ANALOGICTECH - AAT1239-1 40V Step-Up Converter for 4 to 10 White LEDs handbook
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1. E 85 0 4 7UH DS1 aaa a 82 5 R2 Di yon PVIN LIN 374kQ X M Y m gt 80 0 Li lon deci o g 4 ES MA nr MN AAT1239 1 a R3 2249F Pos D3 5 OVP Jaka Y Do Vos o E y 75 0 aks Ponp un Vo YDt5 o B E i sf 2 725 als gt _j EN SET FB XY yor E gt seEL AGND pi soma yor Yor 70 0 Vn 3 0V 7 els y Yos 67 5 Vin 3 6V m uk E Vy 4 2V C1 10V 0805 X5R 4 7uF GRM219R61A475KE19 x E D9 yos 65 0 l C2 50V 1206 X7R 2 2uF GRM31CR71H225KA88 L14 7uH CDRHADZ2IHP ART Jow oz 5 10 15 20 25 30 35 40 DS1 SS16L lour mA Figure 16 Enhanced Efficiency Configuration for Li ion Battery Two Branch Ten WLEDs Series Connected Application 22 www analogictech com 1239 1 2008 10 1 2 PRODUCT DATASHEET NA AAT 1239 1 lt y SwitchReg 40V Step Up Converter for 4 to 10 White LEDs Ordering Information Package Marking Part Number Tape and Reel TSOPJW 12 ZLXYY AAT1239ITP 1 T1 All AnalogicTech products are offered in Pb free packaging The term Pb free means semiconductor Pb free 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 about quality aspx Package Information2. TSOPJW 12 0 10 0 20 905 gt e A A o e 3 A eo eo H H e LO x N N Y O O Wg U U Y gt gt gt gt lt gt 0 50 BSC 0 50 BSC 0 50 BSC 0 50 BSC 0 50 BSC 7 NOM 3 00 0 10 re gt m o E o S s8 i G jes 3 E Us 2 TEHE 444 0 055 0 0454 gt 0 45 0 15 gt 2 75 0 25 All dimensions in millimeters 1 XYY assembly and date code 2 Sample stock is generally held on part numbers listed in BOLD TM Advanced Analogic Technologies Inc A N A LOGIC 3230 Scott Boulevard Santa Clara CA 95054 gt Phone 408 737 4600 Fax 408 737 4611 apy CI 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 Except as provided in AnalogicTech s terms and conditions of sale AnalogicTech assumes no liability whatsoever and AnalogicTech disclaims any express or implied warranty relating to the sale and or use of AnalogicTech products including
3. SD3814 2R2 4 0x4 0x1 0 Shielded Cooper Electronics SD3110 2R2 3 1x3 1x1 0 Shielded www cooperet com SD3118 4R7 3 1x3 1x1 8 Shielded SD3118 100 3 1x3 1x1 8 Shielded NPO3SB 2ROM 4 0x4 0x1 8 Shielded Taiyo Yuden NR3010T 2R2M 3 0x3 0x1 0 Shielded www t yuden com NPO3SB4R7 4 0x4 0x1 8 Shielded NP03SB100M 4 0x4 0x1 8 Shielded Table 4 Recommended Inductors for Various Output Levels Select Ipeak lt Isat 1239 1 2008 10 1 2 www analogictech com 17 ANALOGIC E TECH PRODUCT DATASHEET AAT 1239 SwitchReg Inductor Efficiency Considerations The efficiency for different inductors is shown in Figure 8 for ten white LEDs in series Smaller inductors yield increased DCR and reduced operating efficiency CDRH5D16F 2R2 29mQ s SD3814 2R2 77mQ Efficiency 96 o e 63 2 5 8 11 14 17 20 LED Current mA Figure 8 AAT1239 1 Efficiency for Different Inductor Types Vi 3 6V Ten White LEDs in Series Selecting the Boost Capacitors The high output ripple inherent in the boost converter necessitates low impedance output filtering Multi layer ceramic MLC capacitors provide small size and adequate capacitance low parasitic equivalent series resistance ESR and equivalent series inductance ESL and are well suited for use with the AAT1239 1 boost regulator MLC capacit
4. Evaluation Board Schematic with ten LEDs and microcontroller 20 www analogictech com 1239 1 2008 10 1 2 E y ANALOGIC TECH PRODUCT DATASHEET AAT 1239 SwitchReg Additional Applications 40V Step Up Converter for 4 to 10 White LEDs Efficiency 96 Efficiency Efficiency Efficiency vs LED Current 4 White LEDs Rej As 30 10 o Vin 4 2V Vin 3 6V Efficiency vs LED Current 8 White LEDs Rei as 30 10 T T Vin 5V Vw 4 2V Vin 3 6V Efficiency vs LED Current 9 White LEDs Reauast 30 10 T T Vin 5V St gt An ran Up to 17V chottky AAM M 30mA max R2 vo PVIN LIN 158k du Li lon C1 VIN Sw c2 y LED Jt Vp 2 7V 2 2uF D3 o 55V SENE AAT1239 1 R3 Ho Nam 12k y sx 7L LED d 4 PGND L x EN SET FB i R1 SEL AGND 1 ajio zoma Figure 12 Four LEDs In Series Configuration L1 DS1 Up to 30V 2 2uH Schottky 30mA max R2 y D1 PVIN LIN lb ale TA ey ca VIN C2 x LED yi 2 2uF D3 to 55V ENE AAT1239 1 R3 H a O 12k yo y LED PUER PGND L Y Ea 7 rd qo E
5. age threshold occurs prior to the output reaching 40V Vourmax The value of R3 should be selected from 10kQ to 20kQ to minimize losses without degrading noise immunity R R ges 1 Vove VOUT AAT1239 1 R2 OVP e Coir GND R3 cq Figure 1 Over Voltage Protection Circuit Inductor Current bottom A 8 A A e1ppru e6e3joA yndjno Over Voltage Protection Pin top V Time 4ms div Figure 2 Over Voltage Protection Open Circuit Response No LED 40V Step Up Converter for 4 to 10 White LEDs Assume R3 12kQ and Vourmax 40V Selecting 1 resistor for high accuracy this results in R2 374kQ rounded to the nearest standard value The minimum OVP threshold can be calculated R Vour ove uiv Vove min amp 1 35 4V To avoid OVP detection and subsequent reduction in the programmed output current see following section the maximum operating voltage should not exceed the minimum OVP set point Voutmax x Vour ove MIN In some cases this may disallow configurations with high LED forward voltage Vrep and or greater than ten series white LEDs Vg gp unit to unit tolerance can be as high as 15 of nominal for white LED devices OVP Constant Voltage Operation Under closed loop constant current conditions the out put voltage is determined by the operating current LED forward voltage characte
