ELM916DA 450V LED controller ■General description ELM916DA is high efficiency LED driver control IC, which uses fewer components and drives LED with constant current. ELM916DA works in open loop and current mode, and can be programmed to operate in either constant frequency or constant off-time mode. ELM916DA consists of an 8 to 450V linear regulator, which makes working in wide input voltage range without external low voltage power supply. Internal 0 to 100% PWM dimming and 0 to 245mV linear dimming help to adjust LED luminance. ELM916DA is suitable for buck LED drivers; it is capable of providing good stability response because of open loop current mode control and with the controller, it is able to regulate output current without any compensation outstandingly. ■Features ■Application • • • • • • • • • • • • • • Open loop peak current controller Constant Current LED Driver LED string from one to hundreds of diodes Support linear and PWM dimming interface Requires few external components Buck system efficiency : >90% Internal linear regulator : 8 to 450V Constant off time function : 50% (when duty cycle is over) • Package : SOP-8 DC/DC LED driver applications RGB backlighting LED driver General purpose constant current source Signage and decorative LED lighting Chargers Non-isolation LED bulb ■Maximum absolute ratings Parameter VIN voltage power supply VDD voltage LD voltage PWMD voltage GATE voltage CS voltage RT voltage Power dissipation Operating ambient temperature Storage temperature Symbol Vin Vdd Vld Vpwmd Vgate Vcs Vrt Pd Top Tstg Limit 500 Unit V 36 V 7 V 630 -40 to +85 -55 to +150 mW °C °C Caution: Permanent damage to the device may occur when ratings above maximum absolute ones are used. ■Selection guide ELM916DA-N Symbol a b c Package Product version Taping direction D: SOP-8 A N: Refer to PKG file ELM916 D A - N ↑ ↑ ↑ a b c * Taping direction is one way. 6- 1 Rev.1.4 ELM916DA 450V LED controller ■Pin configuration SOP-8(TOP VIEW) 1 8 2 7 3 6 4 5 Pin No. 1 2 3 4 5 6 7 Pin name VIN CS GND GATE PWMD VDD LD 8 RT Pin description Input voltage 8 to 450V DC Sense LED string current Device ground Drives the gate of the external MOSFET Low frequency PWM dimming pin. Internally regulated supply voltage. Linear dimming input Frequency is controlled by external resistor. It can work with constant off time control when resistor connect to GATE ■Marking SOP-8 Mark ELM916DA Content Product name abc Assembly lot No.: 000 to 999 repeated ■Standard circuit Vin C1 R2 8 7 6 C2 5 RT VIN ELM916DA LD VDD CS GND PWMD GATE SBD R1 * 1 LED1 LED2 L 2 R4 * 3 C3 * 4 R3 * Option R1 for ESD. Option C3,R4 for blanking time. 6- 2 Rev.1.4 ELM916DA 450V LED controller ■Block diagram VIN 1 5V 7.5V HV Regulator LDO ● OSC 8 RT VDD 6 245mV + S Q LD 7 ● 4 GATE Driver R + 2 CS TST 3 5 GND PWMD ■Electrical characteristics Parameter Symbol Test condition Input DC supply voltage range Vindc Line voltage or DC input voltage Shut-down mode Iinsd PWM_D=GND, Vin=8V supply current Internal regulated voltage Vdd Vin=8 to 450V VDD under voltage lockout UVLO Vin rising threshold UVLO hysteresis ΔUVLO Vin falling PWMD input high level Ven(hi) Vin=8 to 450V PWMD input low level Ven(lo) Vin=8 to 450V Current sense pull-in Vcs-th Vin=8 to 450V, Top=25°C threshold voltage Linear dimming pin Vld Vin=8 to 450V voltage range Top=25°C, Vld=Vdd, Current sense blanking time Tblank Vcs=Vcs-th+50mV after Tblank Rosc=1MΩ Oscillator frequency Fosc Rosc=226kΩ Maximum duty cycle Dmax Vcs=0V, Vin=Open, Vdd=10V GATE sourcing current Isource Vgate=0V, Vdd=7.5V GATE sinking current Isink Vgate=Vdd, Vdd=7.5V GATE rising time tr Cgate=500pF, Vdd=7.5V GATE falling time tf Cgate=500pF, Vdd=7.5V Thermal shutdown Tsd temperature Thermal shutdown hysteresis Tsh 6- 3 Min. 8 Typ. Top=25°C Max. Unit 450 V 0.1 0.2 mA 6.7 7.5 8.0 V 5.5 6.0 6.5 V 0.8 mV V V 255 mV 250 mV 650 ns 2.0 235 500 245 0 250 500 65 20 83 165 165 50 50 95 95 150 150 kHz kHz % mA mA ns ns 155 °C 40 °C Rev.1.4 ELM916DA 450V LED controller ■Application notes ELM916DA, buck, boost or buck-boost converter controller with low cost, is specifically designed for driving multiple LED strings or arrays. It can be operated from either universal 90 to 240Vac or DC voltage between 8 and 450Vdc. ELM916DA is able to drive multiple strings of High-Brightness (HB) LEDs and regulate constant current to ensure brightness and spectrum of the LEDs. With constant current driving method, LED lifetime can be lengthened. ELM916DA provides soft start function to reduce inrush current. It is possible to charge LD capacitor by letting current of 1 to 5uA to flow to the resistor between VDD and LD. The voltage increases slopingly until it rises the current limit level of CS. By setting suitable resistor in CS, ELM916DA, with feedforward control, is capable of providing constant current to LED series while input voltage varies. It is possible that while ELM916DA is providing power supply to the internal circuit which consists of high voltage regulator for generating fixed VDD, ELM916DA is able to serve as a bias supply for low voltage external circuit. 