AAT3142

AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications General Description The AAT3142 is a low noise, constant frequency charge pump DC/DC converter that uses a trimode load switch (1X), fractional (1.5X), and doubling (2X) conversion to maximize efficiency for white LED applications. The device produces current levels up to 30mA on each of its three current source outputs to drive various arrangements of LEDs from a 2.7V to 5.5V input. Outputs may be operated individually or in parallel for driving higher-current LEDs. A low external parts count (two 1µF flying capacitors and two small 1µF capacitors at VIN and CP) make the AAT3142 ideally suited for small battery-powered applications. AnalogicTech's Simple Serial Control™ (S2Cwire™) digital input is used to enable, disable, and set the LED drive current with a 32-level logarithmic scale LED brightness control. The AAT3142 has a thermal management system to protect the device in the event of a short-circuit condition at an output pin. Built-in soft-start circuitry prevents excessive inrush current during start-up. A high charge pump switching frequency enables the use of very small external capacitors. In shutdown mode, the device disconnects the load from VIN and reduces quiescent current to less than 1µA. The AAT3142 is available in the very small, Pb-free 12-pin TSOPJW package. Features • • • • • • • • • • • • • ChargePump™ VIN Range: 2.7V to 5.5V Tri-Mode 1X, 1.5X, and 2X Charge Pump for Maximum Efficiency and VF Coverage Drives Low-VF and High-VF Type LEDs Up to Three 30mA Outputs 32-Position Logarithmic Scale with Digital Control Low Noise Constant Frequency Operation 1MHz Switching Frequency Small Application Circuit Regulated Output Current Automatic Soft Start No Inductors IQ < 1µA in Shutdown 12-Pin TSOPJW Package Applications • • • • Color (RGB) Lighting Programmable Current Sources White LED Backlighting White Photo Flash for Digital Still Cameras Typical Application VIN C1+ C1 1μF CP VBATTERY C IN 1μF C CP 1μF C1C2+ C2 1μF AAT3142 C2D1 D2 D3 EN/SET EN/SET D3 GND D2 D1 3142.2007.03.1.2 1 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Pin Descriptions Pin # 1 2 3 4 5 6 7 8 9 10 11 12 Symbol C2+ CP C1C1+ D3 D2 GND D1 EN/SET IN GND C2- Function Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-. Charge pump output. Requires 1µF capacitor connected between this pin and ground. Flying capacitor 1 negative terminal. Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-. Current source output #3. Current source output #2. Ground pin; must be connected to Pin 11. Current source output #1. S2Cwire serial interface control pin. Input power supply. Requires 1µF capacitor connected between this pin and ground. Ground pin; must be connected to Pin 7. Flying capacitor 2 negative terminal. Pin Configuration TSOPJW-12 (Top View) C2+ CP C1C1+ D3 D2 1 2 3 4 5 6 12 11 10 9 8 7 C2GND IN EN/SET D1 GND 2 3142.2007.03.1.2 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Absolute Maximum Ratings1 Symbol VIN VEN/SET IOUT2 TJ Description Input Voltage EN/SET to GND Voltage Maximum DC Output Current Operating Junction Temperature Range Value -0.3 to 6 -0.3 to VIN + 0.3 150 -40 to 150 Units V V mA °C Thermal Information3 Symbol PD θJA Description Maximum Power Dissipation Thermal Resistance 4 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. Based on long-term current density limitation. 3. Mounted on an FR4 board. 4. Derate 6.25mW/°C above 25°C. 3142.2007.03.1.2 3 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Electrical Characteristics1 CIN = CCP = C1 = C2 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C, VIN = 3.5V. Symbol Description Conditions Min Typ Max Units 2.7 VD1:D3 = 2.0V, CP = 1X No Load Current, CP = 1.5X VIN = 3.5V, EN/SET = 0 VIN = 3.5V, TA = 25°C VD1:D3 = 3.6V, VIN = 3.5V VIN = 3.5V, IOUT(TOTAL) = 90mA, Measured from IN to CP 550 3 -10 -3 ±0.5 93 5.5 5 1 10 3 V µA mA µA % % % Input Power Supply VIN Operation Range Icc ISHDN IDX I(D-Match) ηCP Operating Current Shutdown Current Output Current Accuracy2 Current Matching3 Charge Pump Section Efficiency Charge Pump Section TSS Soft-Start Time FCLK Clock Frequency EN/SET VEN(L) Enable Threshold Low VEN(H) Enable Threshold High TEN/SET LO EN/SET Low Time TEN/SET HI MIN Minimum EN/SET High Time TEN/SET HI MAX Maximum EN/SET High Time TOFF EN/SET Off Timeout TLAT EN/SET Latch Timeout IEN/SET EN/SET Input Leakage 50 1 VIN = 2.7V VIN = 5.5V 0.4 1.4 0.3 50 75 500 500 1 75 µs MHz V V µs ns µs µs µs µA VEN/SET = 5.5V, VIN = 5.5V -1 1. The AAT3142 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. 