6. change without notice 1239 1 2008 10 1 2 www analogictech com 15 ANALOGIC E TECH PRODUCT DATASHEET AAT 1239 SwitchReg The maximum duty cycle can be estimated from the relationship for a continuous mode boost converter Maximum duty cycle Dmax is the duty cycle at minimum input voltage Vinmm D Vour Vinin cn Vour The average diode current is equal to the output current Invector lout The average output current multiplied by the forward diode voltage determines the loss of the output diode PiossipiopE lavector Ve lour Ve For continuous LED currents the diode junction tem perature can be estimated Tione Tame Oya PLoss DIoDE Output diode junction temperature should be maintained below 1109C but may vary depending on application and or system guidelines The diode 0 4 can be mini mized with additional PCB area on the cathode PCB heat sinking the anode may degrade EMI performance The reverse leakage current of the rectifier must be con sidered to maintain low quiescent input current and Rated Forward Non Repetitive Peak Surge Part Current Number 09 SS16L Manufacturer Current A V 40V Step Up Converter for 4 to 10 White LEDs high efficiency under light load The rectifier reverse cur rent increases dramatically at elevated temperatures Selecting the Boost Inductor The AAT1239 1 controller utilizes hysteretic control and th
7. liability or warranties relating to fitness for a particular purpose merchantability or infringement of any patent copyright or other intellectual property right In order to minimize risks associated with the customer s applications adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards 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 1239 1 2008 10 1 2 www analogictech com 23
8. 0 2R2 DS1 SS16L D1 D10 LW M673 White LED other alternatives more stability at 40V C2 50V 1206 X7R 4 7uF GRM31CR71H475K under 20V application C2 25V 0805 X7R 2 24F GRM21BR71E225KA73L Figure 4 AAT1239 1 White LED Boost Converter Schematic LED Brightness Control z The AAT1239 1 uses S Cwire programming to control LED brightness and does not require PWM pulse width dd a modulation or additional control circuitry This feature m bou a SELSHIGH greatly reduces the burden on a microcontroller or sys E ka 2d ai tem IC to manage LED or display brightness allowing 5 10 ka Aa l the user to set it and forget it With its high speed E SEL LOW ba serial interface 1MHz data rate the output current of us AA n A the AAT1239 1 can be changed successively to brighten or dim the LEDs in smooth transitions i e to fade out ar n 7 10 n 46 or in abrupt steps giving the user complete program S Cwire Data Register mability and real time control of LED brightness Figure 5 Programming AAT1239 1 LED Current with RaauasT 30 10 1239 1 2008 10 1 2 www analogictech com 13 ANALOGIC E TECH AAT 1239 PRODUCT DATASHEET SwitchReg Alternatively toggling the SEL logic pin from low to high implements stepped or pulsed LED currents by increas ing the FB pin voltage Figure 6 illustrates the SELECT pin scaling factor defined as the LED current with SEL HIGH divided by the LED current with SEL LOW In the AA
9. 1 2 PRODUCT DATASHEET es AAT 1239 1 SwitchReg 40V Step Up Converter for 4 to 10 White LEDs Typical Characteristics Efficiency vs LED Current Efficiency vs LED Current 10 White LEDs Reattast 30 10 9 White LEDs Raj As 30 10 80 78 O Oooo P YAA 7 c e 72 9 7 9 s E E s Vin 4 2V Vin 3 6V u 70 Ww Vin 4 2V _ Vn 3 6V 68 66 66 2 4 6 8 10 12 14 16 18 20 2 4 6 8 10 12 14 16 18 20 ligo mA ligo mA Shutdown Current vs Input Voltage Line Transient EN GND 10 White LEDs Reatast 30 10 1 0 7 z m l avy o o c o8 lt ZN 2 25 C as 332 S E o 0 6 LE 3 5 gt o o o 85 C 2 El 32 8 e c e o z 0 4 o 0 02 o gt gt o 3 3 p 0 6 g 3 02 23 o 5 40 C 5 058 3 0 0 9 s 24 3 1 3 5 3 9 4 3 4 7 5 1 5 5 Input Voltage V Time 50us div Accuracy l y vs Input Voltage Accuracy lep vs Temperature Vra 0 6V Reattast 30 10 Vra 0 6V Reattast 30 10 2 0 1 5 1 5 40 C 10 321 0 E 8 05 g 0 5 gt 0 0 gt 0 0 S as 25 C 85 C S J gt 05 9 10 8 lt lt 1 5 1 0 2 0 1 5 27 3 2 3 7 4 2 4 7 5 2 5 7 40 15 10 35 60 85 Input Volt
10. 2 7V to 5 5V Vra 0 6V Ros on L Low Side Switch On Resistance Ros on IN Input Disconnect Switch On Resistance Tss Soft Start Time From Enable to Output Regulation Veg 300MV Vove Over Voltage Protection Threshold Vour Rising Over Voltage Hysteresis Vour Falling Iur N Channel Current Limit Tsp T Thermal Shutdown Threshold Thys SEL EN SET VseL L T Thermal Shutdown Hysteresis SEL Threshold Low Vseh SEL Threshold High VEN SET L Enable Threshold Low VEN SET H Enable Threshold High Tenyset LO EN SET Low Time Ven ser 0 6V Ten SET HI EN SET High Time Vayser gt 1 4V Tore EN SET Off Timeout Ven ser 0 6V Tiar EN SET Latch Timeout Vayser gt 1 4V Igyser AAT1239 1 EN SET Input Leakage FB Pin Regulation Ven set 5V Vin 5V Vin 2 7V to 5 5V SEL GND EN SET DATA16 Vin 2 7V to 5 5V SEL HIGH EN SET HIGH PRODUCT DATASHEET AAT 1239 40V Step Up Converter for 4 to 10 White LEDs 1 Specification over the 40 C to 85 C operating temperature range is assured by design characterization and correlation with statistical process controls 2 Maximum continuous output current increases with reduced output voltage but may vary depending on operating efficiency and thermal limitations 4 www analogictech com 1239 1 2008 10
