austriamicrosystems AG is now ams AG The technical content of this austriamicrosystems datasheet is still valid. Contact information: Headquarters: ams AG Tobelbaderstrasse 30 8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 e-Mail: [email protected] Please visit our website at www.ams.com D atas he et A S3 8 3 3 1 General Description The integrated step-up controller provides the necessary output voltage for the LED string supply. The SMPS feedback control optimizes the power efficiency by adjusting the LED string supply voltage. 2 Key Features 6 channel LED controller Step-up controller optimized for 2D/3D mode Supply voltage range: 12V to 50V Figure 1. AS3833 Output current up to 250mA per channel Absolute current accuracy +/- 0.8% Channel to channel accuracy+/- 0.6% 1 PWM input with internal phase shift Open LED detection and disconnect Short LED protection and auto-turnoff Undervoltage shutdown Temperature shutdown Temperature supervision of external BJT BJT Beta compensation SMPS feedback control DCDC Softstart Function Over Voltage Protection (OVP) Package SOIC-28 Package TQFP-32 am lc s on A te G nt st il Build in safety features include under-voltage and thermal shutdown as well as open and short LED detection. lv The AS3833 is a 6 channel high precision LED controller with PWM input for driving external bipolar transistors in LCD-backlight panels, optimized for 2D and 3D operation. al id 6 c h a n n e l h ig h - p re c is io n L E D c o n tr o ll e r fo r 3 D- L C D b a ck l ig h t w it h in t eg ra t e d s te p - u p c o n t r o lle r 3 Applications Te ch ni ca LED backlighting for 3D-LCD backlight TV sets and monitors www.austriamicrosystems.com/AS3833 Revision 1.8 1 - 20 AS3833 Datasheet - C o n t e n t s Contents 1 General Description .................................................................................................................................................................. 1 2 Key Features ............................................................................................................................................................................ 1 3 Applications .............................................................................................................................................................................. 1 4 Pin Assignments (Top View) .................................................................................................................................................................................. 4 5 Absolute Maximum Ratings 6 Electrical Characteristics ...................................................................................................................................................... 5 .......................................................................................................................................................... 6 7 Typical Operating Characteristics ............................................................................................................................................. 8 ............................................................................................................................................................... 10 8.1 Precision current output ..................................................................................................................................................................... 10 lv 8 Detailed Description al id 4.1 Pin Descriptions ..................................................................................................................................................... 3 8.1.1 Phase shift .............................................................................................................................................................................. 10 8.2 VDDH_HC resistor ............................................................................................................................................................................. 11 8.3.1 8.3.2 8.3.3 8.3.4 ................................................................................................................................................................................... 