AAT3122 SKYWORKS | Alldatasheet

Document overview

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  • PDF pages: 12

Technical content

Features

  • VIN Range: 2.7V to 5.5V
  • <1µA of Shutdown Current
  • 1MHz Switching Frequency
  • Dual Mode 1X and 1.5X Charge Pump for Maximum Efficiency
  • Only Four External Components
  • Simple Serial Control (S2Cwire) Interface
  • Low Noise Constant Frequency Operation
  • 33% Less Input Current Than Doubler Charge Pumps
  • Small Application Circuit
  • Regulated Output Current
  • Automatic Soft Start
  • No Inductors
  • TSOPJW-12 Package
  • -40°C to +85°C Temperature Range

Applications

  • Programmable Current Source
  • White LED Backlighting

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 Pin Descriptions Pin # Symbol Function 1 C2+ Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-. 2 OUT Charge pump output. Requires 1µF bypass capacitor to ground. 3 C1- Flying capacitor 1 negative terminal. 4 C1+ Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-. 5, 6, 7, 8 D Output current source with drive capability of up to 120mA. 9 EN/SET Input control pin. Serial data interface that controls the level of output current. See the Application Information section of this datasheet for more details. 10 IN Input power supply. Requires 1µF bypass capacitor to ground. 11 GND Ground. 12 C2- Flying capacitor 2 negative terminal. Pin Configuration TSOPJW-12 (Top View) C2+ OUT C1- C1+ D D C2- GND IN EN/SET D D

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 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. Absolute Maximum Ratings1 Symbol Description Value Units VIN Input Voltage -0.3 to 6.0 V VOUT Charge Pump Output -0.3 to 6.0 V VEN/SET EN/SET to GND Voltage -0.3 to 6.0 V VEN/SET(MAX) Maximum EN/SET to Input Voltage 0.3 V IOUT2 Maximum DC Output Current 150 mA TJ Operating Junction Temperature Range -40 to 150 °C Thermal Information3 Symbol Description Value Units QJA Thermal Resistance 160 °C/W PD Maximum Power Dissipation (TA = 25°C)4 625 mW

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 1. The AAT3122 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla- tion with statistical process controls. Electrical Characteristics1 VIN = 3.5V; CIN = COUT = C1 = C2 = 1.0µF; TA = -40°C to +85°C. Unless otherwise noted, typical values are TA = 25°C. Symbol Description Conditions Min Typ Max Units Input Power Supply VIN Operation Range 2.7 5.5 V Icc Operating Current 3.0 ≤ VIN ≤ 5.5, Active, No Load Current 1.8 3.5 mA ISHDN Shutdown Current EN = 0 1.0 µA ID Maximum Output Current VIN = 3.5V; Code = 32 108 120 132 mA Charge Pump TSS Soft-Start Time 200 µs FCLK Clock Frequency 1000 kHz hCP Charge Pump Efficiency VIN = 3.6V, IOUT(Total) = 120mA; Measured from IN to OUT 93 % EN/SET VEN(L) Enable Threshold Low VIN = 2.7V to 5.5V 0.5 V VEN(H) Enable Threshold High VIN = 2.7V to 5.5V 1.4 V TLO EN/SET Low Time 0.3 75 µs THI Minimum EN/SET High Time 50 ns TOFF EN/SET Off Timeout 500 µs Input Current EN/SET Input Leakage -1.0 1.0 µA

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 Typical Characteristics Unless otherwise noted, VIN = 3.6V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C. Efficiency vs. VIN (ID = 80mA) 100 VIN (V) Efficiency (%) VDIODE = 3.3V VDIODE = 3.4V VDIODE = 3.5V VDIODE = 3.6V IDIODE vs. VIN VIN (V) IDIODE (mA) VDIODE = 3.3V VDIODE = 3.4V VDIODE = 3.5V VDIODE = 3.6V Quiescent Current vs. VIN 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 VIN (V) Quiescent Current (mA) VDIODE = 3.3V VDIODE = 3.4V VDIODE = 3.5V VDIODE = 3.6V VIH and VIL vs. VIN 0.600 0.625 0.650 0.675 0.700 0.725 0.750 0.775 0.800 0.825 0.850 VIN (V) VIH VIL Turn-On to Full-Scale Charge Pump Time (50µs/div) ENSET (1V/div) OUT (2V/div) VDIODE (1V/div) IIN (200mA/div) Turn-On to Full-Scale Load Switch Time (50µs/div) ENSET (1V/div) OUT (2V/div) VDIODE (2V/div) IIN (100mA/div)

