AAT3119IJS-4.5-T1

High Efficiency 2X Charge Pump General Description The AAT3119 is a general purpose high efficiency voltage regulated charge pump IC that can produce output current levels up to 150mA. As a voltage regulated output device, it may be used for general voltage boost applications or to power white, RGB, or flash type LEDs from a 2.7V to 5.5V input. The voltage doubling charge pump architecture of the AAT3119 provides for a low external part count; just three small ceramic capacitors are needed. This makes the AAT3119 ideally suited for small battery-powered applications. This device operates from a fixed high frequency 1.2MHz oscillator which enables the use of very small external capacitors, one 1μF flying capacitor, and two 1μF bypass capacitors at IN and OUT. The AAT3119 has built-in soft-start circuitry which prevents excessive inrush current from the source supply during startup. A low-current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1.0μA when the device is disabled. The AAT3119 is available in a Pb-free, 8-pin SC70JW package and is rated over the -40°C to +85°C temperature range. AAT3119 Features • • • • • • • • • • • ChargePump™ VIN Range: 2.7V to 5.5V 150mA of Output Current — Peak Current up to 250mA Regulated Output Voltage 1.2MHz Switching Frequency Low Noise Constant Frequency Operation 4.0V Startup ENABLE (1V/div) ILOAD = 150mA @ VIN = 3.3V ILOAD = 100mA @ VIN = 3.0V VOUT (1V/div) ILOAD = 150mA @ VIN = 3.3V Supply Voltage (V) Time (100μs/div) 8 3119.2007.02.1.2 High Efficiency 2X Charge Pump Typical Characteristics _ AAT3119 VIN vs. VIH 1.00 0.95 0.90 0.85 -40°C +25°C 1.00 0.95 0.90 0.85 -40°C +25°C AAT3119 VIN vs. VIL VIH (V) 0.75 0.70 0.65 0.60 0.55 0.50 VIL (V) 0.80 0.80 0.75 0.70 0.65 0.60 0.55 0.50 +85°C +85°C 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Supply Voltage (V) Supply Voltage (V) VEN Threshold vs. Supply Voltage 1.00 0.95 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 VEN Threshold (V) 0.90 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 2.7 3.1 VIH VIL 3.5 3.9 4.3 4.7 5.1 5.5 Supply Voltage (V) Temperature (°C) 3119.2007.02.1.2 9 High Efficiency 2X Charge Pump Functional Block Diagram C1+ IN C1- AAT3119 Charge Pump OUT Soft Start 1MHz Oscillator Voltage Reference EN GND Functional Description The AAT3119 is a 5.0V or 4.5V regulated voltage doubling charge pump device intended for general applications that require low noise voltage boost function from input supplies ranging from 2.7V to 5.5V. The charge pump is capable maintaining the regulated voltage output for continuous output current loads up to 150mA. This makes the AAT3119 ideal for general purpose voltage boost applications, driving white and RGB color LEDs, as well as USB OTG VBUS supplies in portable products. The AAT3119 charge pump and regulation circuit is also capable of supplying peak pulse currents up to 250mA for 500ms. This makes the device suitable for many photo-flash LED applications. The AAT3119 accomplishes the voltage boost function by utilizing a voltage doubling (2X) charge pump. The charge pump block within the device uses low RDS MOSFET switches to transfer charge from the input to output via a flying capacitor (CFLY). This switching process is performed over two phases of each clock cycle which is set by the fixed 1.2MHz internal oscillator. On the first phase of each clock cycle, the flying capacitor is placed in parallel with the input (IN) and is charged to the level of the input voltage across CIN. On the second phase of the switching cycle, the flying capacitor is reconfigured by the internal switches and placed in series with the input capacitor. CIN and CFLY are then placed across the output capacitor (COUT). The voltage seen on COUT is then two times that of CIN. The AAT3119 contains an internal reference and feedback system that senses the charge pump output and controls the charge pump function to maintain an accurate regulated output voltage. Because of the fixed 1.2MHz high frequency internal oscillator, the input, output, and flying capacitors are very small. This circuit architecture requires only one 1μF ceramic capacitor for the charge pump flying capacitor (CFLY) and one 1μF ceramic capacitor for both CIN and COUT. The AAT3119 has a soft-start circuit to prohibit inrush current when the device is enabled. This feature guarantees a smooth transition to the desired output voltage when the device is turned on. The system soft-start circuit is particularly useful in white LED backlight applications where the use of a PWM signal is employed as an LED dimming function. In limiting the input inrush current each time the device is turned on, the soft-start circuit helps minimize back-injected switching noise and transient supply current. 10 3119.2007.02.1.2 High Efficiency 2X Charge Pump In the operating state, the AAT3119 typically consumes 2mA of quiescent operating current. The enable pin (EN) is an active high input. When pulled low, the AAT3119 is shut down, the quiescent current drops to less than 1μA, and the output is disconnected from the input. AAT3119 Capacitor Selection Careful selection of the three external capacitors (CIN, CFLY, and COUT) is important because they will affect turn-on time, output ripple, efficiency, and load transient response. 