11. A Zetex ZHCS350 1 7x0 9x0 8 SOD523 Table 3 Typical Surface Mount Schottky Rectifiers for Various Output Levels 16 www analogictech com 1239 1 2008 10 1 2 ANALOGIC E TECH PRODUCT DATASHEET AAT 1239 SwitchReg The output inductor L is selected to avoid saturation at minimum input voltage maximum output load condi tions Peak current may be estimated using the follow ing equation assuming continuous conduction mode Worst case peak current occurs at minimum input volt age maximum duty cycle and maximum load Switching frequency Fs can be estimated from the curves and assumes a 2 2yH inductor lour Dmax V IN MIN lhe Du 2 Fg L At light load and low output voltage the controller reduces the operating frequency to maintain maximum operating efficiency As a result further reduction in output load does not reduce the peak current Minimum peak current can be estimated from 0 5A to 0 75A At high load and high output voltages the switching fre quency is somewhat diminished resulting in higher Ipeak Bench measurements are recommended to confirm actu al Ipeak and ensure that the inductor does not saturate at maximum LED current and minimum input voltage The RMS current flowing through the boost inductor is equal to the DC plus AC ripple components Under worst case RMS conditions the current waveform is critically continuous The resulting RMS calculat
12. GRM21BR71E225KA73L Murata GRM31CR71H225KA88 Murata GRM31CR71H475K Table 5 Recommended Ceramic Capacitors 18 www analogictech com 1239 1 2008 10 1 2 ez E ANALOGIC TECH PRODUCT DATASHEET AAT 1239 SwitchReg PCB Layout Guidelines Boost converter performance can be adversely affected by poor layout Possible impact includes high input and output voltage ripple poor EMI performance and reduced operating efficiency Every attempt should be made to optimize the layout in order to minimize para sitic PCB effects stray resistance capacitance and inductance and EMI coupling from the high frequency SW node A suggested PCB layout for the AAT1239 1 boost converter is shown in Figures 9 and 10 The fol lowing PCB layout guidelines should be considered 1 Minimize the distance from Capacitor C1 and C2 negative terminal to the PGND pins This is espe cially true with output capacitor C2 which conducts high ripple current from the output diode back to the PGND pins e I LIXIJ LIII C2 H p e Dc 13 SS le ED bt Ll Jet EN e Select DC It e JPL AAT12391TP DB1 Figure 9 AAT1239 1 Evaluation Board Top Side Layout with ten LEDs and microcontroller 40V Step Up Converter for 4 to 10 White LEDs Minimize the distance between L1 to DSi and switching pin SW minimize the size of the PCB area connected to the SW pin Maintain a ground plane and con
13. N SET FB e e D8 D7 D6 R1 LED LED LED gt SEL AGND A0 20m Figure 13 Eight LEDs In Series Configuration i DS1 Up to 34V E UN Schottky SUmA max R2 yo PVIN LIN 324k y m Li lon C1 VIN sw C2 Y LED L Ysay CL 22yF D to55V S AAT1239 1 R3 UE Mc OVP 12k yo A LED e PGND L e Y 5 y do EN SET FB Lau TT D9 D8 D7 D6 R1 LED LED LED LED SEL AGND aun Figure 14 Nine LEDs In Series Configuration 1239 1 2008 10 1 2 www analogictech com 21 PRODUCT DATASHEET ANALOGIC TECH SwitchReg AAT 1239 40V Step Up Converter for 4 to 10 White LEDs 90 0 L1 ouf si 87 5 SVYY R2 yo 85 0 PVIN LIN Irka io ES wo Li lon ci c2 4 82 5 Vin 80V 4 7uF VIN sw m 22r Y 2 104 2V AAT1239 1 ud ls 800 OVP Ta L y o d 4 PGND L E 2 775 7 E Nig tg Sgt Bi r t gt EN SET FB 1 ted ER 75 0 Vy 3 0V R1 gt SEL AGND 30 10 ES E 72 5 Vi 3 6V C1 10V 0805 X5R 4 7uF GRM219R61A475KE19 E 70 0 mm Vi sd C2 50V 1206 X7R 2 24F GRM31CR7 1H225KA88 L1 104H CDRH3D18 100NC 10 12 14 16 18 20 lour mA DS1 SS16L Figure 15 Enhanced Efficiency Configuration for Li ion Battery Ten WLEDs Series Connected Application
14. S a Ml x OVP i T x gt Enable Set gt ____ _ EN SET m x x Feedback Voltage SEL x Select gt H Y N o x FB Y y N PGND AGND N N keo 1 Ranas White LEDs T 20mA 30 1 y OSRAM LW M678 NX or equivalent N E x x 1239 1 2008 10 1 2 www analogictech com 1 PRODUCT DATASHEET Om ee AAT 1239 1 SwitchReg 40V Step Up Converter for 4 to 10 White LEDs D Pin Descriptions Pin Symbol Function PVIN Input power pin connected to the source of the P channel MOSFET Connect to the input capacitor s EN SET IC enable pin and S Cwire input control to set output current FB voltage range select A logic LOW sets the FB voltage range from 0 4V to 0 1V a logic HIGH sets the FB voltage range from 0 6V to 0 3V VIN Input voltage for the converter Connect directly to the PVIN pin N C No connection SW Boost converter switching node Connect the power inductor between this pin and LIN PGND Power ground for the boost converter AGND Ground pin FB Feedback pin Connect a resistor to ground to set the maximum LED current OVP Feedback pin for over voltage protection sense LIN Switched power input Connect the power inductor between this pin and SW SEL TSOPJW 12 Top View 2 www analogictech com 1239 1 2008 10 1 2 PRODUCT DATASHEET css AAT1239 I SwitchReg 40V Step Up Converter for 4 to 10 White LEDs Part Number Descript