11 Undervoltage lockout .............................................................................................................................................................. 11 Overtemperature Shutdown ................................................................................................................................................... 12 Short LED protection .............................................................................................................................................................. 12 Open LED detection ............................................................................................................................................................... 13 8.4 Boost controller 8.4.1 8.4.2 8.4.3 8.4.4 8.4.5 8.4.6 8.4.7 8.4.8 am lc s on A te G nt st il 8.3 Safety features .................................................................................................................................................................................. 13 Setting the output voltage ....................................................................................................................................................... 14 Continuous Conduction Mode (CCM) .................................................................................................................................... 15 Duty Cycle .............................................................................................................................................................................. 15 Inductor Current ..................................................................................................................................................................... 15 Input Capacitor ....................................................................................................................................................................... 16 Output Capacitor .................................................................................................................................................................... 16 Current Sense Resistor .......................................................................................................................................................... 16 Compensation Network .......................................................................................................................................................... 16 9 Package Drawings and Markings ............................................................................................................................................................. 20 Te ch ni ca 10 Ordering Information ........................................................................................................................................... 17 Revision 1.8 2 - 20 AS3833 Datasheet - P i n A s s i g n m e n t s ( To p V i e w ) 4 Pin Assignments (Top View) Te ch ni ca am lc s on A te G nt st il lv al id Figure 2. Pin Assignments (Top View) Revision 1.8 3 - 20 AS3833 Datasheet - P i n A s s i g n m e n t s ( To p V i e w ) 4.1 Pin Descriptions Pin Number AS3833 TQFP-32 Pin Number AS3833 SOIC-28 Pin Name Pin Type 29 1 VSS P 30 2 B4 A_I/O Base 4. Connect to base of external transistor. 31 3 E4 A_I/O Emitter 4. Connect to emitter of external transistor. 1 4 xFAULT DO_OD 2 5 ISET A_I/O Current setting. Connect current setting resistor. 3 6 UVLO A_I/O Undervoltage lockout input. 4 7 COMP A_I/O Compensation network. Connect compensation network. 5 8 6 9 7 10 8 11 10 12 11 13 12 14 14 am lc s on A te G nt st il Table 1. Pin Descriptions Description al id Analog Ground lv Fault output. Active low. Current sense input. Provide a short, direct PCB path between SENSE A_I/O FB A_I/O Output voltage feedback input. Input for voltage divider. Connect voltage divider output as short as possible to this pin VDDL A_I/O Voltage regulator output 3.3V. Connect 2.2µ F decoupling capacitor to GND GATE A_I/O Gate driver output. PGND P Power Ground VDDM P Voltage regulator output. Connect 2.2µ F decoupling capacitor to GND VDDH P Supply voltage. Connect 1µ F decoupling capacitor to GND 15 VDDH_HC P Voltage regulator Input. Connect 2.2µ F decoupling capacitor to GND 15 16 VTH A_I/O Reference input for overtemperature detection. 