2. Codes 2 through 7 are guaranteed to be within ±15% of stated current level. 3. Current matching is defined as I(D-Match) = (ID - IAVE)/IAVE. 4 3142.2007.03.1.2 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C, unless otherwise noted. Efficiency vs. Input Voltage (Code 26) 100 90 100 90 Efficiency vs. Input Voltage (D1 = 3.5V, D2 = 3.3V, D3 = 3.2V) Code 26 Efficiency (%) 80 70 60 50 40 30 2.9 3.0VF Efficiency (%) 80 70 60 50 40 30 2.9 3.5VF Code 28 Code 32 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 Input Voltage (V) Input Voltage (V) Efficiency vs. Input Voltage (D1-D2 = 3.5V, D3 = 3.2V) 100 90 Code 26 Efficiency (%) 80 70 60 50 40 Code 32 Code 28 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 30 2.9 Input Voltage (V) 3142.2007.03.1.2 5 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C, unless otherwise noted. Turn-On to 1X Mode (3x19mA Load) EN/SET (2V/div) VCP (4V/div) VDIODE (2V/div) IIN (100mA/div) EN/SET (2V/div) VCP (4V/div) VDIODE (2V/div) IIN (100mA/div) Turn-On to 1X Mode (3x30mA Load) Time (100µs/div) Time (100µs/div) Turn-On to 1.5X Mode (3x19mA Load) EN/SET (2V/div) VCP (4V/div) VDIODE (2V/div) IIN (100mA/div) EN/SET (2V/div) VCP (4V/div) VDIODE (2V/div) IIN (100mA/div) Turn-On to 1.5X Mode (3x30mA Load) Time (100µs/div) Time (100µs/div) Turn-Off from Full-Scale 2X Mode EN/SET (2V/div) VDIODE (2V/div) IIN (200mA/div) Time (200µs/div) 6 3142.2007.03.1.2 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C, unless otherwise noted. Charge Pump to Load Switch (1.5X Mode, 3x19mA Load) VIN (500mV/div) VCP (1V/div) VDIODE (500mV/div) IIN (50mA/div) Charge Pump to Load Switch (1.5X Mode, 3x30mA Load) VIN (500mV/div) VCP (1V/div) VDIODE (500mV/div) IIN (50mA/div) Time (5ms/div) Time (5ms/div) Charge Pump to Load Switch (2X Mode, 3x19mA Load) Charge Pump to Load Switch (2X Mode, 3x30mA Load) VIN (500mV/div) VCP (1V/div) VDIODE (500mV/div) IIN (50mA/div) VIN (500mV/div) VCP (1V/div) VDIODE (500mV/div) IIN (50mA/div) Time (5ms/div) Time (5ms/div) Load Switch to Charge Pump (1.5X Mode, 3x19mA Load) VIN (1V/div) VCP (4V/div) VDIODE (500mV/div) IIN (50mA/div) VIN (1V/div) VCP (4V/div) VDIODE (500mV/div) IIN (50mA/div) Load Switch to Charge Pump (1.5X Mode, 3x30mA Load) Time (2ms/div) Time (2ms/div) 3142.2007.03.1.2 7 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C, unless otherwise noted. Line Response (1X Mode, 3x19mA Load) Line Response (1X Mode, 3x30mA Load) VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div) Time (1ms/div) VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div) Time (1ms/div) Line Response (1.5X Mode, 3x19mA Load) VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div) Time (1ms/div) Line Response (1X Mode, 3x30mA Load) VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div) Time (1ms/div) Load Characteristics (1.5X Mode, 3x15mA Load) Load Characteristics (1.5X Mode, 3x30mA Load) VIN (20mV/div) IIN (10mA/div) VCP (20mV/div) VIN (20mV/div) IIN (10mA/div) VCP (20mV/div) Time (1µs/div) Time (1µs/div) 8 3142.2007.03.1.2 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C, unless otherwise noted. Input Current vs. Input Voltage (3x10mA) 70 60 50 200 Input Current vs. Input Voltage (3x30mA) 180 160 140 VDIODE = 3.4V VDIODE = 3.4V IIN (mA) 40 30 20 10 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 IIN (mA) 120 100 80 60 VDIODE = 3.0V 40 20 0 2.7 VDIODE = 3.0V 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) Diode Current vs. Input Voltage (30mA, 15mA Settings) 40 35 0.850 0.825 VIH and VIL vs. VIN VDIODE = 3.4V IDIODE (mA) 30 25 20 15 10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 0.800 0.775 0.750 0.725 0.700 VIH VIL VDIODE = 3.4V 0.675 0.650 0.625 0.600 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Input Voltage (V) 3142.2007.03.1.2 9 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Functional Block Diagram VIN Soft-Start Control 1MHz Oscillator Voltage Reference 1X 1.5X 2X Charge Pump C1+ C1C2+ C2- CP D/A D1 D2 D3 EN/SET S2Cwire Interface 32 x 8 bit ROM