1. LED driver operation ELM916DA can operate as basic types of converter controller under dis/continuous non-isolated current mode. When external power N-Mosfet is turned on by GATE, the input energy would be stored in the inductor through LED driver. When N-Mosfet is switched off, the energy stored in the inductor would be discharged toward LED. The internal power supply activates when voltage of VDD exceeds UVLO threshold. The output current is controlled current of CS. The current limit level of ELM196DA is set by LD. To avoid unstable regulation while ELM916DA is adopted in Buck topology, it is required to keep duty ratio under 50%; the input voltage is required to be designed as 2 times higher than the forward voltage of LEDs. 2. Supply current The current consumption under operation of ELM916DA is 0.2mA which can be generated from the internal HV circuit. For ELM916DA, it is not required to use bulky startup resistors which are typically necessary for offline applications. Moreover, since the internal regulator supplies 7.5V, it is possible that ELM916DA is able to supply the power continuously. Because the current consumption of ELM916DA is extremely low, the power consumption can be kept low even if the input voltage of ELM916DA is high. 3. Current detection The current detection input of ELM916DA is connected to non-inverting inputs of two comparators; inverting terminal of one comparator is connected to internal 245mV reference while it is connected to LD of the other one. Outputs of both comparators are connected to OR gate while output of OR gate is connected to reset pin of the flip-flop. Hence, the comparator whose voltage at inverting terminal is lower controlls when GATE output is turned off. The outputs of the comparators also include a 500ns blanking time due to the turn on spike current. Some solution will add RC filter to prevent this situation. 4. Dimming There are two types of dimming function of ELM916DA; linear and PWM types: 1) Linear dimming The linear dimming function of ELM916DA can be adjusted voltage level of LD by changing current limit. 6- 4 Rev.1.4 ELM916DA 450V LED controller 2) PWM dimming PWM dimming function of ELM196DA can be adjusted by driving PWMD with low frequency square wave . GATE drive output is zero when PWM signal is low; GATE drive output voltage is produced when PWMD is high. 5. Operating frequency The oscillator frequency of ELM916DA is set by RT external resistor. The following chart shows the connection between RT and frequency. f(Hz) 100k 20k 0 0 200k 1M Ω 6. Inductor selection The coil value can be calculated from the peak of ripple current of the required coil; please refer to the following formulas. Since ripple current is usually set to be 30% of LED drive current, the following example is shown based on 30% and the average LED drive current, ILED, is 350mA. The next step would be to determine total forward voltage of LED. If 10 HB LEDs are in series connection and the forward voltage of average current is set to be 3V, the total voltage descend of LEDs ,VLEDS, would be 30V. The input voltage from average synchorous circuit is: Vin=120V×1.414=170V The switching duty ratio is: D = Vleds/Vin = 30/170 = 0.176 If the given switching frequency is 50kHz, required ON time of MOSFET transistor would be: Ton = D/fosc = 3.52μs The required inductance of coil wouild be: (Vin - Vled)/L × Ton = 30% × Iled L = (Vin - Vled) × Ton/(0.3 × Iled) = 4.69mH 7. Input bulk capacitor An input filter capacitor should be designed to hold the rectified AC voltage above twice the LED string voltage throughout the AC line cycle. Assuming 15% relative voltage ripple across the capacitor, a simplified formula for the minimum value of the bulk input capacitor is given by: Cmin = Iled × 0.06 × Vled/V2in = 22μF 6- 5 Rev.1.4 ELM916DA 450V LED controller ■Buck topology sample application characteristics VIN C1 10μF R2 390kΩ SBD LED2 8 6 5 RT VIN ELM916DA LD VDD CS GND PWMD GATE 1 2 R4 470Ω 3 4 L 2mH C3 1nF R3 0.6Ω Vin-Average Iin Vin-Average Iled 400 70 390 Average Iled (mA) 60 Iin (mA) 50 40 30 20 10 0 3.5V, 350mAx3 LED3 7 C2 2.2μF LED1 R1 1kΩ 380 370 360 350 340 330 320 310 70 80 300 90 100 110 120 130 140 150 70 80 90 100 110 120 130 140 150 Vin (V) Vin (V) Vin-Fsw 60.00 58.00 Fsw (kHz) 56.00 54.00 52.00 50.00 48.00 46.00 44.00 42.00 40.00 70 80 90 100 110 120 130 140 150 Vin (V) 6- 6 Rev.1.4