AAT3103IJQ-2-T1

PRODUCT DATASHEET AAT3103 ChargePumpTM General Description The AAT3103 is a constant frequency charge-pump based current-source white LED driver capable of driving one to three LEDs up to 30mA, each. The charge pumps automatically switch between 1x mode and 2x mode to maintain the highest efficiency and optimal LED current accuracy and matching. A low external parts count (one 1μF flying capacitor, two small 1μF capacitors at IN and OUT and one current setting resistor) makes the AAT3103 ideally suited for small battery-powered applications. The AAT3103-1/-2 uses AnalogicTech's Simple Serial Control™ (S2Cwire™) interface to enable, disable, and program the LED driving current. The AAT3103-4 employs a Pulse Width Modulation (PWM) signal with up to 50kHz frequency, 10% to 100% duty cycle to program the LED current. A low-current shutdown feature disconnects the load from IN and reduces quiescent current to less than 1μA. Built-in soft-start circuitry prevents excessive inrush current during start-up. Integrated short circuit and thermal protection circuitry protects the device from damage. The AAT3103 is available in a 2x2.1mm thermally enhanced Pb-free 10-lead SC70JW-10 package. 3-Channel Charge-Pump LED Driver Features • • • • Source WLED Driver, up to 3 LEDs at up to 30mA, each Automatic Switching Between 1x and 2x Modes 900KHz Switching Frequency Linear LED Output Current Control ▪ Single-wire, S2Cwire Interface AAT3103-1: 16-step AAT3103-2: 8-step ON/OFF or PWM Interface ▪ AAT3103-4 ±10% LED Output Current Accuracy ±3% LED Output Current Matching Low-current Shutdown Mode Built-in Short Circuit and Thermal Protection Automatic Soft-start 2x2.1mm SC70JW-10 Package • • • • • • Applications • • • • Cordless Phone Handsets Mobile Phone Handsets MP3 and PMP Players Digital Cameras Typical Application Input Voltage 2.7V to 5.5V C IN 1μF IN C+ OUT CP 1μF AAT3103-1 C- C OUT 1μF EN/SET S2Cwire Interface EN/SET D1 D2 RSET D3 RSET 14.3kΩ AGND WLEDs OSRAM LW M 678 or equivalent 3103.2008.03.1.0 www.analogictech.com 1 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Pin Descriptions Pin # 1 2 3 4 5 3-Channel Charge-Pump LED Driver Symbol D1 OUT CC+ IN EN/SET (AAT3103-1/-2) Description LED1 Current Source Output. Connect LED1’s anode to D1 and its cathode to AGND. Charge Pump Output. Bypass OUT to AGND 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 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 AAT3103-1/-2 to control the LED brightness up to the maximum current set by RSET. LED ON/OFF and PWM (Pulse Width Modulation) control input. This logic input controls the LED outputs for the AAT3103-4. A PWM signal, ranging from 10% to 100% duty cycle, controls the LED current linearly between minimum and the full-scale output set by RSET. A 1% tolerance resistor from this pin to AGND sets the maximum LED current value. For optimal LED output current accuracy and matching in the AAT3103-1/-2/-4, a 14.3kΩ resistor sets each full-scale output current to 20mA. Analog Ground. Connect this pin to the system’s analog ground plane. LED3 Current Source Output. Connect LED3’s anode to D3 and its cathode to AGND. LED2 Current Source Output. Connect LED2’s anode to D2 and its cathode to AGND. 6 EN/PWM (AAT3103-4) RSET AGND D3 D2 7 8 9 10 Pin Configuration SC70JW-10 (Top View) D1 OUT CC+ IN 1 10 D2 D3 AGND RSET EN/SET (EN/PWM) 2 3 4 5 9 8 7 6 2 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Absolute Maximum Ratings1 Symbol Description IN, C+, C-, OUT, D1, D2, D3, and RSET Pin Voltages to AGND EN/SET or EN/PWM Pin Voltage to AGND Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec) 3-Channel Charge-Pump LED Driver Value -0.3 to 6.0 -0.3 to VIN + 0.3 -40 to 150 300 Units V V °C °C TJ TLEAD Thermal Information Symbol PD ΘJA 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 40 °C ambient temperature. 