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 three capacitors is a good starting point when designing with the AAT3119. This not only provides for a very small printed circuit board area, but cost is further reduced by the minimized bill of materials. Charge Pump Efficiency The core of the AAT3119 is a regulated output voltage doubling charge pump. The efficiency (η) for an ideal voltage doubling charge pump can typically be expressed as the output power divided by the input power: η= POUT PIN Input Capacitor A 1μF multilayer ceramic chip capacitor is suggested for the input. This capacitor should be connected between the IN pin and ground. 1μF should be suitable for most applications. Even though the AAT3119 switching ripple and noise are very low, back-injected line noise may be further reduced by increasing the value of CIN. Other types of capacitors may be used for CIN at the cost of compromised circuit performance. In addition, with an ideal voltage doubling charge pump, the output current may be expressed as half the input current. The expression to define the ideal efficiency (η) can be rewritten as: V POUT VOUT × IOUT = = OUT PIN VIN × 2IOUT 2VIN η= -or⎛ VOUT ⎞ ⎝ 2VIN ⎠ Output Capacitor The output capacitor (COUT) should be connected between the OUT pin and ground. A 1μF ceramic capacitor is also suggested in this position. Switching noise and ripple seen on the charge pump output increases with load current. Typically 1μF is sufficient for minimizing output ripple seen by the load circuit. If the load current in an application is low, or if higher levels of switching ripple can be tolerated, COUT can be reduced as low as 0.33μF. If application circuits with greater load current demands require lower switching ripple amplitudes, COUT may be increased to values above 1μF. Capacitor types other than ceramic capacitors can be used for COUT. However, capacitors comprised of materials other than ceramic will typically have a greater value of ESR, resulting in increased output switching ripple. η(%) = 100 For a charge pump with an output of 5.0 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. 3119.2007.02.1.2 11 High Efficiency 2X Charge Pump Flying Capacitor Due to the switching operation of the voltage doubling circuit topology, current flow through the flying capacitor is bi-directional. The flying capacitor selected must be a non-polarized type. A 1μF low ESR ceramic capacitor is ideal for this application. AAT3119 Applications Information White LED Backlight Driver LED Selection: In applications where the AAT3119 is utilized as a white LED backlight driver, LEDs with forward voltages up to 5.0V may be used. The AAT3119 is available in two regulated output voltage versions: 4.5V and 5.0V. The output voltage option selected will determine the maximum LED forward voltage that can be driven. The trade-off for the lower 4.5V output voltage version is the device’s ability to supply greater output current. Refer to the "Output Voltage vs. Output Current" curves in the Typical Characteristics section of this datasheet to determine the best AAT3119 output voltage option based on the requirements of a given application. LED Ballast Resistors: To set the maximum brightness of white LEDs connected in parallel from a voltage source supply, a ballast resistor connected between each LED cathode and ground is required. Refer to the application schematic in Figure 1. The maximum brightness is determined by the forward current (IF) through the respective LED for a given forward voltage (VF). The typical forward voltage of a specific LED is usually stated in the typical characteristics of the given LED manufacturer's datasheet. The correct ballast resistor value can be determined by the following equation: (VOUT - VF) IF Capacitor Characteristics Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3119. 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. Equivalent Series Resistance: ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor that is determined 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 typically have tight tolerance and are stable over temperature. Large 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 large capacitors are not required in most AAT3119 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. RB = Where: RB VF IF = = = Ballast resistor value in ohms (Ω) Regulated charge pump output voltage LED forward voltage at the desired forward current Desired LED forward current VOUT = 12 3119.2007.02.1.2 High Efficiency 2X Charge Pump CFLY 1μF AAT3119 C1+ C1- IN VBATTERY CIN 1μF OUT COUT 1μF D1 D2 D3 D4 D5 D6 AAT3119 Enable EN GND RB1 RB2 RB3 RB4 RB5 RB6 Figure 1: White LED Driver. Flash LED Driver The AAT3119 can source 250mA for pulsed loads up to 500ms from an input supply as low as 3.3V. This makes the device well suited for low-cost flash LED driver applications in portable products. Typically