AAT2806

Dual High Efficiency Charge Pump for White LED and Flash Applications General Description The AAT2806 is a dual charge pump designed to support both the white LED backlight and flash applications for systems operating with lithium-ion/polymer batteries. The backlight charge pump is capable of driving up to four LEDs at a total of 80mA. The current sinks may be operated individually or in parallel for driving higher current LEDs. To maximize power efficiency, the charge pump operates in 1X, 1.5X, or 2X mode, where the mode of operation is automatically selected by comparing the forward voltage of each LED with the input voltage. AnalogicTech's S2Cwire™ (Simple Serial Control™) serial digital input is used to enable, disable, and set current for each LED with an eight-level logarithmic scale plus four low-current settings down to 50µA for optimized efficiency, with a typical operating quiescent current of less than 50µA. 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 AAT2806 has thermal protection and built-in soft-start circuitry. A low-current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1µA. The AAT2806 is available in a Pb-free, space-saving, thermally-enhanced TDFN44-16 package and is rated over the -40°C to +85°C temperature range. AAT2806 Features • • • ChargePump™ • • • • • • VIN Range: 2.7V to 5.5V Dual Charge Pump to Support Backlight and Flash LEDs Backlight Charge Pump: — Regulated Current — Four Current Sink Inputs — S2Cwire Brightness Control — Tri-Mode Charge Pump — Maximum 20mA of Current Per Input — Low IQ (50µA) in Light Load Mode Flash Charge Pump: — Regulated Output Voltage — Up to 250mA of Pulsed Current Independent Backlight/Flash Control Low Noise 1MHz Constant Frequency Operation Automatic Soft Start No Inductors Available in TDFN44-16 Package Applications • • • Color (RGB) Lighting White LED Backlighting White LED Photo Flash Typical Application C1 1μF C2 1μF C3 1μF C1+ C1- C2+ C2- C3+ C3VOUT_FL VIN VIN CIN 1 μF COUT 1μF VOUT_FLASH Flash AAT2806 VOUT_BL Backlight D1 EN/SET EN_FLSH EN/SET EN_FLSH GND D1 D2 D3 D4 D2 D3 D4 COUT 1μF 2806.2006.04.1.8 1 Dual High Efficiency Charge Pump for White LED and Flash Applications Pin Descriptions Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 EP AAT2806 Symbol C3C3+ VOUT_FL VIN D4 D3 D2 D1 GND EN/SET C1+ C1VOUT_BL C2+ C2EN_FLSH Function Flying capacitor 3 negative terminal. Flying capacitor 3 positive terminal. Connect a 1µF capacitor between C3+ and C3-. Regulated output voltage for the flash LED. Requires 1µF capacitor connected between this pin and ground. Input power supply. Requires 1µF capacitor connected between this pin and ground. Current sink input 4. Current sink input 3. Current sink input 2. Current sink input 1. Ground. S2Cwire serial interface control pin. It is used to enable/disable the backlight charge pump and to control the brightness of the white LEDs. Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-. Flying capacitor 1 negative terminal. Regulated output voltage for the white LEDs. Requires 1µF capacitor connected between this pin and ground. Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-. Flying capacitor 2 negative terminal. Enable/disable pin for the flash charge pump. Exposed paddle (bottom); connect to GND directly beneath package. Pin Configuration TDFN44-16 (Top View) C3C3+ VOUT_FL VIN D4 D3 D2 D1 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 EN_FLSH C2C2+ VOUT_BL C1C1+ EN/SET GND 2 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications Absolute Maximum Ratings1 Symbol VIN VEN/SET; EN_FL TLEAD AAT2806 Description Input Voltage EN/SET; EN_FL to GND Voltage Maximum Soldering Temperature (at leads, 10 sec) Value -0.3 to 6.0 -0.3 to VIN + 0.3 300 Units V V °C Thermal Information2 Symbol PD θJA Description Maximum Power Dissipation Maximum Thermal Resistance 3 Value 2.0 50 Units W °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 board. 