3103.2008.03.1.0 www.analogictech.com 3 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM 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 Min 2.7 IN = 5.5V; EN = IN; VD1 = VD2 = VD3 = 0V IN = 5.5V; EN = IN; ID1 = ID2 = ID3 = FS, excluding ID1-ID3; VD1 = VD2 = VD3 = IN – 1.5V Operating, ID1 = ID2 = ID3 = OPEN EN/SET or EN/PWM = GND 7.4 1.9 4 3-Channel Charge-Pump LED Driver Typ Max 5.5 10 3 6.8 1 Units V mA μA mA MHz mV μs mA % mA mA mA mV 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 ID1 = ID2 = ID3 = 20mA tOUT LED Output Current Start-up Time EN/SET or EN/PWM = IN AAT3103-1/-2/-4: LED Current Source Outputs ID_(MAX) D1 - D3 Current Accuracy DATA = 1; VIN – VF = 1.5V. ΔID_(MAX) D1 - D3 Current Matching DATA = 1; VIN – VF = 1.5V D1 - D3 Current Accuracy ID_(DATA15) DATA = 15; VIN – VF = 1.5V (AAT3103-1 only) D1 - D3 Current Accuracy ID_(DATA8) DATA = 8; VIN – VF = 1.5V (AAT3103-2 only) D1 - D3 Current Accuracy DC = 10%; VIN – VF = 1.5V ID_(10%) (AAT3103-4 only) D1- D3 Charge Pump Mode VD_(TH) ID1 = ID2 = ID3 = 20mA Transition Threshold VSET RSET Pin Voltage AAT3103-1/-2: EN/SET and S2Cwire Control VENH EN/SET Input High Threshold Voltage VENL EN/SET Input Low Threshold Voltage IEN(LKG) EN/SET Input Leakage Current EN/SET = IN = 5V 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 AAT3103-4: 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 EN/PWM = IN = 5V PWM Control Turn-on Delay tPWM(ON) tEN/PWM EN/PWM Input OFF Timeout fPWM PWM Control Frequency Duty cycle = 80% 0.65 100 0.9 325 150 20 ±3 1.34 1.34 2.5 280 1.4 18 1.0 1.0 22 1.61 1.61 1.14 1.4 -1 1.18 1.22 V V V μA μs μs μs ns μs V V μA μs ms kHz 0.3 50 0.4 1 500 500 75 75 1.4 -1 110 0.15 1 50 0.4 1 1. The AAT3103 is guaranteed to meet performance specifications over the -40°C to 85°C operating temperature range and is assured by design, characterization and correlation with statistical process controls. 4 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Typical Characteristics Shutdown Current vs. Temperature 0.07 0.06 0.05 8.0 7.0 6.0 3-Channel Charge-Pump LED Driver Operating Current vs. Input Voltage (VD1 = VD2 = VD3 = 0V) ISHDN (µA) 0.04 0.03 0.02 0.01 0.00 -40 -15 10 35 IQ (mA) 5.0 4.0 3.0 2.0 VIN = 5.5V VIN = 2.7V 60 85 1.0 0.0 2.5 3 3.5 4 4.5 5 -40°C 25°C 85°C 5.5 Temperature (°C) Input Voltage (V) Operating Current vs. Input Voltage (No Load; D1, D2, D3 Open) 4.2 LED Current Matching vs. Temperature 21.0 3.9 Current (mA) 4.1 20.5 IQ (mA) 20.0 3.8 3.6 2.5 85°C 25°C -40°C 3 3.5 4 4.5 5 5.5 19.5 19.0 -40 D1 D2 D3 -15 10 35 60 85 Input Voltage (V) Temperature (°C) Efficiency vs. Input Voltage 100 90 80 28 35 ILED Full Scale vs. RSET Efficiency (%) 70 ILED (mA) ILED = 30mA,VF = 3.5V ILED = 20mA,VF = 3.2V ILED = 10mA,VF = 3.0V 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 60 50 40 30 20 10 0 21 14 7 0 8 13 18 23 28 33 Input Voltage (V) RSET (kΩ) 3103.2008.03.1.0 www.analogictech.com 5 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Typical Characteristics EN Input High Threshold Voltage vs. Input Voltage 1.2 1.0 1.2 1.0 