15. T1239 1 the possible scaling factors are 3 0x to 1 5x with the internal default setting of 1 5x Default Select Pin Scaling Factor Low to High S Cwire Data Register Figure 6 AAT1239 1 SEL Pin Scaling Factor Tien SEL High Divided by Iiep SEL Low S Cwire Serial Interface AnalogicTech s S Cwire single wire serial interface is a proprietary high speed single wire interface available only from AnalogicTech The S Cwire interface records Ah Tio E That gt 40V Step Up Converter for 4 to 10 White LEDs rising edges of the EN SET input and decodes them into 16 individual states Each state corresponds to a refer ence feedback voltage setting on the FB pin as shown in Table 2 S Cwire Serial Interface Timing The S Cwire single wire serial interface data can be clocked in at speeds up to 1MHz After data has been submitted EN SET is held high to latch the data for a period Tiar The FB pin voltage is subsequently changed to the level as defined by the state of the SEL logic pin When EN SET is set low for a time greater than Tors the AAT1239 1 is disabled When the AAT1239 1 is disabled the register is reset to its default value In the AAT1239 1 the FB pin voltage is set to 0 3V if the EN SET pin is subsequently pulled HIGH S Cwire Feedback Voltage Programming The FB pin voltage is set to the default level at initial powerup The AAT1239 1 is program
16. This eliminates leakage current making the devic es ideally suited for battery powered applications The AAT1239 1 is available in the Pb free thermally enhanced 12 pin TSOPJW package Typical Application e Input Voltage Range 2 7V to 5 5V e Maximum Continuous Output 40V 30mA e Drives up to 10 LEDs in Series Constant LED Current with 3 5 Accuracy Over Temperature and Input Voltage Range e Digital Control with S Cwire Single Wire Interface 26 Discrete Steps No PWM Control Required No Additional Circuitry e Up to 85 Efficiency e Up to 2MHz Switching Frequency Allows Small External Chip Inductor and Capacitors e Hysteretic Control No External Compensation Components Excellent Load Transient Response High Efficiency at Light Loads e Integrated Soft Start with No External Capacitor e True Load Disconnect Guarantees lt 1 0uUA Shutdown Current e Selectable Feedback Voltage Ranges for High Resolution Control of Load Current e Short Circuit Over Voltage Protection e 12 Pin TSOPJW Package e 40 C to 85 C Temperature Range and Over Temperature Applications e Color Display Backlight e Digital Still Cameras DSCs e Digital Photo Frames e PDAs and Notebook PCs e White LED Drivers L1 DS1 2 20H SS16L or equivalent PVIN LIN AON pt c2 22yF Li lon os VIN Sw M673 o R2 Vin 2 7V to 4 2v T 77H 74k AAT1239 1 Y E
17. W 150 Q 100 o z z Lu ul 100 50 2 7 3 1 3 5 3 9 4 3 4 7 5 1 5 5 24 3 1 3 5 3 9 4 3 4 7 5 1 5 5 Input Voltage V Input Voltage V 1239 1 2008 10 1 2 www analogictech com 7 PRODUCT DATASHEET mao AAT1239 1 SwitchReg 40V Step Up Converter for 4 to 10 White LEDs Typical Characteristics Enable High Threshold Vn vs Input Voltage Enable Low Threshold V vs Input Voltage 1 2 1 1 1 0 LE 0 9 0 8 AAA 0 7 0 6 0 5 Enable High Threshold Vi V Enable Low Threshold V V 27 3 1 3 5 3 9 43 47 5 1 5 5 27 3 1 3 5 3 9 4 3 47 5 1 5 5 Input Voltage V Input Voltage V 8 www analogictech com 1239 1 2008 10 1 2 NALOGIC CA TECH PRODUCT DATASHEET AAT 1239 SwitchReg Functional Block Diagram 40V Step Up Converter for 4 to 10 White LEDs PVIN VIN EN SET FB Output Reference Select SEL Control AO LIN Functional Description The AAT1239 1 consists of a DC DC boost controller an integrated slew rate controlled input disconnect MOSFET switch and a high voltage MOSFET power switch A high voltage rectifier power inductor output capacitor and sense resistors are required to implement a DC DC con stant current boost converter The input disconnect switch is activated when a valid input v
18. Z5 ANALOGIC E TECH PRODUCT DATASHEET AAT 1239 SwitchReg General Description 40V Step Up Converter for 4 to 10 White LEDs Features The AAT1239 1 is a high frequency high efficiency con stant current boost converter capable of driving up to ten 10 series connected white LEDs or 40V It is an ideal power solutions for backlight applications with up to ten white LEDs in series The input voltage is 2 7V to 5 5V for single cell lithium ion polymer Li ion based portable devices The LED current is digitally controlled across a 6x oper ating range using AnalogicTech s Simple Serial Control S Cwire interface Programmability across 26 dis crete current steps provides high resolution low noise flicker free constant LED outputs In programming AAT1239 operation LED brightness increases based on the data applied at the EN SET pin The SEL logic pin changes the feedback voltage between two program mable ranges The AAT1239 1 features a high current limit and fast stable transitions for stepped or pulsed current applica tions The high switching frequency up to 2MHz pro vides fast response and allows the use of ultra small external components including chip inductors and capacitors Fully integrated control circuitry simplifies design and reduces total solution size The AAT1239 1 offers a true load disconnect feature which isolates the load from the power source while in the OFF or disabled state
19. age V Temperature C 1239 1 2008 10 1 2 www analogictech com 5 PRODUCT DATASHEET es AAT 1239 1 SwitchReg 40V Step Up Converter for 4 to 10 White LEDs D Typical Characteristics Soft Start Soft Start 10 White LEDs Veg 0 6V 10 White LEDs Veg 0 3V s z 3 z 9 o6 33V 3 m T 33V 5 m 3 o4 ov 83 3 uv Ss E o9 E o9 33 o 004 S 9 2 EZ g o 2 ES x A 9 9 x 9 9 o 123 o 123 o G o 3 o 332 3 0 32 o o d t 2 m Time 200us div Time 200us div Shutdown Shutdown 10 White LEDs V g 0 6V 10 LEDs V 0 3V _ 2 3 3 2 _ 2 3 3V 2 22 S 22 S 23 E 8 as oy S SE o SE o Sa 06 e OF E H d 2 S S 0 2 P44 S 02 E 0 E 2x 9 2x 9 a 0 05 20 05 GG MERE 9 GG 9 HE o0 3 52 ie o 3 o o i 2 Time 100us div Time 50us div Output Ripple Output Ripple 10 White LEDs Vn 3 6V Cour 2 2pF lLep 13mA 10 White LEDs Vn 3 6V Cour 2 2pF l gp 20mA Mo LLL LLLI 4 Vour AC Coupled AC Coupled 20mV div 20mV div ml MR JU Un JU VISA Vsw iy fal fl Vsw IL IL IL 20V div 20V div E FAA A ANA E 500mA div 500mA div Ti
