January 10th, 2012 IRS2980S LED DRIVER CONTROL IC Product Summary IC Features • • • • • • • • Dimming LED driver controller Hysteretic Current Regulation Closed-loop LED current dimming control Analog/PWM Dimming Input Internal High Voltage Regulator Internal 15.6V zener clamp diode on Vcc Micropower startup (250μA) Latch immunity and ESD protection • • • Buck VOFFSET (breakdown) 600 V VOUT VCC IO+ & IO- (typical) 180mA & 260mA Package Types LED Driver System Features • • • Topology Single chip dimming solution Simple LED current dimming control method No external protection circuits required (fully internal) Low external component count Easy to use for fast design cycle time Increased manufacturability and reliability SO8 Typical applications • • LED incandescent/CFL replacement lamps LED driver module Typical Connection Diagram IRS2980 www.irf.com © 2011 International Rectifier 1 IRS2980S Table of Contents Page Description 3 Block Diagram 3 Qualification Information 4 Absolute Maximum Ratings 5 Recommended Operating Conditions 6 Electrical Characteristics 7 Input/Output Pin Equivalent Circuit Diagram 9 Lead Definitions 10 Lead Assignments 10 Application Information and Additional Details 11 Package Details 15 Tape and Reel Details 16 Part Marking Information 17 Ordering Information 18 www.irf.com © 2011 International Rectifier 2 IRS2980S Description The IRS2980S utilizes International Rectifier's control and high-voltage technologies to realize a simple, high-performance Buck LED driver solution. This solution is based on hysteretic output current regulation typically operating from 25 kHz to 120 kHz. Frequency and duty cycle vary to maintain a tightly regulated average output current over variations in line and load. Output current ripple will depend on inductor selection in conjunction with input and output voltages as well as output current and component selection. The IRS2980S uses a unique floating high side differential current sense and level shift scheme allowing hysteretic operation with a low side switching MOSFET optimizing size and cost. In addition, the IRS2980S includes a high voltage regulator able to operate up to 450V eliminating the need for an external VCC supply. A PWM dimming interface is also included that can be controlled from a 0 to 2V analog or 3.3 or 5V logic control signal able to operate up to 1kHz offering brightness control from 0 to 100%. A programmable on board PWM oscillator is used with DC dimming control. Block Diagram HV 1 5 ADIM 6 RAMP 7 OUT 4 COM 0.5V VCC Ref CS 8 2V 0.2V 15.6V VS 2 High Side Well 1V REGULATOR UVLO VCC VCC 3 NOISE FILTER + MAXIMUM FREQUENCY TIMING 15.6V www.irf.com © 2011 International Rectifier 3 IRS2980S † Qualification Information Qualification Level Moisture Sensitivity Level Machine Model ESD Human Body Model IC Latch-Up Test RoHS Compliant Industrial†† Comments: This family of ICs has passed JEDEC’s Industrial qualification. IR’s Consumer qualification level is granted by extension of the higher Industrial level. MSL2††† (per IPC/JEDEC J-STD-020C) Class B (per JEDEC standard JESD22-A115) Class 2 (per EIA/JEDEC standard EIA/JESD22-A114) Class I, Level A (per JESD78) Yes † †† Qualification standards can be found at International Rectifier’s web site http://www.irf.com/ Higher qualification ratings may be available should the user have such requirements. Please contact your International Rectifier sales representative for further information. ††† Higher MSL ratings may be available for the specific package types listed here. Please contact your International Rectifier sales representative for further information. www.irf.com © 2011 International Rectifier 4 IRS2980S Absolute Maximum Ratings Absolute Maximum Ratings indicate sustained limits beyond which damage to the device may occur. All voltage parameters are absolute voltages referenced to COM; all currents are defined positive into any lead. The Thermal Resistance and Power Dissipation ratings are measured under board mounted and still air conditions. Symbol Definition † Min. Max. Units VHV High Voltage Input -0.3 450 VOUT Low-Side Output Voltage -0.3 VCC + 0.3 VADIM VRAMP DIM Input Voltage -0.3 RAMP Input Voltage -0.3 VCC + 0.3 VCC + 0.3 --- 20 -500 500 --- 0.625 W ºC/W †† ICC PD Supply Current Maximum allowable current at OUT due to external power transistor Miller effect. ††† Maximum Power Dissipation @ TA ≤ +25ºC RθJA Thermal Resistance, Junction to Ambient --- 128 TJ Junction Temperature -55 150 TS Storage Temperature -55 150 TL Lead Temperature (Soldering, 10 seconds) --- 300 IOMAX V mA ºC † The IRS2980S uses an HVIC process capable of withstanding up to 600V, however the internal regulator maximum input voltage rating