3-Channel Charge-Pump LED Driver EN Input Low Threshold Voltage vs. Input Voltage VENH (V) 0.6 0.4 0.2 2.7 VENL (V) -40°C 25°C 85°C 3.1 3.5 3.9 4.3 4.7 5.1 5.5 0.8 0.8 0.6 0.4 0.2 2.7 -40°C 25°C 85°C 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) EN/SET Input Latch Timeout vs. Input Voltage 350 300 400 350 EN/SET Input Off Timeout vs. Input Voltage tEN/SET(OFF) (V) tEN/SET(LAT) (V) 250 200 150 100 2.7 300 250 200 150 100 2.7 85°C 25°C -40°C 3.1 3.5 3.9 4.3 4.7 5.1 5.5 85°C 25°C -40°C 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) Turn-On to 2X Mode (VIN = 3.6V; 20mA/Dx) Turn-Off from 2X Mode (VIN = 3.6V; 20mA/Dx) EN/SET (2V/div) VOUT (5V/div) VD1 (2V/div) IIN (200mA/div) 0V 4.2V 3.2V EN/SET (2V/div) VD1 (2V/div) 0V 2.7V 0V 0A IIN (200mA/div) Time (200µs/div) 0A Time (100µs/div) 6 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Typical Characteristics Turn-On to 1X Mode (VIN = 4.2V; 20mA/Dx) 3-Channel Charge-Pump LED Driver Output Ripple Waveform (2X Mode; 20mA/Dx) EN/SET (2V/div) VOUT (2V/div) VD1 (2V/div) IIN (200mA/div) 0V VOUT (AC) (20mV/div) VIN (20mV/div) VD1 (20mV/div) 0V 0V 0V 0V 0V 0A Time (200µs/div) Time (1µs/div) LED Current Transition (VIN = 4.2V; 1.3mA to 20mA) LED Current Transition (VIN = 4.2V; 20mA to 1.3mA) EN/SET (2V/div) VOUT (2V/div) VD1 (2V/div) IIN (50mA/div) 0V EN/SET (2V/div) 4.2V 3.2V 0V 4.2V 3.2V VOUT (2V/div) VD1 (2V/div) IIN (50mA/div) 0A 2.7V 2.7V 0A Time (100µs/div) Time (100µs/div) Input Current vs. Input Voltage 250 Input Current (mA) 200 150 100 50 0 ILED = 30mA ILED = 20mA ILED = 10mA VIN Rising VIN Falling 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) 3103.2008.03.1.0 www.analogictech.com 7 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Functional Block Diagram C+ C– OUT 3-Channel Charge-Pump LED Driver IN Two-Mode CP Control 3 D1 D2 VF Monitoring D3 AGND IREF EN/SET (EN/PWM) S2Cwire Control (PWM Control) DAC RSET Functional Description The AAT3103 is a low-cost charge-pump solution designed to drive up to three WLEDs. 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 sources powered from the output of the charge pump. Low 1x charge-pump output resistance and low-drop voltage current sources 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 3.2V with 20mA LED current. 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 AAT3103 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 (RSET) to set the maximum LED current. The three constant current outputs of the AAT3103 (D1 to D3) can drive three individual LEDs with a maximum current of 30mA each. AnalogicTech’s S2Cwire serial interface enables the AAT3103-1/-2 and changes the current source magnitudes through the EN/SET pin. The AAT3103-4 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. With a 14.3kΩ external resistor at the RSET pin, the AAT3103 includes an integrated serial LED current control that sets the full-scale LED current between 20mA and 0.67mA. The full-scale LED current can be set higher or lower than 20mA; see Table 4. For maximum accuracy, a 1% tolerance resistor is recommended. 