3. Derate 6.25mW/°C above 25°C. 2806.2006.04.1.8 3 Dual High Efficiency Charge Pump for White LED and Flash Applications Electrical Characteristics1 VIN = 3.6V; CIN = COUT = C1 = C2 = C3 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol VIN AAT2806 Description Operation Range Conditions Min Typ Max Units 5.5 1 3.0 3.7 µA 4.5 1.0 10 mA µA % % Ω 4.68 4.7 V V Input Power Supply ICC ISHDN IDX I(D-Match) RSINK VOUT_FL IOUT_FL TSS FCLK VEN(L) VEN(H) TEN/SET LO TEN/SET_HI_MIN TEN/SET_HI_MAX TOFF TLAT II 2.7 1X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load 0.3 Current; EN_FLSH = GND, EN/SET = VIN 1.5X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load 1.0 Current; EN_FLSH = GND, EN/SET = VIN 2X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load 2.0 Operating Current Current; EN_FLSH = GND, EN/SET = VIN EN_FLSH = GND, 50µA Output Setting, 50 1X Mode 3.0 ≤ VIN ≤ 5.5, No Load Current; 2.0 EN_FLSH = VIN, EN/SET = GND Shutdown Current EN_FLSH = EN/SET = 0 2, 3 Input Current Accuracy ISET = 20mA and ISET = 4.1mA; TA = 25°C -10 Current Matching Between Any VD1:D4 = 3.6V, VIN = 3.5V 0.5 Two Current Sink Inputs2, 4 Sink Switch Impedance (each)2 7 3.0V < VIN < 5V, IOUT = 100mA; 4.32 4.5 Flash Charge Pump Output EN_FLSH = VIN 5 3.0V < VIN < 5V, IOUT = 150mA; 4.3 4.5 Voltage EN_FLSH = VIN Maximum Continuous IOUT5 VIN = 3.6V; VOUT = 4.5V; EN_FLSH = VIN 120 Maximum Pulsed IOUT5 VIN = 3.6V; VOUT = 4.5V; IPULSED < 500ms 250 Soft-Start Time 100 Clock Frequency 1.0 Enable Threshold Low Enable Threshold High 1.4 EN/SET Low Time 0.3 Minimum EN/SET High Time 50 Maximum EN/SET High Time EN/SET Off Timeout EN/SET Latch Timeout Enable and EN/SET Input -1.0 Leakage mA mA µs MHz V V µs ns µs µs µs µA 0.4 75 75 500 500 1.0 1. The AAT2806 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. Specification applies only to the tri-mode charge pump. 3. Determined by the average of all active channels. 4. Current matching is defined as the deviation of any sink current from the average of all active channels. 5. Specification applies only to the charge pump doubler. 4 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics– Flash Driver Charge Pump Section Output Voltage vs. Output Current (VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND) 4.60 AAT2806 Maximum Current Pulse vs. Supply Voltage (VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND) Maximum Current Pulse (mA) 450 400 350 300 250 200 150 100 50 Output Voltage (V) 4.56 4.52 4.48 4.44 One-shot pulse duration = 250ms VOUT > 4.0V 3.6V 3.0V 2.7V 3.3V 4.40 0.1 1.0 10.0 100.0 1000.0 0 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 Output Current (mA) Supply Voltage (V) Start-Up Time (50mA Load) Start-Up Time (100mA Load) EN_FLSH (1V/div) EN_FLSH (1V/div) VOUT_FL (1V/div) VOUT_FL (1V/div) Time (100µs/div) Time (100µs/div) Load Response vs. Time (50mA Load) VIN = 3.5V VOUT_FL (10mV/div) VOUT_FL (10mV/div) Load Response vs. Time (100mA Load) VIN = 3.5V IOUT (20mA/div) IOUT (50mA/div) Time (5ms/div) Time (5ms/div) 2806.2006.04.1.8 5 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics– Flash Driver Charge Pump Section Output Ripple Voltage vs. Time (IOUT = 50mA @ VIN = 3.5V) VIN (10mV/div) VOUT (10mV/div) VIN (10mV/div) VOUT (20mV/div) AAT2806 Output Ripple Voltage vs. Time (IOUT = 100mA @ VIN = 3.5V) IIN (10mA/div) IIN (10mA/div) Time (500ns/div) Time (500ns/div) Supply Current vs. Supply Voltage IOUT = 0μA C3 = 1μF VEN_FL = VIN Oscillator Frequency vs. Supply Voltage Oscillator Frequency (MHz) 1.30 3.00 Supply Current (mA) 2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 2.5 1.25 +25°C 1.20 +85°C -40°C 1.15 3.0 3.5 4.0 4.5 5.0 1.10 2.7 3.2 3.7 4.2 4.7 Supply Voltage (V) Supply Voltage (V) 6 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics– White LED Backlight Driver Section Turn-On to 1X Mode (VIN = 4.2V; 20mA Load) AAT2806 Turn-On to 1.5X Mode (VIN = 3.5V; 20mA Load) EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) Time (100µs/div) EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) Time (100µs/div) Turn-On to 2X Mode (VIN = 2.8V; 20mA Load) EN (2V/div) VF (1V/div) Turn-Off from 1.5X Mode (VIN = 3.5V; 20mA Load) EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) IIN (100mA/div) Time (100µs/div) Time (500µs/div) Efficiency vs. Supply Voltage 100 90 10mA VF = 3.1V 20mA VF = 3.4V 20.4 20.2 Current Matching vs. Temperature Channel 2 Channel 4 Channel 3 Channel 1 Efficiency (%) 80 70 60 50 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 Current (mA) 20.0 19.8 19.6 19.4 19.2 19.0 -40 -20 0 20 40 60 80 Supply Voltage (V) Temperature (°C) 2806.2006.04.1.8 7 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics– White LED Backlight Driver Section Load Characteristics (VIN = 3.7V; 1.5X Mode; 14mA Load) AAT2806 Load Characteristics (VIN = 2.7V; 2X Mode; 14mA Load) VIN (40mV/div) CP (40mV/div) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) VSINK (40mV/div) Time (500ns/div) Time (500ns/div) Load Characteristics (VIN = 3.9V; 1.5X Mode; 20mA Load) Load Characteristics (VIN = 2.9V; 2X Mode; 20mA Load) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) VIN (40mV/div) CP (40mV/div) VSINK (40mV/div) Time (500ns/div) Time (500ns/div) EN/SET Latch Timeout vs. Input Voltage EN/SET Latch Timeout (μs) 350 400 EN/SET Off Timeout vs. Input Voltage EN/SET Off Timeout (μs) 300 250 200 150 100 50 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 5.5 350 300 250 200 150 100 50 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 -40°C -40°C 25°C 85°C 25°C 85°C Input Voltage (V) Input Voltage (V) 8 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics– White LED Backlight Driver Section Input Ripple vs. Input Voltage Enable Threshold High (V) 18 16 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 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 AAT2806 Enable Threshold High vs. Input Voltage Amplitude (mV) 14 12 10 8 6 4 2 0 2.50 2.67 2.84 3.01 3.18 3.35 3.52 3.69 3.86 4.03 4.20 -40°C 20mA 25°C 85°C 10mA Input Voltage (V) Input Voltage (V) Enable Threshold Low vs. Input Voltage Enable Threshold Low (V) 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 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 -40°C 25°C 85°C Input Voltage (V) 2806.2006.04.1.8 9 Dual High Efficiency Charge Pump for White LED and Flash Applications Functional Block Diagram C3+ Soft-Start AAT2806 C3- EN_FLSH 1MHz Oscillator 2X Charge Pump VOUT_FLSH VIN VREF Soft-Start Control 1MHz Oscillator Voltage Reference D/A 6 x 16 Bit ROM D/A D/A 1X 1.5X 2X Charge Pump C1+ C1C2+ C2VOUT_BL D1 D2 D3 D4 GND EN/SET Control Logic 6 x 16 Bit ROM D/A Functional Description The AAT2806 is a dual charge pump designed for flash and white LED applications. The backlight charge pump is a tri-mode load switch (1X) and high efficiency (1.5X or 2X) charge pump device. To maximize power conversion efficiency, an internal sensing circuit monitors the voltage required on each constant current sink input and sets the load switch and charge pump modes based on the input battery voltage and the current sink input voltage. As the battery voltage discharges over time, the white LED charge pump is enabled when any of the four current sink inputs near 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. The four constant current sink inputs D1 to D4 can drive four individual LEDs with a maximum current of 20mA per LED. The unused sink inputs must be connected to VOUT_BL; otherwise, the part will operate only in 2X charge pump mode. The S2Cwire serial interface enables and sets the constant current sink magnitudes. S2Cwire addressing allows the LED main channels D1 to D3 to be controlled independently from the LED sub-channel D4. 10 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications The flash charge pump is a charge pump doubler with regulated output voltage. It is designed to deliver 120mA of continuous current and 250mA of pulsed current. The AAT2806 requires six external components: three 1µF ceramic capacitors for the charge pump flying capacitors (C1, C2, and C3), one 1µF ceramic input capacitor (CIN), one 0.33µF to 1µF ceramic capacitor for the backlight charge pump output capacitor (COUT), and one 1µF ceramic capacitor for the flash charge pump output capacitor (COUT). IOUT (mA) D1-D3 Sub-Group D4 20 14 10 7 20 14 10 7 0 0 0 0 0.05 0.5 1 2 20 14 10 7 0 0 0 0 20 14 10 7 0.05 0.5 1 2 AAT2806 Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Constant Current Output Level Settings The constant current level for the LED channels is set via the S2Cwire serial interface (see Table 1). Because the inputs D1 to D4 are true independent constant current sinks, the voltage observed on any single given input will be determined by the difference between VOUT and the actual forward voltage (VF) of the LED being driven. Since the constant current levels are 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 LED current drive 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 realtime control of LED brightness. The AAT2806 offers an additional Low Current mode with reduced quiescent current (Data 13 to 16). This mode is especially useful for low-current applications where a continuous, low-current state is maintained. The reduction in quiescent current significantly reduces the impact due to maintaining a continuous backlighting state. Table 1: Constant Current Programming Levels. S2Cwire Serial Interface The current sink input magnitude on the backlight charge pump is controlled by AnalogicTech's S2Cwire serial digital input. The interface relies on the number of rising edges of the EN/SET pin to address and load the registers. S2Cwire latches data or address after the EN/SET pin has been held high for time TLAT. The interface records rising edges of the EN/SET pin and decodes them into 16 different states, as indicated in Table 1. There are four brightness levels for the main or sub-display group with the possibility of individually turning ON or OFF each group. To further optimize power efficiency, the device also offers four low-current levels for dim LED operation (Data 13 to 16). During this low-current mode, the internal supply current reduces to only 50µA typical. The counter can be clocked at speeds up to 1MHz, such that intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to 20mA. Once the final clock cycle is input for the desired brightness level, the EN/SET pin is held high to maintain the device output current at the programmed level. The device is disabled 500µs (TOFF) after the EN/SET pin transitions to a logic low state. 2806.2006.04.1.8 11 Dual High Efficiency Charge Pump for White LED and Flash Applications S2Cwire Serial Interface Timing Diagram T HI TLO TLAT TOFF AAT2806 EN/SET 1 2 n-1 n ≤ 16 Data Reg 0 n 0 Disabled Current Sinks The backlight charge pump is equipped with an auto-disable feature to protect against an LED failure condition. Current sink inputs that are not used should be disabled. To disable and properly terminate unused current sink inputs, they must be tied to VOUT. If left unconnected or terminated to ground, the part will be forced to operate in 2X charge pump mode. Properly terminating unused current sink inputs is important to prevent the charge pump modes from activating prematurely. When properly terminated, only a small sense current flows for each disabled channel. The sense current for each disabled channel is less than 10µA. In some instances (e.g., in high-luminous-output applications such as photo-flash), it may be necessary to drive high-VF type LEDs. The low-dropout current-sinks in the AAT2806 make it capable of driving LEDs with forward voltages as high as 4.3V at full current from an input supply as low as 3.0V. Outputs can be paralleled to drive high-current LEDs without complication. Device Switching Noise Performance The AAT2806 operates at a fixed frequency of approximately 1MHz to control noise and limit harmonics that can interfere with the RF operation of cellular telephone handsets or other 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 AAT2806 soft-start feature prevents noise transient effects associated with inrush currents during startup of the charge pump circuit. Applications Information LED Selection The AAT2806 is specifically intended for driving white LEDs. However, the device design will allow the AAT2806 to drive most types of LEDs with forward voltage specifications ranging from 2.0V to 4.3V. LED applications may include main display backlighting, camera photo-flash applications, color (RGB) LEDs, infrared (IR) diodes for remotes, and other loads benefiting from a controlled output current generated from a varying input voltage. Since the D1 to D4 input current sinks are matched with negligible voltage dependence, the LED brightness will be matched regardless of the specific LED forward voltage (VF) levels. Capacitor Selection Careful selection of the six external capacitors CIN, C1, C2, C3, and COUT (for backlight and flash) 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 six capacitors is a good starting point when choosing capacitors. 12 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications Capacitor Characteristics Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT2806. 