is limited to 450V maximum due to package power dissipation. The device can withstand transient voltages up to 600V for short periods. †† This IC contains a zener clamp structure between the chip VCC and COM which has a nominal breakdown voltage of 15.6V. This supply pin should not be driven by a DC, low impedance power source greater than the VCLAMP specified in the Electrical Characteristics section. ††† Power dissipation is dependent on VHV and switching frequency. In order to limit device temperature rise some thermal relief may be required in the form of copper on the PCB located under and around the device. Alternatively a small heat sink may be attached to the top of the device. Thermally conductive potting compounds can also provide excellent heat transfer. www.irf.com © 2011 International Rectifier 5 IRS2980S Recommended Operating Conditions For proper operation the device should be used within the recommended conditions. Symbol † Definition † Min. Max. Units VHV VCC ICC High Voltage Input Supply Voltage Supply Current 0 10.0 --- 375 VCLAMP 5 mA VRAMP VENN Pin Voltage 0 6 V VADIM VENN Pin Voltage 0 6 V VENN VENN Pin Voltage 0 6 V TJ Junction Temperature -40 125 ºC V Operation above this voltage level and below 450V is possible with sufficient heat sinking. www.irf.com © 2011 International Rectifier 6 IRS2980S Electrical Characteristics VHV=100V, VCC=14V, CVCC=0.1μF, CHVS=22nF, and TA = 25°C unless otherwise specified. The output voltage and current (VO and IO) parameters are referenced to COM and are applicable to OUT. Symbol Definition Min Typ Max Units Test Conditions 14.6 15.6 16.6 V ICC = 10mA --- 250 --- µA VCC = 6V Low Voltage Supply Characteristics VCLAMP VCC Zener Clamp Voltage IQCCUV Micropower Startup VCC Supply Current High Voltage Regulator Characteristics VCCREG VCC Regulation Voltage 8.9 9.9 10.9 V ICC = 1mA IREG_MAX Maximum Regulator Current --- 3 5 mA Vcc = 0V Minimum HV required for regulator† --- 60 --- V VHVMIN High Side Voltage Supply Characteristics VHVS+ High Side UVLO Positive Threshold 8.3 9.3 10.3 VHVS- High Side UVLO Negative Threshold 6.3 7.3 8.3 V Control Characteristics fMAX Maximum Output Frequency --- 150 --- kHz dMAX Buck Duty Cycle --- 100 --- % VCS Current Regulation Threshold 0.41 0.49 0.57 V VCS-HYS Current Regulation Hysteresis --- 100 --- mV RAMP Pin Charging Current --- 15 --- µA VRAMP+ RAMP Pin Shutdown Threshold --- 2.0 --- VRAMP- RAMP Pin Re-start Threshold --- 0.2 --- Dimming Duty Cycle 0 Dimming Characteristics IRAMP dPWM † 100 % VCC can be supplied from an alternative source for the IRS2980S to operate with bus voltages below this level. www.irf.com © 2011 International Rectifier 7 IRS2980S Electrical Characteristics VHV=100V, VCC= 14V, CVCC=0.1µF, CHVS=22nF and TA = 25°C unless otherwise specified. The output voltage and current (VO and IO) parameters are referenced to COM and are applicable to OUT. Symbol Definition Min Typ Max Units Test Conditions Gate Driver Output Characteristics (OUT) VOH High-Level Output Voltage --- VCC --- IO = 0A VOL Low-Level Output Voltage --- COM --- IO = 0A --- IO = 0A, VCC ≤ 8.0V VOL_UV --- UV-Mode Output Voltage COM tr Output Rise Time --- 120 220 tf Output Fall Time --- 50 80 IO+ Output source current --- 180 --- IO- Output sink current --- 260 --- www.irf.com ns mA © 2011 International Rectifier 8 IRS2980S I/O Pin Equivalent Circuit Diagrams www.irf.com © 2011 International Rectifier 9 IRS2980S Lead Definitions Pin # Symbol Description 1 HV High Voltage Bus 2 VS High Side Floating Supply Return 3 VCC VCC Supply 4 COM Ground / Common 5 ADIM Linear / Analog Dimming Input 6 RAMP Ramp Waveform for Analog Dimming 7 OUT 8 CS Gate Drive Output Load Current Sense Lead Assignments 1 VS 2 VCC 3 COM 4 IRS2980 HV www.irf.com 8 CS 7 OUT 6 RAMP 5 ADIM © 2011 International Rectifier 10 IRS2980S Application Information and Additional Details operating conditions imposed by the input and output voltages, output current and inductor value. The IRS2980S is primarily intended for use in Buck LED drivers operating with average current regulation using hysteretic control. The circuit topology uses a low side MOSFET referenced to the 0V bus driven by a low side gate driver circuit within the IRS2980S and an additional fast recovery freewheeling diode. In order to minimize switching losses the reverse recovery time of this diode should be no more than 35nS. The MOSFET should be selected for low capacitance to reduce switching losses and low gate charge (less than 25nC is recommended) to minimize gate drive current. The LED load is referenced to the DC bus and not 0V. The IRS2980S incorporates floating high side current sense inputs allowing the LED current to be sensed both when