8 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 ChargePumpTM Part Number Descriptions Part Number AAT3103IJQ-1 AAT3103IJQ-2 AAT3103IJQ-4 3-Channel Charge-Pump LED Driver 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 source outputs. When EN/SET is held low for an amount of time longer than tOFF (500μs), the AAT3103 enters into shutdown mode and draws less than 1μA from the input and the internal data register is reset to zero. The AAT3103-1/-2’s serial interface reduces the LED current on each rising pulse of the enable input. If the AAT3103 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 AAT3103-1. For the AAT3103-2, Table 2 and Figure 3 illustrate an 8-step LED current control profile. . Interface S2Cwire S2Cwire PWM Current Control, Inverting 16-step 8-step Linear S2Cwire Serial Interface (AAT3103-1/-2 only) The LED output current of the AAT3103-1/-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 the 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 THI TLO TLAT TOFF EN/SET 1 2 n-1 n ≤ 16 Data Reg 0 n-1 0 Figure 1: S2Cwire Serial Interface Timing. S2C Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 EN Rising Edges 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 D1-D3 Current (mA) 20.1 18.8 17.5 16.1 14.8 13.4 12.1 10.7 9.4 8.1 6.7 5.4 4.0 2.7 1.34 0.67 Dx LED Current (mA) 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 S2C Wire Interface Data Code Figure 2: AAT3103-1 Current Control Profile, RSET = 14.3kΩ. Table 1: AAT3103-1 LED Current Settings, RSET = 14.3kΩ. 3103.2008.03.1.0 www.analogictech.com 9 PRODUCT DATASHEET AAT3103 ChargePumpTM Data 1 2 3 4 5 6 7 8 3-Channel Charge-Pump LED Driver D1-D3 Current (mA) 20.1 17.5 14.8 12.1 9.4 6.7 4.0 1.34 EN Rising Edges 1 2 3 4 5 6 7 8 cycle of the PWM signal from 100% (logic high) to 10%, the LED current can be programmed from 20mA to 2.6mA. To save power when not used, the AAT3103-4 can be shut down by holding the EN/PWM pin low for 500μs. Lastly, Table 3 and Figure 4 illustrate the AAT3103-4’s LED current control profile as a function of a PWM control signal. EN/PWM Duty Cycle 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% D1-D3 Current (mA) 20.2 18.2 16.2 14.3 12.3 10.4 8.5 6.55 4.6 2.6 Table 2: AAT3103-2 LED Current Settings, RSET = 14.3kΩ. 25 Dx LED Current (mA) 20 15 10 5 0 Table 3: AAT3103-4 LED Current Settings, RSET = 14.3kΩ, fPWM = 25kHz. 1 2 2 3 4 5 6 7 8 S C Wire Interface Data Code Dx LED Current (mA) 25 20 15 10 5 0 100 Figure 3: AAT3103-2 Current Control Profile, RSET = 14.3kΩ. PWM Control (AAT3103-4 only) PWM (Pulse Width Modulation) is a technique of controlling LED brightness by modulating the conduction duty cycle of the LED current. LED brightness is determined by the PWM duty cycle and FS (Full Scale) and LSB (the least LED current). The FS LED current is determined by RSET. The LSB LED current value is equal to the FS value divided by 30. A PWM control signal can be applied into the EN/PWM pin of the AAT3103-4. By changing the duty 90 80 70 60 50 40 30 20 10 PWM Duty Cycle (%) Figure 4: AAT3103-4 Current Control Profile, RSET = 14.3kΩ, fPWM = 25kHz. 10 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 ChargePumpTM Applications Information LED Selection The AAT3103 is specifically intended for driving WLEDs. However, the device design will allow the AAT3103 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 sources are matched with negligible supply voltage dependence, the constant current channels will be matched regardless of the specific LED forward voltage (VF) levels. The internal charge pump and low dropout current sources in the AAT3103 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. Dx LED Current (mA) 3-Channel Charge-Pump LED Driver 35 30 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 RSET = 9.53k RSET = 14.3k RSET = 19.1k RSET = 28.7k S2C Wire Interface