AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications General Description Features 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 8-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. 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 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. • • • Color (RGB) Lighting White LED Backlighting White LED Photo Flash The AAT2806 is available in a space-saving, thermally-enhanced TDFN44-16 package and is rated over the -40°C to +85°C temperature range. Typical Application C1 1µF C2 1µF C3 1µF C1+ C1- C2+ C2- C3+ C3- VOUT_FLASH VOUT_FL COUT 1µF VIN VIN AAT2806 CIN 1µF Backlight VOUT_BL D1 EN/SET EN_FLSH D2 D3 D4 EN/SET EN_FLSH GND 2806.2005.07.1.4 Flash D1 D2 D3 D4 COUT 1µF 1 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Pin Descriptions Pin # Symbol Function 1 2 3 C3C3+ VOUT_FL 4 5 6 7 8 9 10 VIN D4 D3 D2 D1 GND EN/SET 11 12 13 C1+ C1VOUT_BL 14 15 16 EP C2+ C2EN_FLSH Flying capacitor 3 negative terminal. Flying capacitor 3 positive terminal. Connect a 1µF capacitor between C3+ and C3-. Regulated output voltage for 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 white LED. 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 2 1 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 EN_FLSH C2C2+ VOUT_BL C1C1+ EN/SET GND 2806.2005.07.1.4 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Absolute Maximum Ratings1 Symbol VIN VEN/SET; EN_FL TLEAD Description Input Voltage EN/SET; EN_FL to GND Voltage Maximum Soldering Temperature (at leads, 10 sec) Value Units -0.3 to 6.0 -0.3 to VIN + 0.3 300 V V °C Value Units 2.0 50 W °C/W Thermal Information Symbol PD θJA Description 2, 3 Maximum Power Dissipation Maximum Thermal Resistance2 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. 2806.2005.07.1.4 3 AAT2806 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 at TA = 25°C. Symbol Description Conditions Min Typ Max Units Input Power Supply VIN ICC ISHDN IDX I(D-Match) RSINK VOUT_FL IOUT_FL TSS FCLK VEN(L) VEN(H) TEN/SET LO TEN/SET HI TOFF TLAT II Operation Range Operating Current Shutdown Current Input Current Accuracy2, 4 Current Matching Between Any Two Current Sink Inputs2, 5 Sink Switch Impedance (each)2 Flash Charge Pump Output Voltage Maximum Continuous IOUT Maximum Pulsed IOUT Soft-Start Time Clock Frequency Enable Threshold Low Enable Threshold High EN/SET Low Time Minimum EN/SET High Time EN/SET Off Timeout EN/SET Latch Timeout Enable and EN/SET Input Leakage 2.7 1X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load Current; EN_FLSH = GND, EN/SET = VIN 1.5X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load Current; EN_FLSH = GND, EN/SET = VIN 2X Mode, 3.0 ≤ VIN ≤ 5.5, Active, No Load Current; EN_FLSH = GND, EN/SET = VIN EN_FLSH = GND, 50µA Output Setting, 1X Mode 3.0 ≤ VIN ≤ 5.5, No Load Current; EN_FLSH = VIN, EN/SET = GND EN_FLSH = EN/SET = 0 ISET = 20mA and ISET = 4.1mA; TA = 25°C VD1:D4 = 3.6, VIN = 3.5V 3.0V < VIN < 5V, IOUT = 100mA; EN_FLSH = VIN 3.0V < VIN < 5V, IOUT = 150mA; EN_FLSH = VIN VIN = 3.6V; VOUT = 4.5V; EN_FLSH = VIN VIN = 3.6V; VOUT = 4.5V; IPULSED < 500mS 0.3 5.5 1 1.0 3.0 2.0 3.7 50 2.0 -10 mA µA 4.5 mA 1.0 10 µA % % 0.5 Ω 4.32 7 4.5 4.68 4.3 4.5 4.7 120 250 V mA 100 1.0 0.4 1.4 0.3 75 50 -1.0 V 500 500 1.0 µs MHz V V µs ns µs µs µA 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. Specification applies only to the charge pump doubler. 