the MOSFET is switched on and off. This enables hysteretic operation, switching the MOSFET off when the current rises above an upper threshold and off when the current falls below a lower threshold. The current sense threshold Vcs is nominally 500mV with approximately 100mV of hysteresis making the upper limit Vcs+50mV and the lower limit Vcs-50mV. Some overshoot typically occurs due to propagation delays and a small undershoot is also possible. These vary depending on di/dt of the ripple current, which is a function of input and output voltage, inductor value and frequency as well as RC filter values (RF and CF). The average current is maintained at approximately the midpoint over a wide input and output voltage range due to the inherent accuracy of hysteretic control. The LED output current is set by selecting the value of the current sense resistor RCS. This is determined by the formula: The following diagram shows the rise and fall of the LED current as the MOSFET switches on and off: RCS = Figure 1: MOSFET gate drive and inductor/LED current. The following formulae model the operation of the IRS2980S based Buck LED driver: t on ≈ Q 0.2 ⋅ L ⋅ I LED + RF ⋅ C F + G + t dr VBUS _ DC − VLED 0.18 t off ≈ Q 0.2 ⋅ L ⋅ I LED + RF ⋅ C F + G + t df VLED 0.26 f SW = d= 1 (switching frequency) t on + t off t on (duty cycle) t on + t off Where, VCS I LED RF and CF are the current sense filter components, L is the inductor value, QG is the MOSFET gate charge, tdr and tdf are propagation delays (These values vary depending on circuit conditions, tdr decreases with input voltage. tdf is normally negligible. For a first order approximation these terms may be ignored.) Where ILED is the average LED output current. The peak to peak ripple ∆ILED will be 20% of the average LED current ILED due to the hysteretic operation plus some additional ripple due to circuit delays. These are caused mainly by the current sense filter and MOSFET gate drive. Since the IRS2980S uses hysteretic current control to switch the Buck MOSFET on and off, the LED current (which is equal to the inductor current) is maintained between upper and lower thresholds. Because of this the switching frequency and duty cycle vary to meet the www.irf.com © 2011 International Rectifier 11 IRS2980S pin of the IRS2980S is rated up to 450V, the actual maximum voltage that can be applied is limited by the by the power dissipation of the IC. The internal VCC regulator is recommended for use up to 200VDC or with a passive valley fill PFC circuit operating from up to 250VAC input. It can be operated at higher voltages only with sufficient heat sinking. Operating frequency and duty cycle will vary when there is ripple in the DC bus voltage. For example where a passive valley fill circuit is used for power factor correction (PFC) the LED current will be regulated dynamically by constantly changing frequency and duty cycle to maintain a constant average. Current Sense Filter Selection The recommended values for RF and CF are 100Ohms and 1nF. This is sufficient to prevent instability due to switching noise appearing at the current sense input. These values have negligible effect on the frequency and ripple. In a test application using a 3.3mH inductor to drive a 17.5V LED panel, the output current varied from 338mA to 347mA (2.7%) over a DC voltage input range of 40V to 200V. A resistor (RG) between the gate driver output and the gate of the power MOSFETs is also recommended to reduce switching transients by reducing dv/dt. A value of 10Ohms is recommended, however this can be increased to reduce noise if required. Filter values may be increased in order to lower the running frequency without increasing inductor size. This results in higher current ripple and higher current change over input voltage variations. This may be an acceptable compromise depending on the application specification. Figure 2: Passive valley fill PFC circuit Frequency Limiter The switching frequency of the IRS2980S is internally limited to approximately 150 kHz (fMAX). The IRS2980S is designed for use below this frequency in order to limit current consumption in the VCC and floating high side bias supplies. This is necessary because the IRS2980S uses internal regulators to supply these voltages, which can supply only a limited current. This restriction is acceptable in most LED driver applications. Where higher frequency operation is needed the IRS25401/11 is recommended. Figure 3: Passive valley fill PFC bus voltage (blue) and line input current (red) waveforms. The VCC current (ICC) drawn by the IRS2980S can be estimated from the following formula: I CC ≈ 1mA + QG ⋅ f SW High Voltage Regulator The IRS2980S includes a high voltage