Data Code Figure 5: AAT3103-1 LED Current Control Profile at Different RSET Values. Use the following formula to calculate the AAT3103-3 full scale LED current: ILED_FS = 1.2 · 4 · 48 RSET Constant Current Setting The LED full scale current is controlled by the RSET resistor. The following formula can be used to calculate the AAT3103-1/2/4 full scale LED current: For example, an 11.5kΩ 1% resistor is used to achieve 20mA full scale LED current operation. Device Switching Noise Performance The AAT3103 operates at a fixed frequency of approximately 0.9MHz 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 WLED backlight solutions. The AAT3103's softstart feature prevents noise transient effects associated with inrush currents during start-up of the charge pump circuit. ILED_FS = 1.2 · 4 · 60 RSET Table 4 shows the RSET resistor value for the AAT3103-1/2/4 for various LED full-scale current levels. For maximum accuracy, a 1% tolerance resistor is recommended. ILED_FS (mA) 30.2 20.1 15.1 10.0 RSET (kΩ) 9.53 14.3 19.1 28.7 Shutdown To activate the shutdown operation, the EN/SET input for the AAT3103-1/-2 should be pulsed low for longer than tOFF (500μs). For the 3103-4 PWM options, shutdown operation is enabled when the EN/PWM input is pulsed low longer than 500μs. In this state, the AAT3103 typically draws less than 1μA from the input. Registers are reset to 0 in shutdown. Table 4: Maximum LED Current and RSET Resistor Values (1% Resistor Tolerance) for the AAT3103. The S2C interface rising edges control the LED current from full scale to the LSB. For the AAT3103-1, 16 steps are employed. Figure 5 shows the LED current of the AAT3103-1 at different RSET values. 3103.2008.03.1.0 www.analogictech.com 11 PRODUCT DATASHEET AAT3103 ChargePumpTM 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 AAT3103, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the AAT3103 outputs are pure constant current sources and typically drive individual loads, it is difficult to measure the output voltage for a given output pin to derive an overall output power measurement. For any given application, WLED 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 WLED 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 WLED 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 AAT3103 efficiency may be quantified under very specific conditions and is dependent upon the input voltage versus the outputs of D1, D2 and D3 for a given constant current setting. Depending on the combination of VIN and voltages sensed at the current sources, the device will operate in load switch mode. When any one of the voltages sensed at the current sources 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. 3-Channel Charge-Pump LED Driver The ideal efficiency (η) in 1x charge-pump mode can be expressed as: POUT VF · ILED VF · ILED VF ≈ η= P = V ·I =V ·I VIN IN IN IN IN OUT -or- VF η (%) = V · 100 IN For a charge pump LED driver with VF of 3.2V and 4.2V input voltage, the theoretical efficiency is 76%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 73%. 