the 4.5V output version of the AAT3119 should be selected for photo-flash LED applications, as it can maintain better voltage regulation at higher pulsed load current levels (refer to Figure 2). The limitation of this option is that the greatest flash LED forward voltage (VF) that can be driven is 4.5V at the maximum set forward current (IF) for the application. Flash LEDs with forward voltage (VF) levels up to 5.0V can be driven by the AAT3119 5.0V output option. However, the maximum current for a 500ms pulse will be reduced. Refer to the Typical Characteristics curves for peak output current levels for a given minimum input voltage. The forward current (IF) through the flash LED may be determined with the use of a series ballast resistor. The typical forward voltage (VF) for the flash LED in a given application should be derived from the LED manufacturer's datasheet for the desired forward current (IF) of the flash application. Once the forward current has been determined, the flash ballast resistor can be calculated using the following equation: (VOUT - VF) IF RF = Where: RF = Flash ballast resistor value in ohms (Ω) Regulated charge pump output voltage (typically 4.5V) Flash LED forward voltage at the desired forward current Desired flash LED forward current VOUT = VF IF = = The flash LED function can be controlled by the AAT3119 enable pin in most applications. The device start-up time into a maximum load is about 200μs, thus eliminating the need for pre-flash control synchronization. 3119.2007.02.1.2 13 High Efficiency 2X Charge Pump CFLY 1 μF AAT3119 4.5V VIN CIN 1μF IN OUT COUT 1μF AAT3119 RF Enable EN GND Flash LED Figure 2: Flash LED Application. If a "light" or "movie" mode is also needed along with the flash function, this can be accomplished with the addition of a second ballast resistor with a flash function gating MOSFET switch as shown in Figure 3. Refer to the following equations for the calculation of flash and light resistors, RF and RL. (VOUT - VF) RL = IF RF = (VOUT - VF) - RDS IF Where: RF RDS = = Flash ballast resistor value in ohms (Ω) Flash gating MOSFET on resistance Regulated charge pump output voltage (typically 4.5V) Flash LED forward voltage at the desired forward current Desired flash LED forward current VOUT = VF = = Where: RL = Light mode ballast resistor value in ohms (Ω) Regulated charge pump output voltage (typically 4.5V) Flash LED forward voltage at the desired forward current Desired flash LED forward current in the "light" mode IF VOUT = VF IF = = 14 3119.2007.02.1.2 High Efficiency 2X Charge Pump CFLY 1μF AAT3119 4.5V VIN CIN 1μF IN OUT COUT 1μF AAT3119 Enable EN GND Flash LED RL RF Flash Enable Figure 3: Flash LED Driver with Gated Flash Application. Layout Considerations For the AAT3119, the high charge pump switching frequencies and large peak transient currents require careful printed circuit board layout. As a general rule for charge pump boost converters, the three external capacitors should be located as closely as possible to the device package with minimum length trace connections. Maximize ground plane around the AAT3119 charge pump and make sure all external capacitor are connected to the immediate power ground plane. A local component side ground plane is recommended. If this is not possible due to layout area limitations, assure good ground connections by the use of large or multiple printed circuit board vias. Refer to the basic AAT3119 evaluation board layout shown in Figure 4 and the evaluation board schematic shown in Figure 5 for an example of the recommended charge pump layout design. 3119.2007.02.1.2 15 High Efficiency 2X Charge Pump AAT3119 Figure 4: AAT3119 Evaluation Board Top Side Layout. JP1 VIN GND 2 1 C1 1μF R5 100K U1 1 4 2 IN EN AAT3119 JP2 3 EN C+ OUT 1 2 VOUT GND C3 1μF C2 1 μF GND GND C- GND 5 DS1 DS2 DS3 DS4 6 7 8 R1 49.9 R2 49.9 R3 49.9 R4 49.9 Figure 5: AAT3119 Evaluation Board Schematic Diagram. 16 3119.2007.02.1.2 High Efficiency 2X Charge Pump Quantity Designator Description 1 1 4 2 1 4 3 U1 R5 R1, R2, R3, R4 JP1, JP2 EN DS1, DS2, DS3, DS4 C1, C2, C3 High Efficiency 2X Charge Pump 100K 5% 1/8 W 0603 49.9Ω 1/8W 0805 Header, 2-Pin 2mm Test Pin White LED Capacitor 1 μF AAT3119 Value Footprint Manufacturer Part Number SC70JW-8 100K 49.9 0603 0805 HDR1X2 PIN1 LED1206 0603 Vishay Vishay Sullin Mill Max Osram Murata AAT3119 CRCW----1003F CRCW---49R9F S2105-40-ND 6821-0-0001-00-00-08-0 LW-M673 ECJ-1VB1AK05K Table 1: AAT3119 Evaluation Board Bill of Materials. 3119.2007.02.1.2 17 High Efficiency 2X Charge Pump Ordering Information Package SC70JW-8 SC70JW-8 AAT3119 Marking1 MUXYY MVXYY Part Number (Tape and Reel)2 AAT3119IJS-4.5-T1 AAT3119IJS-5.0-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 SC70JW-8 0.50 BSC 0.50 BSC 0.50 BSC 1.75 ± 0.10 0.225 ± 0.075 2.00 ± 0.20 2.20 ± 0.20 0.048REF 0.85 ± 0.15 1.10 MAX 0.15 ± 0.05 0.100 7 ° ± 3° 0.45 ± 0.10 2.10 ± 0.30 4° ± 4° All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is held on part numbers listed in BOLD. 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 18 3119.2007.02.1.2 0.05 ± 0.05