20. ce for the AAT1239 1 boost converter The out put diode is sized to maintain acceptable efficiency and reasonable operating junction temperature under full load operating conditions Forward voltage V and package thermal resistance 054 are the dominant fac tors to consider in selecting a diode The diode non re petitive peak forward surge current rating Issm should be considered for high pulsed load applications such as camera flash Ies rating drops with increasing conduc tion period Manufacturers datasheets should be con sulted to verify reliability under peak loading conditions The diode s published current rating may not reflect actual operating conditions and should be used only as a comparative measure between similarly rated devices 40V rated Schottky diodes are recommended for outputs less than 30V while 60V rated Schottky diodes are rec ommended for outputs greater than 35V The switching period is divided between ON and OFF time intervals E Ton Torr During the ON time the N channel power MOSFET is conducting and storing energy in the boost inductor During the OFF time the N channel power MOSFET is not conducting Stored energy is transferred from the input battery and boost inductor to the output load through the output diode Duty cycle is defined as the ON time divided by the total switching interval Ton D tt Ton Torr Ton Fs AII table entries are preliminary and subject to
21. e switching frequency varies with output load and input voltage The value of the inductor determines the maxi mum switching frequency of the boost converter Increased output inductance decreases the switching fre quency and switching loss but results in higher peak currents and increased output voltage ripple To maintain 2MHz maximum switching frequency and stable opera tion an output inductor sized from 1 5uH to 2 7uH is recommended For higher efficiency in Li ion battery applications Vi from 3 0V to 4 2V and stable operation increasing the inductor size up to 10H is recommended Figure 15 and 16 show the special enhanced efficiency application A better estimate of Dmax is possible once Ve is known D Vour Ve Z Vin Tt Vour Ve Where V is the Schottky diode forward voltage If not known it can be estimated at 0 5V Manufacturer s specifications list both the inductor DC current rating which is a thermal limitation and peak inductor current rating which is determined by the satu ration characteristics Measurements at full load and high ambient temperature should be completed to ensure that the inductor does not saturate or exhibit excessive temperature rise Rated Thermal Voltage Resistance 93a C W Size mm LxWxH 3 8x1 9x1 43 Sub SMA Taiwan Semiconductor Co Ltd SS15L 3 8x1 9x1 43 Sub SMA SS14L 3 8x1 9x1 43 Sub SMA Diodes Inc B340LA 5 59x2 92x2 30 SM
22. he AAT1239 1 provides the benefits of current mode control with a simple hysteretic output current loop pro viding exceptional stability and fast response with mini mal design effort The device maintains exceptional constant current regulation transient response and cycle by cycle current limit without additional compen sation components The AAT1239 1 modulates the power MOSFET switching current to maintain the programmed FB voltage This allows the FB voltage loop to directly program the 1239 1 2008 10 1 2 www analogictech com 9 ANALOGIC E TECH AAT 1239 PRODUCT DATASHEET SwitchReg required inductor current in order to maintain the desired LED current The switching cycle initiates when the N channel MOSFET is turned ON and current ramps up in the inductor The ON interval is terminated when the inductor current reaches the programmed peak current level During the OFF interval the input current decays until the lower threshold or zero inductor current is reached The lower current is equal to the peak current minus a preset hys teresis threshold which determines the inductor ripple current The peak current is adjusted by the controller until the LED output current requirement is met The magnitude of the feedback error signal determines the average input current Therefore the AAT1239 1 controller implements a programmed current source connected to the output capacitor parallel with the LED
23. ion yields worst case inductor loss The RMS current value should Inductance Part Number HH CDRH2D14 2R2 Manufacturer Maximum DC Isat DCR Current mA mQ 40V Step Up Converter for 4 to 10 White LEDs be compared against the manufacturer s temperature rise or thermal derating guidelines legAK laus 7 43 For a given inductor type smaller inductor size leads to an increase in DCR winding resistance and in most cases increased thermal impedance Winding resistance degrades boost converter efficiency and increases the inductor s operating temperature PLoss InDUCTOR laus DCR To ensure high reliability the inductor case temperature should not exceed 100 C In some cases PCB heatsink ing applied to the LIN node non switching can improve the inductor s thermal capability PCB heatsinking may degrade EMI performance when applied to the SW node switching of the AAT1239 1 Shielded inductors provide decreased EMI and may be required in noise sensitive applications Unshielded chip inductors provide significant space savings at a reduced cost compared to shielded wound and gapped induc tors In general chip type inductors have increased winding resistance DCR when compared to shielded wound varieties Size mm LxWxH 3 2x3 2x1 55 Shielded Sumida CDRH2D14 4R7 3 2x3 2x1 55 Shielded www sumida com CDRH4D22 HP 4R7 5 0x5 0x2 4 Shielded CDRH3D18 100NC 4 0x4 0x2 0 Shielded
