
EN Rising Edges
1 2 3 4 5 6 7 8
D1-D3 Current (mA)
20 17.3 14.7 12 9.3 6.7 4 1.3
15.00
10.00
5.00
0.00
1
2
2
3
4
5
6
7
8
S Cwire Interface Data Code
Table 2: AAT3192/93-2 LED Current Settings
Figure 3: AAT3192/93-2 Current Control Profile
Data
1 2 3 4
Dx Output Current (mA)
EN Rising Edges
1 2 3 4
D1-D3 Current (mA)
20 13.3 6.7 0.87
20.00
15.00
10.00
5.00
Table 3: AAT3192/93-3 LED Current Settings
0.00
1
2
2
3
4
S Cwire Interface Data Code
Figure 4: AAT3192/93-3 Current Control Profile
PWM Control (AAT3192/93-4 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 into the EN/PWM pin of the AAT3192/93-4. 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, AAT3192/93-4 can be shutdown by holding the EN/PWM pin low for 1ms. Lastly, Table 4 and Figure 5 illustrate the AAT3192/93-4's LED current control profile as a function of a PWM control signal.
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AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Applications Information
LED Selection
The AAT3192/93 is specifically intended for driving white LEDs. However, the device design will allow the AAT3192/93 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 D3 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 AAT3192/93 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.
EN/PWM Duty Cycle
100% 90% 80% 70% 60% 50% 40% 30% 20% 10%
D1-D3 Current (mA)
20 17.9 15.9 14 12.1 10.1 8.2 6.3 4.3 2.4
Table 4: AAT3192/93-4 LED Current Settings
20.00
Dx Output Current (mA)
15.00
10.00
5.00
Constant Current Setting
90% 80% 70% 60% 50% 40% 30% 20% 10%
0.00 100%
EN/PWM Input Pin Duty Cycle (%)
The LED current is controlled by the RSET resistor. For maximum accuracy, a 1% tolerance resistor is recommended. Table 5 shows the RSET resistor value for AAT3193-1/2/4 for various LED full-scale current levels. ILED (mA)
30 20 15 10
Figure 5: AAT3192/93-4 Current Control Profile
RSET (K)
9.53 14.3 19.1 28.7
Table 5: Maximum LED Current and RSET Resistor Values (1% Resistor Tolerance) for the AAT3193-1/2/4.
Device Switching Noise Performance
The AAT3192/93 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 AAT3192/93 soft-start feature prevents noise transient effects 12
3193.2007.05.1.0
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers
associated with inrush currents during start-up of the charge pump circuit. Each of these modes will yield different efficiency values. Refer to the following two sections for explanations for each operational mode.
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 AAT3192/93-1/2/3 should be strobed low for longer than tOFF (500s). For the 3192/93-4 PWM options, shutdown operation is enabled when the EN/PWM input is strobed low longer than 1ms.In this state, the AAT3192/93 typically draws less than 1A from the input. Registers are reset to 0 in shutdown.
1X Mode Efficiency
The AAT3192/93 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 () in 1X charge-pump mode can be expressed as:
= V *I VF POUT = F LED PIN VIN * IOUT VIN
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 AAT3192/93, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the AAT3192/93 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. The AAT3192/93 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 D3 (or D2 in the case of the AAT3192) 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.
3193.2007.05.1.0
-or VF (%) = 100 * V IN
2X Charge Pump Mode Efficiency
The AAT3192/93 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 () 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 () for an ideal 2X charge pump can typically be expressed as the output power divided by the input power.
=
PF 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 () can be rewritten as:
= V *I VF POUT = F LED = PIN VIN * 2IOUT 2VIN
-or VF (%) = 100 * 2V IN
For a charge pump with an output of 5V and a nominal input of 3.5V, the theoretical efficiency is 71%. 13
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers
Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 90%. Efficiency will decrease substantially as load current drops below 1mA or when the voltage level at VIN approaches the voltage level at VOUT. formance. 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.
Additional Applications
The current sinks of the AAT3192 and the AAT3193 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-D3 outputs.
C2 1F D1
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3192/93. 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 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.
VIN
C1 1F
1 2 3 4 5
D1 D2 OUT D3 CGND C+ RSET IN EN/SET
AAT3193
10 9 8 7 6
C3 1F
R1 14.3k
EN/SET
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.
Figure 6: Higher Current, Single LED Application. For lower-cost applications, the flying capacitor can be removed. This will force AAT3192/93 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.
C2 1F D1 D2 D3
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 composed 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 AAT3192/93 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.
U1
1 2 3 4 5
VIN
D2 D1 D3 OUT GND CC+ RSET IN EN/SET
AAT3193
10 9 8 7 6
C3 1F
R1 14.3k
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 per14
3193.2007.05.1.0
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers
Evaluation Board Schematic
DCDC+
1 2 3
VIN J1 C2 1F D1 D2 D3 JPx
GND
JP5 C1 1F
1 2 3 4 5
D1 D2 OUT D3 CGND C+ RSET IN EN/SET
U1 AA T3193
10 9 8 7 6
C3 1F
R1 14.3k
GND
GND
R7 220 J2 R6 100K
VIN GND
R3 R2 R1 1K 1K 1K CYCLE UP
0 2 4 1 3 5 0 2 4
U2
1 2 3 4
SW3
1 3 5
VDD GP5 GP4 GP3
VSS GP0 GP1 GP2
8 7 6 5
VR4 POT10K
C5 1F
R5 330 LED7 RED
SW2 SW1
1 3 5
PIC12F675
DOWN
R4 330
GND
GND
0 2 4
LED0 GRN
GND GND
Evaluation Board Layout
Figure 8: AAT3193 Evaluation Board Top Side Layout.
3193.2007.05.1.0
Figure 9: AAT3193 Evaluation Board Bottom Side Layout. 15
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Ordering Information
Package
SC70JW-10 SC70JW-10 SC70JW-10 SC70JW-10 SC70JW-10 SC70JW-10 SC70JW-10 SC70JW-10
Interface
S2Cwire S2Cwire S2Cwire PWM S2Cwire S2Cwire S2Cwire PWM
Current Control, Inverting
16-step 8-step 4-step Linear 16-step 8-step 4-step Linear
Marking
Part Number (Tape and Reel)
AAT3192IJQ-1-T1 AAT3192IJQ-2-T1 AAT3192IJQ-3-T1 AAT3192IJQ-4-T1 AAT3193IJQ-1-T1 AAT3193IJQ-2-T1 AAT3193IJQ-3-T1 AAT3193IJQ-4-T1
XGXYY
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/pbfree.
1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.
16
3193.2007.05.1.0
AAT3192/93
Low-Cost, 2-/3-Channel Charge-Pump LED Drivers Package Information
SC70JW-10
0.40 BSC
1.75 0.10
0.225 0.075
Top View
2.00 0.20
2.20 0.20
0.85 0.15
1.10 MAX
0.15 0.05
0.100
0.45 0.10 2.10 0.30
4 4
7 3
Side View
All dimensions in millimeters.
End View
(c) 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737- 4600 Fax (408) 737- 4611
3193.2007.05.1.0
0.05 0.05
17

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