D/A D/A GND Functional Description The AAT3142 is a tri-mode load switch (1X) and high efficiency (1.5X or 2X) charge pump device intended for white LED backlight applications. To maximize power conversion efficiency, an internal sensing circuit monitors the voltage required on each constant current source output and sets the load switch and charge pump modes based on the input battery voltage and the current source output voltage. As the battery discharges over time, the AAT3142 charge pump is enabled when any of the three current source outputs nears dropout. The charge pump initially starts in 1.5X mode. If the charge pump output drops enough for any current source output to become close to dropout, the charge pump will automatically transition to 2X mode. Each of the three current source outputs is independently switched between the battery input (1X) or the charge pump output (1.5X or 2X), depending on the voltage at the current source output. Since the LED-to-LED forward voltage (VF) can vary as much as 1V, this function significantly enhances overall device efficiency when the battery input voltage level is greater than the voltage required at any current source output. The AAT3142 requires only four external components: two 1µF ceramic capacitors for the charge pump flying capacitors (C1 and C2), one 1µF ceramic input capacitor (CIN), and one 0.33µF to 1µF ceramic charge pump output capacitor (CCP). The three constant current outputs (D1 to D3) drive three individual LEDs with a maximum current of 30mA each. The EN/SET S2Cwire serial interface enables the AAT3142 and sets the current source magnitudes. 3142.2007.03.1.2 10 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Applications Information Constant Current Output Level Settings The constant current source amplitudes for D1 to D3 are set via the serial interface according to a logarithmic scale where each code is 1dB greater than the previous code. In this manner, LED brightness appears linear with each increasing code count. Because the outputs D1 to D3 are true independent constant current sources, the voltage observed on any single given output will be determined by the actual forward voltage (VF) for the LED being driven. Since the output current of the AAT3142 is programmable, no PWM (pulse width modulation) or additional control circuitry are 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 output current of the AAT3142 can be changed successively to brighten or dim LEDs in smooth transitions (e.g., to fade out) or in abrupt steps, giving the user complete programmability and real-time control of LED brightness. The individual current level settings are each approximately 1dB apart for settings above Code 8 (see Figure 1). The current level settings below Code 8 are more than 1dB apart and serve the needs of transmissive displays and other low-current applications. 1.00 Current (mA) 0.10 0.01 0.00 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 Code Figure 1: Normalized Current Level Settings. Code 1 2 3 4 5 6 7 8 IOUT (typ) (mA) 0.0 0.1 0.2 0.4 0.5 0.7 1.1 1.8 Code 9 10 11 12 13 14 15 16 IOUT (typ) (mA) 2.0 2.2 2.5 2.8 3.2 3.5 4.0 4.5 Code 17 18 19 20 21 22 23 24 IOUT (typ) (mA) 5.1 5.6 6 7 8 9 10 12 Code 25 26 27 28 29 30 31 32 IOUT (typ) (mA) 13 15 17 19 21 24 27 30 Figure 1: Constant Current Source Output Nominal Programming Levels. 3142.2007.03.1.2 11 AAT3142 High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications S2Cwire Serial Interface The current source output magnitude is controlled by the EN/SET pin, using AnalogicTech's S2Cwire interface. The interface records rising edges of the EN/SET pin and decodes them into 32 individual current level settings with Code 1 reserved for no current. Once EN/SET has been held in the logic high state for time TLAT, the programmed current is seen at the current source outputs, and the internal data register is reset to 0. For subsequent current level programming, the number of rising edges corresponding to the desired code must be entered on the EN/SET pin. When EN/SET is held low for an amount of time greater than TOFF, the AAT3142 enters into shutdown mode and draws less than 1µA from VIN. The internal data register is reset to 0 during shutdown. S2Cwire Serial Interface Timing THI TLO TLAT TOFF EN/SET 1 2 n-1 n