24. ions SEL Polarity Part Number HIGH LOW S C Feedback Voltage Programming AAT1239ITP 1 0 6V gt Vrs gt 0 3V 0 4V gt Vrs 2 0 1V See Table 2 Absolute Maximum Ratings Ta 25 C unless otherwise noted Description PVIN VIN Input Voltage 0 3 to 6 0 sw Switching Node 45 LIN EN SET SEL FB Maximum Rating Vin 0 3 T Operating Temperature Range 40 to 150 Ts Storage Temperature Range 65 to 150 Teno Maximum Soldering Temperature at leads 10 sec 300 Thermal Information Description Units Thermal Resistance C W Maximum Power Dissipation mW 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 1239 1 2008 10 1 2 www analogictech com 3 D Z ANALOGIC SwitchReg TECH Electrical Characteristics Ta 40 C to 85 C unless otherwise noted Typical values are at 25 C Vin 3 6V Symbol Power Supply PVin Vin Description Input Voltage Range Conditions Vour max Maximum Output Voltage lo Operating Current SEL GND FB 0 1V Ison Shutdown Current EN SET GND Tour Maximum Continuous Output Current 2 7V lt Vin lt 5 5V Vout 40V AV unenec re AViN Line Regulation Vin
25. is pulled high The slew rate control on the P channel MOSFET ensures minimal inrush current as the output voltage is charged to the input voltage prior to switching of the 40V Step Up Converter for 4 to 10 White LEDs N channel power MOSFET Monotonic turn on is guaran teed by the built in soft start circuitry Soft start elimi nates output current overshoot across the full input volt age range and all loading conditions After the soft start sequence has terminated the initial LED current is determined by the internal default FB voltage across the external ballast resistor at the FB pin Additionally the AAT1239 1 has been designed to offer the system designer two choices for the default FB volt age based on the state of the SEL pin Changing the LED current from its initial default setting is easy by using the S Cwire single wire serial interface the FB voltage can be decreased as in the AAT1239 1 see Table 2 relative to the default FB voltage Current Limit and Over Temperature Protection The switching of the N channel MOSFET terminates when a current limit of 2 5A typical is exceeded This mini mizes power dissipation and component stresses under overload and short circuit conditions Switching resumes when the current decays below the current limit Thermal protection disables the AAT1239 1 when inter nal dissipation becomes excessive Thermal protection disables both MOSFETs The junction over temperature th
26. me 200ns div Time 200ns div 6 www analogictech com 1239 1 2008 10 1 2 PRODUCT DATASHEET es AAT1239 SwitchReg 40V Step Up Converter for 4 to 10 White LEDs Typical Characteristics Transition of LED Current Transition of LED Current 10 White LEDs SEL Low lLep 3mA to 13mA 10 White LEDs SEL Low l p 13mA to 6mA S 34 S sn 3 7 3 d A z Ge Goa o 30 oc o 30 oc o ao o ao S 28 04 x S 04 Sx lt o lt 3s 0 3 E ia 3 H HHEENSEEH s 2 0 2 3 0 2 3 a 3 s 5 O O i 0 0 0 0 Time 50ps div Time 50ps div Input Disconnect Switch Resistance Low Side Switch On Resistance vs Input Voltage vs Input Voltage 300 260 280 240 260 120 C 220 120 C 20 100 C E 20 100 C 180 220 2 3 160 E g 200 A 140 85 C 85 C 180 25 C 120 Dn 160 100 25 C 140 80 l 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 47 Dal 5 5 Input Voltage V Input Voltage V EN SET Latch Timeout vs Input Voltage EN SET Off Timeout vs Input Voltage 350 300 2 T i E n 40 C 5 300 n 250 o 2 o 2 E EA 40 C 200 lt E 25 C 85 C 200 85 C 5 150 E 25 C m
27. med through the S2Cwire interface Table 2 illustrates FB pin voltage pro gramming for the AAT1239 1 The rising clock edges applied at the EN SET pin determine the FB pin voltage If a logic LOW is applied at the SEL pin of the AAT1239 1 the default feedback voltage range becomes 0 4V to 0 1V and 0 6V to 0 3V for a logic HIGH condition at the SEL pin EN SET 2 p gt ny RN zi CD n lt 16 o Data Reg NS Figure 7 AAT1239 1 S Cwire Timing Diagram to Program the Output Voltage 14 www analogictech com 1239 1 2008 10 1 2 ANALOGIC E TECH PRODUCT DATASHEET AAT 1239 SwitchReg SEL Low Rising Clock Edges Data Register Reference Voltage V 0 4 default LED Current mA Rsauast 30 10 40V Step Up Converter for 4 to 10 White LEDs SEL High LED Current mA Raauasr 30 10 Reference Voltage V 0 6 default 0 38 0 58 0 36 0 56 0 34 0 54 0 32 0 52 0 30 0 50 0 28 0 48 0 26 0 46 0 24 0 44 0 22 0 42 0 20 0 40 0 18 0 38 0 16 0 36 0 14 0 34 0 32 Table 2 AAT1239 1 S Cwire Reference Feedback Voltage Control Settings With Rgaiast 30 10 Assumes Nominal Values Selecting the Schottky Diode To ensure minimum forward voltage drop and no recov ery high voltage Schottky diodes are considered the best choi
