AAT2801IXN-4.5-T1

Multi-Mode Charge Pump for White LED Backlight and Flash Applications General Description The AAT2801 is a member of AnalogicTech's Total Power Management IC™ (TPMIC™) product family. It has a dual charge pump architecture designed to support both the white LED backlight and flash applications for systems operating with Lithium-Ion batteries. The backlight charge pump provides power required to drive up to four LEDs. To maximize power efficiency, it automatically selects 1X, 1.5X, or 2X mode. The device produces current levels up to 30mA on each of its four current source outputs. AnalogicTech's Simple Serial Control™ (S2Cwire™) interface is used to enable, disable, and set the LED drive current with a 32-level logarithmic scale LED brightness control. The flash charge pump is a charge pump doubler with a regulated output voltage. It is designed to deliver 120mA of continuous current and up to 250mA of pulsed current. It has an independent enable pin for improved power savings. The AAT2801 is equipped with AnalogicTech’s AutoBias™ technology which allows individual LEDs to be powered either by charge pump or battery input, determined internally and automatically to maximize the power efficiency even with a large difference in LED forward voltage. The AAT2801 has thermal protection and built-in soft-start circuitry. A high charge pump switching frequency enables the use of very small external capacitors. The AAT2801 is available in the 16-pin TDFN44 package. AAT2801 Features • • • • • • • • • • • • • • ChargePump™ VIN Range: 2.7V to 5.5V Dual Charge Pump — Flash: Charge Pump Doubler — Backlight: Tri-Mode Charge Pump Drives Low-VF and High-VF LEDs Up to Four 30mA Outputs 32-Position Logarithmic Scale with Digital Control Low Noise Constant Frequency Operation 1MHz Switching Frequency AutoBias Technology Regulated 4.5/5.0 Volts VOUT_FLASH Up to 250mA of Current for Flash Automatic Soft Start No Inductors IQ 1.4V VEN/SET > 1.4V VEN/SET < 0.6V VEN/SET > 1.4V VEN/SET/EN_FLSH = 5V, VIN = 5V 1. The AAT2801 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 2801.2006.04.1.3 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–White LED Backlight Driver Section VIN = 3.5V, CIN = 2.2µF, CCP = C1 = C2 = 1.0µF; TA = 25°C, unless otherwise noted. AAT2801 Efficiency vs. VIN (Code 26) 100 90 100 90 Efficiency vs. VIN (D1 = 3.5V; D2 = 3.3V; D3 = 3.2V; D4 = 3.0V) Efficiency (%) Efficiency (%) 80 70 60 50 40 30 2.9 3.0 3.1 3.0VF 80 70 60 50 40 30 Code 26 3.5VF Code 28 2.9 3.0 3.1 3.2 Code 32 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 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. VIN (D1-D2 = 3.5V; D3-D4 = 3.2V) 100 90 5.0 Operating Current (Code 23; EN_FLSH Off) Code 26 Efficiency (%) 80 4.0 3.0 2.0 1.0 V_DX = 3.3V 60 50 40 30 2.9 Code 28 3.0 3.1 3.2 Code 32 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 IIN (A) 70 V_DX = 3.0V 0.0 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) Input Voltage (V) Operating Current (Code 23; EN_FLSH On; IOUT = 100mA) 8.0 7.0 6.0 V_DX = 3.3V IIN (A) 5.0 4.0 3.0 2.0 1.0 0.0 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 V_DX = 3.0V Input Voltage (V) 2801.2006.04.1.3 5 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–White LED Backlight Driver Section VIN = 3.5V, CIN = 2.2µF, CCP = C1 = C2 = 1.0µF; TA = 25°C, unless otherwise noted. AAT2801 Turn-On to 1X Mode (4x19mA 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 (4x30mA Load) Time (100µs/div) Time (100µs/div) Turn-On to 1.5X Mode (4x19mA Load) EN/SET (2V/div) VCP (4V/div) VDIODE (2V/div) IIN (100mA/div) Turn-Off from Full-Scale 2X Mode EN/SET (2V/div) VDIODE (2V/div) IIN (200mA/div) Time (100µs/div) Time (100µs/div) Flash Section Turn-On (VIN = 3.5V; IOUT = 100mA; EN/SET = GND) Flash Section Turn-On (VIN = 3.5V; IOUT = 200mA; EN/SET = GND) EN_FLSH (2V/div) VOUT (2V/div) IIN (100mA/div) EN_FLSH (2V/div) VOUT (2V/div) IIN (100mA/div) Time (100µs/div) Time (100µs/div) 6 2801.2006.04.1.3 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–White LED Backlight Driver Section VIN = 3.5V, CIN = 2.2µF, CCP = C1 = C2 = 1.0µF; TA = 25°C, unless otherwise noted. AAT2801 Charge Pump to Load Switch (1.5X Mode; 4x19mA