2x Charge Pump Mode Efficiency The AAT3103 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 half of 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= 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 (η) can be rewritten as POUT VF · ILED VF · ILED VF η= P = V ·I =V ·2·I ≈2·V IN IN IN IN OUT IN -or- 1x Mode Efficiency The AAT3103 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. VF η (%) = 2 · V · 100 IN η= PF PIN For a charge pump LED current source driver with VF of 3.2V and 2.7V input voltage, the theoretical efficiency is 59%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 57%. Efficiency will decrease substantially as load current drops below 1mA or when the voltage level at VIN approaches the voltage level at VOUT. 12 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 ChargePumpTM Additional Applications The current sources of the AAT3103 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 as shown in Figure 6. For lower-cost applications, the flying capacitor can be removed. This will force the AAT3103 to operate in 1x mode. To maintain regulated LED current, the input supply voltage must be greater than the charge pump’s dropout voltage and the current source voltage drop in 1x mode. For example, to power 3.0V VF with 20mA LED current, VIN should be greater than 4.0V as shown in Figure 7. 3-Channel Charge-Pump LED Driver 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 three capacitors is a good starting point when choosing capacitors. Capacitor Characteristics Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3103. 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 to maximize charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage. 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 D1 C2 1μF C1 1μF 1 2 3 4 U1 AAT3103 D1 OUT CC+ IN D2 D3 10 9 8 AGND 7 RSET EN/SET 6 VIN C3 1μF 5 R1 14.3k EN/SET Figure 6: Higher Current, Single LED Application. U1 AAT3103 C2 1μF 1 2 3 4 D1 OUT CC+ IN D2 9 D3 AGND 8 7 10 D3 D2 D1 VIN C3 1μF 5 RSET 6 EN/SET R1 14.3k EN/SET Figure 7: Lower Cost 1x Mode Application. 3103.2008.03.1.0 www.analogictech.com 13 PRODUCT DATASHEET AAT3103 ChargePumpTM Evaluation Board Schematic DC+ 3-Channel Charge-Pump LED Driver DC+ C 10μF VCC 123 C2 1μF AAT3103-1 White LED Driver JP2 JP3 JP4 D3 D2 D1 JP1 C1 1μF 1 2 3 4 5 U1 AAT3103-1 D1 OUT CC+ IN D2 10 9 D3 8 AGND RSET 6 EN/SET JP5 R1 14.3k 7 C3 1μF R2 20k L1 4.7μH U4 AAT1217-3.3 S2Cwire Microcontroller 1 6 4 SW VIN SHDN VOUT FB GND 5 3 2 C6 4.7μF R8 10k C5 4.7μF R5 1k R4 1k R3 1k 1 2 3 4 U2 PIC12F675 VDD GP5 GP4 GP3 VSS GP0 GP1 GP2 8 7 6 5 C4 0.1μF VR1 POT10K R6 330Ω R7 330 Ω S1 UP S2 DOWN S3 CYCLE LED2 Red LED1 Green Figure 8: AAT3103 Evaluation Board Schematic. 14 www.analogictech.com 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Evaluation Board Layout 3-Channel Charge-Pump LED Driver Figure 9: AAT3103 Evaluation Board Component Side PCB Layout. Figure 10: AAT3103 Evaluation Board Solder Side PCB Layout. 3103.2008.03.1.0 www.analogictech.com 15 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM Ordering Information Package SC70JW-10 SC70JW-10 SC70JW-10 3-Channel Charge-Pump LED Driver Interface S Cwire S2Cwire PWM 2 Current Control, Inverting 16-step 8-step Linear Marking1 1DXYY 2TXYY Part Number (Tape and Reel)2 AAT3103IJQ-1-T1 AAT3103IJQ-2-T1 AAT3103IJQ-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 0.40 BSC 1.75 ± 0.10 0.225 ± 0.075 Top View 2.00 ± 0.20 0.15 ± 0.05 0.85 ± 0.15 2.20 ± 0.20 1.10 MAX 0.100 0.45 ± 0.10 2.10 ± 0.30 4° ± 4° 7° ± 3° Side View All dimensions in millimeters. End View 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 16 www.analogictech.com 0.05 ± 0.05 3103.2008.03.1.0 PRODUCT DATASHEET AAT3103 AAT3103 ChargePumpTM 3-Channel Charge-Pump LED Driver 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. 3103.2008.03.1.0 www.analogictech.com 17