16 17 PWM1 DI_PD PWM input 1. PWM input for channel 1 17 18 E6 A_I/O Emitter 6. Connect to emitter of external transistor. 18 19 B6 A_I/O Base 6. Connect to base of external transistor. 19 20 B5 A_I/O Base 5. Connect to base of external transistor. 20 21 E5 A_I/O Emitter 5. Connect to emitter of external transistor. 21 22 VSS P 22 23 E2 A_I/O ni ca this pin and the positive side of the current sense resistor. Analog Ground Emitter 2. Connect to emitter of external transistor. 24 B2 A_I/O Base 2. Connect to base of external transistor. 25 B1 A_I/O Base 1. Connect to base of external transistor. 26 E1 A_I/O Emitter 1. Connect to emitter of external transistor. 26 27 E3 A_I/O Emitter 3. Connect to emitter of external transistor. 27 28 B3 A_I/O Base 3. Connect to base of external transistor. 23 24 Te ch 25 A_I/O...Analog pin, P...Power pin, DO...digital output, DO_OD...digital output open drain, DI...digital input, DI_PU...digital input with pullup resistor, DI_PD...digital input with pull down resistor Revision 1.8 4 - 20 AS3833 Datasheet - A b s o l u t e M a x i m u m R a t i n g s 5 Absolute Maximum Ratings Stresses beyond those listed in Table 2 may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Electrical Characteristics on page 6 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings Min Max Units Comments al id Parameter VDDH to VSS, VDDH_HC to VSS -0.3 55 V VDDM to VSS, GATE to VSS -0.3 25 V xFAULT to VSS -0.3 7 V VDDL to VSS -0.3 5 V 1 -0.3 5 V 2 -0.3 5 V Analog Pin Voltage to VSS am lc s on A te G nt st il Digital Pin Voltage to VSS Input Current (latch-up immunity) Electrostatic Discharge lv Electrical Parameters -100 100 mA Norm: JEDEC 78 Electrostatic Discharge HBM +/- 1500 V Norm: MIL 883 E method 3015 Electrostatic Discharge MM +/- 200 V Norm: JESD22-A115C Continuos Power Dissipation 1.5 W PT for SOIC-28 Package Continuos Power Dissipation Derating Factor 13 mW / °C PDERATE Junction to ambient thermal resistance 76 ºC/W SOIC-28 Package. For more information about thermal metrics, see application note AN01 Thermal Characteristics. Junction Temperature (TJmax) +150 ºC +150 ºC Continuos Power Dissipation (TA = +70°C) 3 4 Temperature Ranges and Storage Conditions Storage Temperature Range -55 ca Package Body Temperature ni Humidity non-condensing Moisture Sensitive Level 5 +260 ºC 85 % 1 The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/ JEDEC J-STD-020“Moisture/Reflow Sensitivity Classification for Non-Hermetic Solid State Surface Mount Devices”. The lead finish for Pb-free leaded packages is matte tin (100% Sn). Represents a max. floor life time of unlimited ch 1. Pins Vth, UVLO, Comp, Sense, FB, Iset, Ex, Bx Te 2. Pins PWMx 3. Depending on actual PCB layout and PCB used. 4. PDERATE derating factor changes the total continuous power dissipation (PT) if the ambient temperature is not 25ºC. Therefore for e.g. TA=85ºC calculate PT at 85ºC = PT - PDERATE x (85ºC - 25ºC) Revision 1.8 5 - 20 AS3833 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6 Electrical Characteristics VDDH = 24V, all voltages referenced to VSS, Typical values are at TA = +25°C (unless otherwise specified). All limits are guaranteed. The parameters with min. and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods. Table 3. Electrical Characteristics Symbol Parameter Conditions Min Typ Max Units TA Operating Temperature Range apply proper cooling to stay below maximum allowed TJ. -20 TJ Operating Junction Temperature -20 VDDH Supply Voltage +12 VDDM Driver supply voltage regulator output VDDL 3V voltage regulator output IDD Operating Current Consumption UVLO=2V, PWM1=0, Rset=6kΩ, Vth=0.47V 4.6 5.0 5.6 mA IDDQ Quiescent Current Consumption UVLO=0V, PWM1=0, Rset=6kΩ, Vth=0.47V 2.25 2.50 2.75 mA -0.8 +0.8 % al id General +115 °C +50 V +9 V +3.3 V am lc s on A te G nt st il Current sink parameters °C lv Power supply +85 ILED_100 Trimmed current accuracy ILED=100mA, Tj = 25°C excluding error of Rset ILED_ALL current accuracy ILED=50 to 250mA, BJT β>50 Tj = -20 to +115°C -1.5 +1.5 % ICH_100 Channel to channel accuracy ILED=100mA, Tj = 25°C -0.6 +0.6 % VIsetX Reference Voltage at pins Iset +1.22 V Ratio Ratio = ILED/Iset IBX Base output current