4. Determined by the sum of all active channels 5. Current matching is defined as the deviation of any sink current at IOUT = 20mA and 2mA. 4 2806.2005.07.1.4 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–Flash Driver Charge Pump Section Output Voltage vs. Output Current Maximum Current Pulse vs. Supply Voltage (VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND) Output Voltage (V) 4.60 4.56 4.52 3.6V 4.48 3.0V 3.3V 4.44 2.7V 4.40 0.1 1.0 10.0 100.0 1000.0 Maximum Current Pulse (mA) (VOUT_FL = 4.5V; EN_FL = VIN; EN/SET = GND) 450 400 One-shot pulse duration = 250ms VOUT > 4.0V 350 300 250 200 150 100 50 0 3.0 3.1 3.2 3.3 3.4 3.6 3.7 3.8 Output Current (mA) Supply Voltage (V) Startup Time Startup Time (50mA Load) (100mA Load) EN_FLSH (1V/div) EN_FLSH (1V/div) VOUT_FL (1V/div) VOUT_FL (1V/div) 100µ µs/div 3.9 4.0 4.1 4.2 100µ µs/div Load Response vs. Time Load Response vs. Time (50mA Load) (100mA Load) VIN = 3.5V VIN = 3.5V VOUT_FL (10mV/div) VOUT_FL (10mV/div) IOUT (20mA/div) IOUT (50mA/div) 5ms/div 2806.2005.07.1.4 3.5 5ms/div 5 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–Flash Driver Charge Pump Section Output Ripple Voltage vs. Time Output Ripple Voltage vs. Time (IOUT = 50mA @ VIN = 3.5V) (IOUT = 100mA @ VIN = 3.5V) VIN (10mV/div) VIN (10mV/div) VOUT (10mV/div) VOUT (20mV/div) IIN (10mA/div) IIN (10mA/div) 500ns/div 500ns/div Supply Current vs. Supply Voltage Oscillator Frequency vs. Supply Voltage 2.75 2.50 Oscillator Frequency (MHz) Supply Current (mA) 3.00 IOUT = 0µA C3 = 1µF VEN_FL = VIN 2.25 2.00 1.75 1.50 1.25 1.00 2.5 3.0 3.5 4.0 Supply Voltage (V) 6 4.5 5.0 1.30 1.25 +25°C 1.20 1.15 +85°C -40°C 1.10 2.7 3.2 3.7 4.2 4.7 Supply Voltage (V) 2806.2005.07.1.4 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–White LED Backlight Driver Section Turn-On to 1X Mode Turn-On to 1.5X Mode (VIN = 4.2V; 20mA Load) (VIN = 3.5V; 20mA Load) EN (2V/div) EN (2V/div) CP (2V/div) VSINK (500mV/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) IIN (200mA/div) 100µ µs/div 100µ µs/div Turn-On to 2X Mode Turn-Off from 1.5X Mode (VIN = 2.8V; 20mA Load) (VIN = 3.5V; 20mA Load) EN (2V/div) EN (2V/div) VF (1V/div) CP (2V/div) VSINK (500mV/div) IIN (100mA/div) IIN (200mA/div) 100µ µs/div 500µ µs/div Efficiency vs. Supply Voltage Current Matching vs. Temperature 100 20.4 20mA VF = 3.4V 10mA VF = 3.1V Current (mA) Efficiency (%) Channel 2 20.2 90 80 70 60 20.0 Channel 4 19.8 Channel 3 Channel 1 19.6 19.4 19.2 19.0 50 2.8 3.0 3.2 3.4 3.6 Supply Voltage (V) 2806.2005.07.1.4 3.8 4.0 4.2 -40 -20 0 20 40 60 80 Temperature (°°C) 7 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Typical Characteristics–White LED Backlight Driver Section Load Characteristics Load Characteristics (VIN = 3.7V; 1.5X Mode; 14mA Load) (VIN = 2.7V; 2X Mode; 14mA Load) VIN (40mV/div) VIN (40mV/div) CP (40mV/div) CP (40mV/div) VSINK (40mV/div) VSINK (40mV/div) 500ns/div 500ns/div Load Characteristics Load Characteristics (VIN = 3.9V; 1.5X Mode; 20mA Load) (VIN = 2.9V; 2X Mode; 20mA Load) VIN (40mV/div) VIN (40mV/div) CP (40mV/div) CP (40mV/div) VSINK (40mV/div) VSINK (40mV/div) 500ns/div 500ns/div EN/SET Off Timeout vs. Input Voltage 8 400 350 300 250 -40°C 200 150 100 25°C 85°C 50 0 EN/SET Off Timeout (µ µs) EN/SET Latch Timeout (µ µs) EN/SET Latch Timeout vs. Input Voltage 350 300 -40°C 250 200 150 25°C 85°C 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 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) 2806.2005.07.1.4 AAT2806 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 vs. Input Voltage Enable Threshold High (V) 18 Amplitude (mV) 16 14 12 20mA 10 8 6 4 10mA 2 0 2.50 2.67 2.84 3.01 3.18 3.35 3.52 3.69 3.86 4.03 4.20 Input Voltage (V) 1.2 1.1 1 -40°C 0.9 0.8 0.7 0.6 25°C 85°C 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 Input Voltage (V) Enable Threshold Low (V) Enable Threshold Low vs. Input Voltage 1.2 1.1 1 0.9 -40°C 0.8 0.7 0.6 25°C 0.5 85°C 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 Input Voltage (V) 2806.2005.07.1.4 9 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Functional Block Diagram C3+ C3- Soft-Start 2X Charge Pump EN_FLSH 1MHz Oscillator VOUT_FLSH VIN VREF C1+ Soft-Start Control 1X 1.5X 2X Charge Pump 1MHz Oscillator Voltage Reference Control Logic C2+ C2VOUT_BL 6 X 16 Bit ROM EN/SET C1- 6 X 16 Bit ROM D/A D1 D/A D2 D/A D3 D/A D4 GND 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 10 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-D3 to be controlled independently from the LED sub-channel D4. 