28. mum LED current program ming error Alep is proportional to voltage error across an individual LED AVzgzgp N Veieperve Wour ovP_MIN Veg AVg gp To minimize the Al error the minimum OVP voltage Vourtove mi may be increased yielding a corresponding increase in the maximum OVP voltage Vour ove wa Measurements should confirm that the maximum switch ing node voltage Vswmax is less than 45V under worst case operating conditions R Vswiuax Vove max amp t 1 Ve Veo V Schottky Diode DS1 forward voltage at turn OFF Vai Voltage ring occurring at turn OFF LED Selection and Current Setting The AAT1239 1 is well suited for driving white LEDs with constant current Applications include main and sub LCD display backlighting and color LEDs The LED current is controlled by the FB voltage and the ballast resistor For maximum accuracy a 1 tolerance resistor is recommended The ballast resistor Rgauastr value can be calculated as follows Ves max Reattast l LED MAX 40V Step Up Converter for 4 to 10 White LEDs where Ves max 0 4V when SEL Low VeBcmax 0 6V when SEL High i e for a maximum LED current of 20mA SEL High Ve 06 Reattast ar 0 020 300 30 10 Maximum AS Current mA Reattast 9 SEL High SEL Low Table 1 Maximum LED Current and Reattast Resistor Values 1 Resistor Tolerance Typical whi
29. nect to the IC PGND pin s as well as the GND terminals of C1 and C2 Consider additional PCB area on DS1 cathode to maximize heatsinking capability This may be neces sary when using a diode with a high Ve and or ther mal resistance To avoid problems at startup add a 10kQ resistor between the VIN VP and EN SET pins R4 This is critical in applications requiring immunity from input noise during hot plug events e g when plugged into an active USB port of eil III III 2 SM AA E el P q e 19 e e e Ed ra oy geal E asa fo 00 090 no e eo 090 Figure 10 AAT1239 1 Evaluation Board Bottom Side Layout with ten LEDs and microcontroller 1239 1 2008 10 1 2 www analogictech com 19 PRODUCT DATASHEET M Om ee AAT 1239 1 SwitchReg 40V Step Up Converter for 4 to 10 White LEDs S Cwire Microcontroller U2 PIC12F675 R8 3300 Select D12 4 Red Down Up m J JP2 JP3 R4 10k AAT1239 1 DC DC L1 s eod White LED esp 10pH enone i AAA E VOUT Driver G S CC 4 AAT1239 1 15 R 10uF Se Y raped VIN LIN H 374k JP4 1123 EN OVP M yo EE 3 SEL FB 10 R3 E WLED 2ul 4 9 D2 ve GND 12k X wep Lao nc PGND L5 vot 4TyF SW SW y y y WLED as R A wto AAA eye Nid Nig 30 10 Di0 D9 D8 D7 Bw IL WLED WLED WLED WLED WLED Figure 11 AAT1239 1
30. oltage is present and the EN SET pin is pulled high The slew rate control on the P channel MOSFET ensures minimal inrush cur rent as the output voltage is charged to the input volt age prior to the switching of the N channel power MOSFET Monotonic turn on is guaranteed by the inte grated soft start circuitry Soft start eliminates output voltage overshoot across the full input voltage range and all loading conditions The maximum current through the LED string is set by the ballast resistor and the feedback voltage of the IC The output current may be programmed by adjusting the level of the feedback reference voltage which is pro grammed through the S Cwire interface The SEL pin selects one of two feedback voltage ranges In the AAT1239 1 the SEL function is inverted in that the FB pin voltage can be programmed from 0 4V to 0 1V with AGND PGND a logic LOW applied to the SEL pin and 0 6V to 0 3V with a logic HIGH applied to the SEL pin The feedback volt age can be set to any one of 16 current levels within each FB range providing high resolution control of the LED current using the single wire S Cwire control For some applications requiring a short duration of boosting current applying a low to high transition on the AAT1239 1 s SEL pin LED current can be programmed up to 3x The step size is determined by the programmed voltage at the FB pin where the internal default setting is 1 5x in the AAT1239 1 Control Loop T
31. ors of type X7R or X5R are Part Number GRM188R60J225KE19 Manufacturer Murata Value pF 40V Step Up Converter for 4 to 10 White LEDs recommended to ensure good capacitance stability over the full operating temperature range The output capacitor is sized to maintain the output load without significant voltage droop AVour during the power switch ON interval when the output diode is not conducting A ceramic output capacitor from 2 2uF to 4 7uF is recommended see Table 5 Typically 50V rated capacitors are required for the 40V maximum boost output Ceramic capacitors sized as small as 0805 or 1206 are available which meet these requirements MLC capacitors exhibit significant capacitance reduction with applied voltage Output ripple measurements should confirm that output voltage droop and operating stability are acceptable Voltage derating can minimize this fac tor but results may vary with package size and among specific manufacturers Output capacitor size can be estimated at a switching frequency Fs of 500kHz worst case To maintain stable operation at full load the output capacitor should be sized to maintain AVoyr between 100mV and 200mV The boost converter input current flows during both ON and OFF switching intervals The input ripple current is less than the output ripple and as a result less input capacitance is required Voltage Rating Temp Co Case Size Murata GRM188R61A225KE34 Murata