limit 5.5 7.5 mA -10 +10 mV 1 +1.18 +1.20 500 Short detection comparator ACCshort Over-Temperature protection accuracy ca Power supply regulation Accuracy of Vbe comparison with VTH level BJT beta threshold Bth 45 48 52 Oscillator frequency 220 250 280 kHz Maximum duty cycle 85 87 89 % +1.23 +1.25 +1.27 V fosc ni Boost controller oscillator Boost controller PWM ch DMAX Boost controller error amplifier Reference Voltage at pin FB AV Voltage gain BW Bandwidth IFB_in Icomp_out Te VFB 80 dB AV = 0dB 2 MHz Voltage sense input current pins FB 0.1 Compensation output current pins COMP, Vcomp = 1V 10 0.2 µA µA Boost controller over current protection VSENSE Current sense threshold pin SENSE Revision 1.8 +600 +800 +1000 mV 6 - 20 AS3833 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s Table 3. Electrical Characteristics (Continued) Symbol Parameter Conditions Min Typ Max Units Rdriver Driver resistance sink and source pin GATE 4 6 8 Ω Vdriver GATE maximum output voltage IGATE = 0mA tRISE_driver GATE voltage rise time VGATE = 0 to 3V, CLOAD = 3nF 15 25 tFALL_driver GATE voltage fall time VGATE = 3 to 0V, CLOAD = 3nF 15 25 +1.28 +1.35 Boost controller driver VDDM Under voltage lockout threshold IUVLO_Hyst Under voltage lockout hysteresis current 20 Digital pins ns 50 ns +1.42 V µA lv VUVLO 50 al id Boost controller under voltage lockout V VIH Logic high input threshold VIL Logic low input threshold VOL Logic low output level RPU Input resistance Pull-up inputs 300 kΩ RPD Input resistance Pull-down inputs 300 kΩ V +0.8 V +0.3 V am lc s on A te G nt st il Thermal protection +1.8 PIN xFAULT open drain. I = -2mA TOFF Thermal shutdown threshold 140 °C Thyst Thermal shutdown hysteresis 30 °C Te ch ni ca 1. Is is not recommended to set ILED < 50mA in order to minimize influences of offset voltages. Revision 1.8 7 - 20 AS3833 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s 7 Typical Operating Characteristics VOUT Boost = 60V; IOUT = 1A, TAMB = +25ºC (unless otherwise specified). 100 90 90 80 80 70 70 60 50 40 60 50 40 30 30 20 20 10 10 lv Efficiency (%) 100 al id Figure 4. Boost - Efficiency vs. Output Current; VIN = 24V am lc s on A te G nt st il Efficiency (%) Figure 3. Boost - Efficiency vs. Output Current; VIN = 13V 0 0 0,1 1 10 0,1 1 10 Output Current (A) Output Current (A) Figure 5. VOUT vs. IOUT ,VIN = 13V 100 90 Output Voltage (V) 80 70 60 50 40 30 20 0 0 0,5 ca 10 1 1,5 2 2,5 3 3,5 4 Te ch ni Output Current (A) Revision 1.8 8 - 20 AS3833 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s Figure 6. VOUT vs. IOUT ,VIN = 24V 100 90 70 60 50 al id Output Voltage (V) 80 40 30 20 lv 10 0 0 0,5 1 1,5 2 2,5 3 3,5 4 am lc s on A te G nt st il Output Current (A) Figure 7. Boost - Efficiency vs. Input Voltage, IOUT = 1A 100 90 Efficiency (%) 80 70 60 50 40 30 20 10 0 10 12 14 16 18 20 22 24 26 28 30 Input Voltage (V) ca Figure 8. VOUT vs. Temp ,VIN = 24V, IOUT = 0.2A 100 70 60 ch Output Voltage (V) 80 ni 90 50 40 Te 30 20 10 0 -30 -15 0 15 30 45 60 75 90 Temperature (°C) Revision 1.8 9 - 20 AS3833 Datasheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description 8.1 Precision current output am lc s on A te G nt st il lv al id Figure 9. Current output stage The LED-current is derived from either Rset using the following equation Vset 1.2V I LED = RATIO × I set = RATIO × --------- = 500 × -----------Rset R SET (EQ 1) Iset is protected against a short to ground. In the case of a ground short the current Iset is limited to 660uA and the LED-current to 330mA. 8.1.1 Phase shift ca Iset has a lower limit of 6uA with a 1uA hysteresis.This sets the lower limit of the LED-current to 3mA with Rset=200kΩ. If Rset is large than 200kΩ, the LED-current is set to 0mA. ni The outputs are controlled by the PWM-input and a built in phase shift generator. All outputs are phase shifted by 1/6 of the PWM-period. In order to calculate the phase shift timing, two PWM-periods are needed. This means that after changing the PWM-frequency, the phase shift is updated after the second period. The PWM-frequency must be in the range from 60Hz to 1kHz. Te ch Figure 10. Phase shift Revision 1.8 10 - 20 AS3833 Datasheet 8.2 VDDH_HC resistor al id Figure 11. VDDH_HC resistor am lc s on A te G nt st il V in – 5V R VDDH_HC = ------------------75mA lv Pin VDDH_HC is connected to an internal 3.3V voltage regulator. In order to keep the power dissipation of this regulator low, it is recommended to connect pin VDDH_HC to the power supply Vin with a resistor. The resistor should guarantee sufficient voltage drop so that the remaining voltage at pin VDDH_HC is approximately 5V. The power dissipation of the RVDDH_HC hat to be considered. 