2806.2005.07.1.4 AAT2806 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 backlight charge pump output capacitor (COUT), and one 1µF ceramic capacitor for flash charge pump output capacitor (COUT). 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 13-16). 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. 2806.2005.07.1.4 Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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 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 13-16). 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. 11 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications S2Cwire Serial Interface Timing Diagram T HI TLO TOFF TLAT EN/SET 1 Data Reg 2 n-1 n ≤ 16 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. 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. 12 n 0 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 in-rush currents during start up of the charge pump circuit. 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) (<100mΩ) 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. 2806.2005.07.1.4 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Capacitor Characteristics Charge Pump Power Efficiency 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. 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. Equivalent Series Resistance ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor, which 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 COG materials. NPO and COG materials typically have tight tolerance and are stable over temperature. Larger capacitor values are typically composed of X7R, X5R, Z5U, or Y5V dielectric materials. Large ceramic capacitors, typically greater than 2.2µF, are often available in low-cost Y5V and Z5U dielectrics, but capacitors greater than 1µF are typically not 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. 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." 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: η= 2806.2005.07.1.4 POUT PIN 13 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications The expression to define the ideal efficiency (η) can be rewritten as: η= POUT VOUT × IOUT VOUT = = PIN VIN × IOUT VIN -or- η(%) = 100 ⎛ VOUT ⎞ ⎝ VIN ⎠ 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= POUT PIN 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: η= POUT VOUT × IOUT VOUT = = PIN VIN × 1.5IOUT 1.5VIN For a charge pump with an output of 5 volts and a nominal input of 3.5 volts, 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 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: η= POUT VOUT × IOUT VOUT = = PIN VIN × 2.0IOUT 2.0VIN -or- η(%) = 100 ⎛ VOUT ⎞ ⎝ 2.0VIN⎠ For a charge pump with an output of 5 volts and a nominal input of 3.0 volts, 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- η(%) = 100 14 ⎛ VOUT ⎞ ⎝ 1.5VIN⎠ 2806.2005.07.1.4 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN44-16 NPXYY 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 TDFN44-16 3.30 ± 0.05 Detail "B" 4.00 ± 0.05 Index Area (D/2 x E/2) 0.3 ± 0.10 0.375 ± 0.125 0.16 0.075 ± 0.075 0.1 REF 4.00 ± 0.05 2.60 ± 0.05 Top View Pin 1 Indicator (optional) 0.23 ± 0.05 Bottom View 0.45 ± 0.05 Detail "A" 0.229 ± 0.051 + 0.05 0.8 -0.20 7.5° ± 7.5° 0.05 ± 0.05 Detail "B" Option A: C0.30 (4x) max Chamfered corner Option B: R0.30 (4x) max Round corner Side View Detail "A" All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 2806.2005.07.1.4 15 AAT2806 Dual High Efficiency Charge Pump for White LED and Flash Applications 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, and advise customers 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. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 16 2806.2005.07.1.4