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 Typical Characteristics Unless otherwise noted, VIN = 3.6V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C. Charge Pump to Load Switch (80mA) Time (50µs/div) VIN (10mV/div) OUT (2V/div) VDIODE (2V/div) IIN (100mA/div) Load Switch to Charge Pump (80mA) Time (50µs/div) VIN (20mV/div) OUT (1V/div) VDIODE (1V/div) IIN (200mV/div) Turn-Off Time (200µs/div) ENSET (1V/div) VDIODE (2V/div) IIN (100mA/div) 80mA Load Characteristics Time (1µs/div) 20mV/div VIN OUT VDIODE

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 Functional Block Diagram Voltage Reference Soft Start 1MHz Oscillator 1.5X Charge Pump S 2 Cwire Interface 32x8 bit ROM Current Mode DAC VIN C1+ C1- C2+ C2- OUT D GND EN/SET Functional Description The AAT3122 is a dual mode load switch (1X) and high efficiency (1.5X) fractional charge pump device intended for white LED backlight applications. The fractional charge pump consists of a low dropout linear voltage regulator followed by a 1.5X charge pump. To maximize power conversion efficiency, an internal feedback control sensing circuit monitors the voltage required on the con- stant current source output. This control circuit then sets the load switch and charge pump functions based upon the input voltage level versus the output voltage level needed. This function significantly enhances overall device efficiency when the input voltage level is greater than the voltage required at the constant current source output. Switchover between the 1.5X (charge pump) operating mode and the 1X (load switch) mode occurs automatically (as a function of input and output voltages) and does not require user intervention to maintain max- imum efficiency. The AAT3122 requires only four external components: two 1µF ceramic capacitors for the charge pump flying capacitors (C1 and C2), one 1µF ceramic capacitor for CIN, and one 0.33µF to 1µF ceramic capacitor for C OUT. The LDO/1.5X charge pump output is converted into a con - stant current output capable of driving up to six indi - vidual LEDs with a maximum of 20mA each. The current source output magnitude is controlled by the EN/SET serial data S2Cwire interface. The interface records rising edges of the EN/SET pin and decodes them into 32 indi- vidual current level settings each 1dB apart. This is sum- marized in Figure 1 and Table 1. Code 32 is full scale, and Code 1 is full scale attenuated by 31dB. The modu - lo 32 interface wraps states back to State 1 after the 32nd clock.

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 Normalized Current Level Settings 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 12 34 56 78 91 01 11 21 31 41 51 61 71 81 92 02 12 22 32 42 52 62 72 82 93 03 13 2 Code Normalized Current to Full Scale Figure 1: Normalized Current Level Settings. Applications Information Current Level Settings LED current level is set via the serial interface according to a logarithmic scale, where each code is 1dB greater than the previous code. In this manner, the LED bright - ness appears linear with each increasing code. Table 1 depicts the relationship between each rising edge of the EN/SET and the output current in mA. Code IOUT (mA) Code IOUT (mA) 1 3.3 17 21.2 2 3.8 18 24.0 3 4.2 19 26.8 4 4.7 20 30.1 5 5.2 21 33.9 6 6.1 22 38.1 7 6.6 23 42.4 8 7.5 24 47.5 9 8.5 25 53.6 10 9.4 26 60.2 11 10.8 27 67.3 12 11.8 28 75.8 13 13.6 29 84.7 14 15.1 30 95.1 15 16.9 31 106.8 16 18.8 32 120.0 Table 1: Current Level Settings. EN/SET Serial Interface The current source output magnitude is controlled by the EN/SET serial interface. The interface records rising edges of the EN/SET pin and decodes them into 32 indi- vidual current level settings each 1dB apart. Code 32 is full scale, and Code 1 is full scale attenuated by 31dB. The modulo 32 interface wraps states back to State 1 after the 32nd clock, so 1dB of attenuation is achieved by clocking the EN/SET pin 31 times. The counter can be clocked at speeds up to 1MHz, so intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to 3.3mA, the lowest setting. 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 after the EN/SET pin transitions to a logic low state. The EN/SET timing is designed to accommodate a wide range of data rates. After the first rising edge of EN/SET, the charge pump is enabled and reaches full capacity after the soft-start time (TSS). During the soft-start time, multiple clock pulses may be entered on the EN/SET pin to set the final output current level with a single burst of clocks. Alternatively, the EN/SET clock pulses may be entered one at a time to gradually increase the LED brightness over any desired time period. A constant cur- rent is sourced as long as EN/SET remains in a logic high state. The current source outputs are switched off after EN/SET has remained in a low state for at least the T OFF timeout period.