32. reshold is 140 C with 15 C of temperature hysteresis The output voltage automatically recovers when the over temperature fault condition is removed Over Voltage Protection Over voltage protection prevents damage to the AAT1239 1 during open circuit or high output voltage conditions An over voltage event is defined as a condi tion where the voltage on the OVP pin exceeds the over voltage threshold limit Voy 1 2V typical When the voltage on the OVP pin has reached the threshold limit the converter stops switching and the output voltage decays Switching resumes when the voltage on the OVP pin drops below the lower hysteresis limit main taining an average output voltage between the upper and lower OVP thresholds multiplied by the resistor divider scaling factor Under Voltage Lockout Internal bias of all circuits is controlled via the VIN input Under voltage lockout UVLO guarantees sufficient Vi bias and proper operation of all internal circuitry prior to soft start 10 www analogictech com 1239 1 2008 10 1 2 Z5 ANALOGIC E TECH PRODUCT DATASHEET AAT 1239 SwitchReg Application Information Over Voltage Protection OVP Protection with Open Circuit Failure The OVP protection circuit consists of a resistor network tied from the output voltage to the OVP pin see Figure 1 To protect the device from open circuit failure the resistor divider can be selected such that the over volt
33. ristics Vago quantity of series connected LEDs N and the feedback pin voltage Vrs Vour Veg N Veneno When the rising OVP threshold is exceeded switching is stopped and the output voltage decays Switching auto matically restarts when the output drops below the lower OVP hysteresis voltage 100mV typical and as a result the output voltage increases The cycle repeats maintaining an average DC output voltage proportional to the average of the rising and falling OVP levels mul tiplied by the resistor divider scaling factor High oper ating frequency and small output voltage ripple ensure DC current and negligible flicker in the LED string s The waveform in Figure 3 shows the output voltage and LED current at cold temperature with a ten series white LED string and Voy 40V As shown the output voltage rises as a result of the increased Veep which triggers the OVP constant voltage operation Self heating of the LEDs triggers a smooth transition back to constant cur rent control 1239 1 2008 10 1 2 www analogictech com 11 ANALOGIC E TECH AATI1239 1 PRODUCT DATASHEET H TM SwitchReg i ver Volgo Protection Cold Temperature Apply Self Recovery Vout 5V div leo a 200mA div a Gill 200mv ch2 3 00V M 1 00s Ch 7 200mV Figure 3 Over Voltage Protection Constant Voltage Operation 10 White LEDs Ieo 20mA R 12kQ R 374k0 While OVP is active the maxi
34. string and ballast resistor There is no right half plane zero and loop stability is achieved with no additional compensation components An increase in the feedback voltage Veg results in an increased error signal sensed across the ballast resistor R1 The controller responds by increasing the peak inductor current resulting in higher average current in the inductor and LED string s Alternatively when the Veg is reduced the controller responds by decreasing the peak inductor current resulting in lower average current in the inductor and LED string s Under light load conditions the inductor OFF interval current goes below zero and the boost converter enters discontinuous mode operation Further reduction in the load current results in a corresponding reduction in the switching frequency The AAT1239 1 provides pulsed frequency operation which reduces switching losses and maintains high efficiency under light load conditions Operating frequency varies with changes in the input volt age output voltage and inductor size Once the boost converter has reached continuous mode further increases in the LED current will not significantly change the operat ing frequency A small 2 20H 420 inductor is selected to maintain high frequency switching up to 2MHz and high efficiency operation for outputs up to 40V Soft Start Enable The input disconnect switch is activated when a valid input voltage is present and the EN SET pin
35. te LEDs are driven at maximum continuous currents of 15mA to 20mA The maximum number of series connected LEDs is determined by the minimum OVP voltage of the boost converter Vour ovr_mm minus the maximum feedback voltage Vrsmax divided by the maximum LED forward voltage Vrieo max Vriep max Can be estimated from the manufacturers datasheet at the maximum LED operating current R Vour ovP MIN Vovertyp amp 1 N Voutiove MIN 7 Wee max WeLED MAX Figure 4 shows the schematic of using ten LEDs in series Assume Vreo 20mA 3 5V typical from LW M673 OSRAM datasheet 374kQ Vourove uw 1 2V pe 1 38 6V y 38 6V 0 6V 35V 10 9 Therefore under these typical operating conditions ten LEDs can be used in series 12 www analogictech com 1239 1 2008 10 1 2 e PRODUCT DATASHEET ANAL AAT 1239 1 pz SwitchReg 40V Step Up Converter for 4 to 10 White LEDs DS1 L1 22uH f 1 e 6 e vy LED JP1 RA 10K U1 R2 7 1 ew 1 VIN LIN 2 2748 eo i a Q j cr 1 2 R3 2 24F T Enable s Hus EOS 1x ED 02 JP2 5 sw SW 9 2 24F 1 AAT1239 1 TSOP12JW 7 LED E 10 S 1 RI Z LED Select AWW 30 1 mm C1 10V 0603 X5R 2 20F GRM188R60J225KE01D C2 50V 1206 X7R 2 20uF GRM31CR71H225KA88 L1 2 20H SD3814 2R2 or SD311
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ANALOGICTECH AAT1239 1 40V Step Up Converter for 4 to 10 White LEDs handbook