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 maximize charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage. AAT2806 Charge Pump Power Efficiency Backlight Charge Pump: The charge pump efficiency discussion in the following sections only accounts for the efficiency of the charge pump section itself. Due to the unique circuit architecture, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the outputs are pure constant current sinks and typically drive individual loads, it is difficult to measure the output voltage for a given output (D1 to D4) 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 components count, reliability, operating range, and total energy usage...not just "% efficiency." Efficiency of the AAT2806 may be quantified under very specific conditions and is dependent upon the input voltage versus the output voltage seen across the loads applied to outputs D1 through D4 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 1.5X or 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. Load Switch Mode Efficiency: The load switch mode is operational at all times and functions alone to enhance device power conversion efficiency when VIN is greater than the voltage across the load. When in load switch mode, the voltage conversion efficiency is defined as output power divided by input power: 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. 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., greater than 2.2µF) are often available in lowcost Y5V and Z5U dielectrics, but capacitors greater than 1µF are not typically required for AAT2806 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. Thermal Protection The AAT2806 has a thermal protection circuit that will shut down the two charge pumps if the die temperature rises above the thermal limit. η= POUT PIN 2806.2006.04.1.8 13 Dual High Efficiency Charge Pump for White LED and Flash Applications The expression to define the ideal efficiency (η) can be rewritten as: POUT VOUT × IOUT VOUT = = PIN VIN × IOUT VIN AAT2806 η= -or⎛ VOUT ⎞ ⎝ VIN ⎠ For a charge pump with an output of 5V and a nominal input of 3.5V, the theoretical efficiency is 95%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 93%. These figures are in close agreement for output load conditions from 1mA to 100mA. Efficiency will decrease as load current drops below 0.05mA or when the level of VIN approaches VOUT. Flash Charge Pump: The flash charge pump is a regulated output voltage doubling charge pump. The efficiency is defined as a linear voltage regulator with an effective output voltage that is equal to two times the input voltage. The expression to define the ideal efficiency can be written as: POUT VOUT × IOUT VOUT = = PIN VIN × 2.0IOUT 2.0VIN η(%) = 100 Charge Pump Mode Efficiency: Fractional charge pumps will boost the input supply voltage in the event where VIN is less than the voltage required on the constant current source outputs. The efficiency (η) can be simply defined as a linear voltage regulator with an effective output voltage that is equal to one and a half or two times the input voltage. Efficiency (η) for an ideal 1.5X charge pump can typically be expressed as the output power divided by the input power: η= -or⎛ VOUT ⎞ ⎝ 2.0VIN⎠ η= POUT PIN η(%) = 100 In addition, with an ideal 1.5X charge pump, the output current may be expressed as 2/3 of the input current. The expression to define the ideal efficiency (η) can be rewritten as: VOUT × IOUT VOUT POUT = = PIN VIN × 1.5IOUT 1.5VIN η= For a charge pump with an output of 5V and a nominal input of 3V, the theoretical efficiency is 83.3%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at approximately 82%. Efficiency will decrease as the level of VIN approaches that of the regulated VOUT. Refer to the device typical characteristics curves for expected actual efficiency based on either input voltage or load current. -or⎛ VOUT ⎞ ⎝ 1.5VIN⎠ η(%) = 100 14 2806.2006.04.1.8 Dual High Efficiency Charge Pump for White LED and Flash Applications Ordering Information Package TDFN44-16 AAT2806 Marking1 NPXYY Part Number (Tape and Reel)2 AAT2806IXN-4.5-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/pbfree. Package Information Index Area (D/2 x E/2) TDFN44-16 Detail "B" 4.00 ± 0.05 3.30 ± 0.05 0.3 ± 0.10 0.16 0.375 ± 0.125 0.075 ± 0.075 0.1 REF Detail "A" Top View Bottom View Pin 1 Indicator (optional) 7.5° ± 7.5° + 0.05 0.8 -0.20 0.229 ± 0.051 Detail "B" Option A: C0.30 (4x) max Chamfered corner Option B: R0.30 (4x) max Round corner 0.05 ± 0.05 Side View All dimensions in millimeters. Detail "A" 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 2806.2006.04.1.8 0.23 ± 0.05 0.45 ± 0.05 4.00 ± 0.05 2.60 ± 0.05 15 Dual High Efficiency Charge Pump for White LED and Flash Applications AAT2806 © 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. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. 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 16 2806.2006.04.1.8