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 EN/SET Timing Diagram EN/SET Code 1 2 3 OFFOFF tHI tLO tOFF LED Selection The AAT3122 is specifically intended for driving white LEDs. However, the device design will allow the AAT3122 to drive most types of LEDs with forward voltage speci - fications ranging from 2.0V to 4.3V. LED applications may include main and sub-LCD display backlighting, camera photo-flash applications, color (RGB) LEDs, infrared (IR) diodes for remotes, and other loads bene - fiting from a controlled output current generated from a varying input voltage. Device Switching Noise Performance The AAT3122 operates at a fixed frequency of approxi - mately 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 induc- tor-based DC/DC boost converter white LED backlight solutions. The AAT3122 soft-start feature prevents noise transient effects associated with inrush currents during start-up of the charge pump circuit. Power Efficiency and Device Evaluation Due to the unique charge pump circuit architecture and design of the AAT3122, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the AAT3122 output is purely a constant current source, it is difficult to measure the output voltage 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 component count, reliability, operating range, and total energy usage...not just % efficiency. Charge Pump Efficiency The AAT3122 is a fractional charge pump. The efficiency (h) can be simply defined as a linear voltage regulator with an effective output voltage that is equal to one and a half times the input voltage. Efficiency (h) 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 ( h) can be rewritten as: η = POUT = VOUT · IOUT = VOUT PIN VIN · 1.5IOUT 1.5VIN η(%) = 100 VOUT 1.5VIN

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 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 con - sumption, the actual efficiency can be measured at 93%. These figures are in close agreement for output load conditions from 3.0mA to 120mA. Efficiency will decrease as load current drops below 0.05mA or when the level of VIN approaches VOUT. Refer to the Typical Characteristics section of this datasheet for measured plots of efficiency versus input voltage and output load current for the given charge pump output voltage options. Capacitor Selection Careful selection of the four external capacitors C IN, C1, C2, and COUT is important because they will affect turn-on time, output ripple, and transient performance. Optimum performance will be obtained when low ESR ceramic capacitors are used. In general, low ESR may be defined as less than 100mW. When choosing the four capacitors, a capacitor value of 1µF is a good starting point. If the LED current sources are only programmed for light cur - rent levels, then the capacitor size may be decreased. Capacitor Characteristics Ceramic composition capacitors are highly recommend - ed over all other types of capacitors for use with the AAT3122. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counter - parts. 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 capaci - tors 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 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 materi - als. 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 dielec- tric 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 the AAT3122 application. Capacitor area is another contributor to ESR. Capacitors that are physically large will have a lower ESR when com- pared 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 AAT3122 has a thermal protection circuit that will shut down the charge pump and current outputs if the die temperature rises above the thermal limit due to short- circuit conditions.

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 * In some applications, white LED forward voltages (VF) can vary significantly. Ballast resistors between the LED cathodes and ground are recommended for balancing the forward voltage differences. The ballast resistor value may be approximated by the following equation: RB = (VIN(MIN))1.5 - (VF(MAX) + 250mV) IF(MAX) V F(MAX) = Maximum expected LED forward voltage at the given maximum forward current level. Refer to the LED manufacturers’ datasheet for maximum VF specifications. I F(MAX) = Maximum forward current used to drive an individual LED. V IN(MIN) = Minimum input supply voltage for the application. R B = Ballast resistor value in ohms. Additional Application Circuit CIN 1µF VBATTERY COUT 1µF EN/SET 1µF 1µF D2 D3 D4 D5 VIN VOUT C1+ C1- C2+ C2- EN/SET GND AAT3122 *In some applications, white LED forward voltages (VF) can vary significantly. Ballast resistors between the LED cathodes and ground are recommended for balancing the forward voltage differences. The ballast resistor value may be approximated by the following equation: RB = VSOURCE - VF IF

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 202132A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012 Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Sky - works may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided here- under, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale. THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, IN - CLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or en- vironmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of pub- lished parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters. Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.

Ordering Information

Package Marking1 Part Number (Tape and Reel)2 TSOPJW-12 JEXYY AAT3122ITP-T1 Skyworks Green™ products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of Green™, document number SQ04-0074.

Package Information

0.20 + 0.10 - 0.05 0.055 ± 0.045 0.45 ± 0.15 7° NOM 4° ± 4° 3.00 ± 0.10 2.40 ± 0.10 2.85 ± 0.20 0.15 ± 0.05 0.9625 ± 0.0375 1.00 + 0.10 - 0.065

0.04 REF

0.010 2.75 ± 0.25 All dimensions in millimeters.