2 P R VDDH_HC = ( 75mA ) × R VDDH_HC (EQ 2) (EQ 3) Typical values for RVVDH2 are: VIN = 13V: RVDDH_HC= 100Ω / 1W VIN = 24V: RVDDH_HC= 250Ω / 2W 8.3 Safety features 8.3.1 Undervoltage lockout ca In order to avoid startup of the Boost controller at low supply voltage an undervoltage lockout function is implemented. The boost controller only turns on when the voltage at pin UVLO exceeds VUVLO. Once the boost controller is turned on a current source IUVLO_Hyst is activated which increases the UVLO voltage and so shifts the turn off voltage level. Te ch ni Figure 12. Undervoltage lockout www.austriamicrosystems.com/AS3833 Revision 1.8 11 - 20 AS3833 Datasheet - D e t a i l e d D e s c r i p t i o n Following equations can be derived for adjusting the threshold voltages: Undervoltage lockout LOW level: 8.3.2 RUVLO1 V DDH_UVH = V UVLO × 1 + ------------------- RUVLO2 (EQ 4) R UVLO1 VDDH_UVL = VUVLO × 1 + ------------------- – I UVLO × R UVLO1 R UVLO2 (EQ 5) al id Undervoltage lockout HIGH level: Overtemperature Shutdown If the device temperature reaches TOFF the boost controller and all current outputs are turned off. After the temperature has decreased by Thyst all blocks are turned on again. Short LED protection lv 8.3.3 am lc s on A te G nt st il Figure 13. Short Led protection A built in short protection comparator is monitoring the junction temperature TJ of the external bipolar transistors by measuring the base-emitter voltage VBE. V BE = 1,2V – 0.002 × T J Tj....junction temperature in K (EQ 6) Te ch ni ca When the measured VBE gets lower than the voltage applied at pin Vth an overtemperature an hence an short LED condition is detected. Subsequently the fault output is activated (xFAULT = 0) and the corresponding output is deactivated. Revision 1.8 12 - 20 AS3833 Datasheet - D e t a i l e d D e s c r i p t i o n 8.3.4 Open LED detection am lc s on A te G nt st il lv al id Figure 14. Open Led detection A broken LED-string is detected during PWM=1. If a LED-string is broken the power supply feedback will increment the IDAC to increase the power supply output voltage. After the IDAC has reached its maximum value, a debounce counter is started. In order to run the debounce counter, the corresponding PWM-signal has to be high for more than 150us. After the debounce counter has counted up for 32ms, the fault output is activated (xFAULT = 0) and the corresponding output is disconnected from the power supply feedback loop. 8.4 Boost controller Te ch ni ca Figure 15. Boost controller Revision 1.8 13 - 20 AS3833 Datasheet - D e t a i l e d D e s c r i p t i o n 8.4.1 Setting the output voltage lv al id Figure 16. Vout setting According to the requirements of the LED strings, the output voltage Vout is adjusted by the internal power supply feedback Rfb1 V OUTmax = V fb 1 + ---------- + 255µA ⋅ R fb1 Rfb2 am lc s on A te G nt st il between: Rfb 1 V OUTmin = V fb 1 + ---------- Rfb 2 and Once Vout_min and Vout_max is known the external resistors can be caluclated: ( V OUTmax – V OUTmin ) (EQ 7) Rfb1 = ------------------------------------------------------255µA V fb R fb1 Rfb2 = ---------------------------------------( VOUTmin – V fb ) (EQ 8) Te ch ni ca Note: The overall resistance should be in the range of 100kΩ to 200kΩ to avoid any noise issues. Keep FB-line as short as possible. Revision 1.8 14 - 20 AS3833 Datasheet - D e t a i l e d D e s c r i p t i o n 8.4.2 Continuous Conduction Mode (CCM) For normal operation the converter should stay in continuous conduction mode, to ensure that the inductor value must be bigger than LCRIT. al id Where: VIN ... Input voltage at VDDH VOUT ... Output voltage VD ... Diode forward voltage at D1 fSW ... Switching frequency R ... Load resistor, should be calculated with minimum current load R = VOUT / IOUT_min Duty Cycle am lc s on A te G nt st il IOUT_min ... Minimum output current (e.g. for LED driver only one LED string is on) 8.4.3 (EQ 9) lv L CRIT V IN 1 – -------------------------- × V 2 IN × R V OUT + VD = --------------------------------------------------------------------2 2 × f SW × ( V OUT + VD ) Within CCM, the well known relation between input and output voltage is deriped in the following equation: this means for the duty cycle: 8.4.4 Inductor Current V OUT + VD 1 -------------------------- = ------------V IN 1–D (EQ 10) V IN D = 1 – --------------------------V OUT + VD (EQ 11) The inductor current varies during a switching cycle. This variation can be expressed by the mean value of the inductor current and the delta rise/ fall current within each cycle (see Figure 17). ch ni ca Figure 17. Inductor Current Te Mean inductor current: I OUT I L = ------------1–D (EQ 12) D × V IN ∆I L = ------------------fS × L (EQ 13) Delta inductor current: Revision 1.8 15 - 20 AS3833 Datasheet - D e t a i l e d D e s c r i p t i o n Peak current: ∆I L IOUT D × VIN I pk = IL + -------- = ------------- + ----------------------2 1 – D 2 × fS × L (EQ 14) RMS inductor current: 2 2 1 I L + ------ × ∆I L 12 (EQ 15) al id I RMS = Note: The saturation current of the inductor should be about 20 to 30% larger than the peak current 8.4.5 Input Capacitor 8.4.6 Output Capacitor am lc s on A te G nt st il The input capacitor has to supply the delta inductor current and it should be selected according to: lv This peak current is flowing through MN1 during phase 1 and through D1 during phase 2 of each cycle. Therefore this peak current is important for a proper diode , MOSFET and inductor selection. ∆I L C IN > -----------------------------------4 × ∆VIN × f SW (EQ 16) ∆VIN ESR < ----------------2 × ∆I L (EQ 17) The output capacitor must be chosen according to the max allowable output ripple at high load. I OUT – max × D C OUT > -----------------------------------∆VOUT × f SW 8.4.7 ca ∆V OUT ESR < ----------------------------------------------------I V IN × D OUT ------------ + ------------------------- 1 – D 2 × L × f SW (EQ 18) (EQ 19) Current Sense Resistor ch ni VSENSE R S – max = ----------------------------------I L + 0 , 5 × ∆I L P RS = I 2 L – rms × (EQ 20) RS × D (EQ 21) Note: Low inductance, specific designed current sensing resistors should be used, e.g. Stackpole Electronics CSR/CSRN series of sensing resistors with less than 0.2nH (typ.). Compensation Network Te 8.4.8 A typical choice for values of the compensation network is C10 = 100pF, C11 = 10nF, R11 = 100KΩ. Use these values as initial choice and evaluate the transient response of the system to verify the behavior at output load change. Revision 1.8 16 - 20 AS3833 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s 9 Package Drawings and Markings lv al id Figure 18. TQFP-32 Marking YY am lc s on A te G nt st il Table 4. Packaging Code last two digits of the current year WW G ZZ manufacturing week plant identifier free choice / traceability code WW R ZZ manufacturing week plant identifier free choice / traceability code Table 5. Packaging Code YY ca Figure 19. SOIC-28 Marking Te ch ni last two digits of the current year Revision 1.8 17 - 20 AS3833 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s Te ch ni ca am lc s on A te G nt st il lv al id Figure 20. TQFP-32 Package Revision 1.8 18 - 20 AS3833 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s Te ch ni ca am lc s on A te G nt st il lv al id Figure 21. SOIC-28 Package Revision 1.8 19 - 20 AS3833 Datasheet - O r d e r i n g I n f o r m a t i o n 10 Ordering Information The devices are available as the standard products shown in Table 6. Table 6. Ordering Information AS3833-ZTQT AS3833-ZSOT Description Delivery Form Package AS3833 Tape & Reel TQFP-32 AS3833 Tape & Reel SOIC-28 Note: All products are RoHS compliant and austriamicrosystems green. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect Technical Support is available at http://www.austriamicrosystems.com/Technical-Support Te ch ni ca am lc s on A te G nt st il For further information and requests, please contact us mailto: [email protected] or find your local distributor at http://www.austriamicrosystems.com/distributor al id Marking lv Ordering Code Revision 1.8 20 - 20