Load) VIN (500mV/div) VCP (1V/div) VDIODE (500mV/div) IIN (50mA/div) Charge Pump to Load Switch (1.5X Mode; 4x30mA 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; 4x19mA Load) Charge Pump to Load Switch (2X Mode; 4x30mA 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; 4x19mA 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; 4x30mA Load) Time (2ms/div) Time (2ms/div) 2801.2006.04.1.3 7 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–White LED Backlight Driver Section VIN = 3.5V, CIN = 2.2µF, CCP = C1 = C2 = 1.0µF; TA = 25°C, unless otherwise noted. AAT2801 Line Response (1X Mode; 4x19mA Load) Line Response (1X Mode; 4x30mA 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; 4x19mA Load) VIN (0.5V/div) VDX (20mV/div) VCP (0.5V/div) IDX (10mA/div) Time (1ms/div) Line Response (1.5X Mode; 4x30mA Load) VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div) Time (1ms/div) Line Response (IOUT = 100mA; I_DX = 4x19mA; 1.5X Mode) VIN (0.5V/div) VCP (0.5V/div) VDX (20mV/div) IDX (10mA/div) VF (10mV/div) Time (1ms/div) 8 2801.2006.04.1.3 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–White LED Backlight Driver Section VIN = 3.5V, CIN = 2.2µF, CCP = C1 = C2 = 1.0µF; TA = 25°C, unless otherwise noted. AAT2801 Operating Characteristics (I_DX = 4x15mA; 1.5X Mode) VIN = 3.0V VDX (20mV/div) IIN (10mA/div) VCP (20mV/div) VF (40mV/div) Operating Characteristics (I_DX = 4x15mA; 1.5X Mode; IOUT = 100mA) VIN = 3.0V VDX (20mV/div) IIN (10mA/div) VCP (20mV/div) Time (1µs/div) Time (1µs/div) Operating Characteristics (I_DX = 4x30mA; 1.5X Mode) VIN = 3.5V VDX (20mV/div) IIN (10mA/div) VCP (40mV/div) VDX (20mV/div) IIN (10mA/div) VCP (40mV/div) VF (40mV/div) Time (1µs/div) Operating Characteristics (I_DX = 4x30mA; 1.5X Mode; IOUT = 100mA) Time (1µs/div) Input Current vs. Input Voltage (4x10mA) 90 80 70 60 300 Input Current vs. Input Voltage (4x30mA) VDIODE = 3.4V 250 200 VDIODE = 3.4V IIN (mA) 50 40 30 20 10 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 IIN (mA) VDIODE = 3.0V 150 100 50 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) 2801.2006.04.1.3 9 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–White LED Backlight Driver Section VIN = 3.5V, CIN = 2.2µF, CCP = C1 = C2 = 1.0µF; TA = 25°C, unless otherwise noted. AAT2801 Diode Current vs. Input Voltage (30mA; 15mA settings) 40 35 0.850 0.825 VIH and VIL vs. VIN VDIODE = 3.4V 0.800 0.775 0.750 0.725 0.700 0.675 0.650 0.625 0.600 IDIODE (mA) 30 25 20 15 10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 VIH VIL VDIODE = 3.4V 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Input Voltage (V) 10 2801.2006.04.1.3 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–Flash Driver Charge Pump Section VIN = 3.5V, CIN = 2.2µF, C3 = CF = 1.0µF, TA = 25°C, unless otherwise noted. AAT2801 Output Voltage vs. Output Current 5.0 4.8 4.6 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 0 40 80 120 160 200 Efficiency vs. Supply Voltage 100 90 80 50mA Output Voltage (V) VIN=3.3 VIN=3.6 Efficiency (%) 70 60 50 40 30 20 10 0 2.7 3.0 3.3 3.6 3.9 4.2 4.5 100mA 150mA VIN = 2.7 VIN = 3.0 Output Current (mA) Supply Voltage (V) Efficiency vs. Load Current Maximum Current Pulse (mA) 100 90 80 VIN = 2.7V VIN = 3.0V Maximum Current Pulse vs. Supply Voltage 600 500 400 300 200 100 0 3.0 3.2 3.4 3.6 3.8 4.0 4.2 One-shot pulse duration = 250ms VOUT> 4.0V Efficiency (%) 70 60 50 40 30 20 10 0 0.1 1.0 10 100 1000 VIN = 3.3V VIN = 3.6V Load Current (mA) Supply Voltage (V) Load Response (100mA Load) VIN = 3.5V VOUT (10mV/div) VOUT (10mV/div) VIN = 3.5V Load Response (50mA Load) IOUT (50mA/div) IOUT (20mA/div) Time (5ms/div) Time (5ms/div) 2801.2006.04.1.3 11 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Typical Characteristics–Flash Driver Charge Pump Section VIN = 3.5V, CIN = 2.2µF, C3 = CF = 1.0µF, TA = 25°C, unless otherwise noted. AAT2801 Startup 1.00 0.95 VEN Threshold vs. Supply Voltage VEN Threshold (V) ENABLE (1V/div) 0.90 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 2.7 3.1 ILOAD = 150mA @ VIN = 3.3V ILOAD = 100mA @ VIN = 3.0V VIH VIL VOUT (1V/div) ILOAD = 150mA @ VIN = 3.3V 3.5 3.9 4.3 4.7 5.1 5.5 Time (100µs/div) Supply Voltage (V) Normalized Output Voltage vs. Temperature Normalized Output Voltage (%) 2.0 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0 -50 -30 -10 10 30 50 70 90 IOUT = 25mA Temperature (°C) 12 2801.2006.04.1.3 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Functional Block Diagram C3 + C3 - AAT2801 2X CP Soft Start OUT_FLSH EN_FLSH 1MHz Oscillator IN VREF Soft-Start Control 1MHz Oscillator Voltage Reference C1+ 1X 1.5X 2X Charge Pump C1C2+ C2CP D1 D2 D3 D4 D/A EN/SET Control Logic D/A D/A D/A GND Functional Description The AAT2801 is a dual charge pump for white LED and flash applications. The charge pump for white LED application 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 AAT2801 charge pump is enabled when any of the four current source outputs nears dropout. The charge pump initially 2801.2006.04.1.3 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. The second section of the AAT2801 contains a voltage doubling charge pump to supply flash LED functions. The voltage doubling charge pump provides a 4.5V regulated output and has an independent enable control. AutoBias Technology Each of the four current source outputs for the white LED backlight charge pump section is independently switched between the battery input (1X) or the charge pump output (1.5X or 2X), depending 13 Multi-Mode Charge Pump for White LED Backlight and Flash Applications on the voltage at the current source output. Since the LED to LED VF can vary as much as 1 volt, this function significantly enhances overall efficiency of the white LED backlight charge pump section when the battery input voltage level is greater than the voltage required at any current source output. AAT2801 Applications Information— White LED Backlight Section Constant Current Output Level Settings The constant current source amplitudes for D1 to D4 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 D4 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 AAT2801 is programmable, no PWM (pulse width modulation) 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 output current of the AAT2801 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 32 individual current level settings are each approximately 1dB apart (see Current Level Settings below). Code 32 is full scale; Code 2 is full scale attenuated by 31dB; and Code 1 is reserved as a "no current" setting. Flash Driver For flash applications, the voltage doubling charge pump section is used to support the high current demand required by the application. Charge pump regulation is achieved by sensing the output voltage through an internal resistor divider network. The free running charge pump switching frequency is approximately 1MHz. The charge pump is designed to deliver up to 120mA of continuous current and 250mA of pulsed current for up to 500ms. The AAT2801 requires only six external components: three 1µF ceramic capacitors for the charge pump flying capacitors (C1, C2 and C3), one 1µF ceramic input capacitor (CIN), one 1µF ceramic charge pump output capacitor (CCP), and one 1µF for the flash output (CF). The four constant current outputs (D1 to D4) drive four individual LEDs with a maximum current of 30mA each. The EN/SET S2Cwire serial interface enables the AAT2801 and sets the current source magnitudes. A separate flash enable pin (EN_FLSH) is provided to independently control the flash charge pump circuit. Normalized Current Level Settings 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 14 2801.2006.04.1.3 Multi-Mode Charge Pump for White LED Backlight and Flash Applications Constant Current Source Output Nominal Programming Levels (mA) Code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 AAT2801 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 each 1dB apart 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 AAT2801 enters into shutdown mode and draws less than 1µA from VIN. The internal data register is reset to 0 during shutdown. IOUT (typ) (mA) 0.0 0.1 0.2 0.4 0.5 0.7 1.1 1.8 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 25 26 27 28 29 30 31 32 IOUT (typ) (mA) 5.1 5.6 6.4 7.2 8.1 9.2 10.2 11.5 13.1 14.7 16.6 18.6 20.9 23.6 26.6 30.0 S2Cwire Serial Interface Timing Diagram THI TLO TLAT TOFF EN/SET 1 2 n-1 n