regulator to supply VCC from the DC input bus voltage. This eliminates the need for external VCC supply circuitry. A VCC capacitor of 1uF is recommended for reliable startup and smooth operation. The IRS2980S may shut down if CVCC is not present or too small. If necessary the internal regulator may also be bypassed by supplying an external DC supply from 14V to 15V to the VCC pin. Although the HV Therefore power dissipation due to the high voltage regulator can be calculated as: PREG = VBUS _ DC _ AV ⋅ I CC Floating Differential Current Sense The floating high side current sense incorporated in the IRS2980S is able to operate up to 450V and withstand voltage surges up to 600V. An internal bias supply is derived between the HV and VS www.irf.com © 2011 International Rectifier 12 IRS2980S pins by a 1mA current source pulling down on VS so that a supply voltage is produced across the external capacitor CHVS to supply the high side circuitry. A value of 22nF is recommended for CHVS. The internal bias supply also dissipates some power, which can be calculated from the formula: PBIAS = (VBUS _ DC _ AV − 10) ⋅1mA In order for the high side current sense circuitry to function, a minimum bus voltage of 30V is required to provide adequate bias supply current and standoff voltage. Figure 4: Thermal relief example In addition if the IRS2980S is used in an application where the circuit is encapsulated in thermally conductive filler the die temperature rise is also greatly reduced. Figure 4 shows an example of thermal relief placed around the IRS2980S in a high voltage application. The top side copper layer is shown as red and the bottom side is blue. With thermal relief ∆T becomes: Thermal Considerations Since the IRS2980S dissipates some power during normal operation, temperature rise of the IC die must be considered as part of the design process. The SO8 IC package has a maximum power rating (PD) of 625mW, therefore the sum of PREG and PBIAS should not exceed this value. The junction temperature should remain below 125°C to ensure operation within specifications. The junction temperature is normally 10°C above the case temperature for an SO8 package therefore the case temperature should not exceed 115°C at maximum ambient. The junction to ambient thermal resistance of the package (RθJA) is 128°C/W. This would give an 80°C temperature rise without any thermal relief at the maximum PD value of 625mW. ⎡ RθJA ⋅ RθHS ⎤ ΔT = PD ⋅ ⎢ ⎣ RθJA + RθHS ⎥⎦ Where RθHS is the thermal resistance of the thermal relief area or heat sink, which will normally be lower than RθJA. Dimming The IRS2980S includes a PWM dimming oscillator that generates a linear ramp waveform at the RAMP pin with the frequency determined by an external capacitor to COM (CRAMP). A DC voltage is applied to the ADIM pin which is compared to this ramp to produce a gating signal that enables and disables the high frequency switching of the MOSFET gate drive. By varying the ADIM voltage the duty cycle is adjusted allowing brightness to be adjusted from zero to 100%. This is accomplished by operating the LED driver in burst mode and varying the duty cycle of the bursts. The LED current during dimming is shown in figure 5: ΔT = PD ⋅ RθJA In order to reduce the junction temperature rise thermal relief should be added around the IRS2980S on the PCB. With adequate thermal relief the die temperature rise can be greatly reduced. The recommended method is to place an area of copper on the opposite side of the PCB to the IC in the same position with several vias added underneath the IC to conduct heat through to the other side. www.irf.com © 2011 International Rectifier 13 IRS2980S being used in dim mode place a capacitor CDIM from the ADIM pin to COM and keep the capacitor as close to the IC as possible with the shortest possible traces. 4) If the IRS2980S is being used in non-dimming mode the RAMP pin can be connected to COM. If it is being used in dimming mode CRAMP should be located close to the IC with the shortest possible traces to the RAMP pin and COM. 5) Connect IC COM to power GND at one connection only. Do NOT route power GND through the programming components or IC COM. Figure 5: LED current during dimming. The dimming level can also be controlled from a digital input by replacing CRAMP with a 68k resistor. This sets a DC threshold at the RAMP pin to approximately 1V so that a logic level PWM dimming control signal can be applied to the ADIM pin to directly switch the output on and off. PCB Layout Guidelines Proper care should be taken when laying out a PCB board ensure correct functionality of the IRS2980S. Transients caused by high dV/dt during switching could potentially cause some false triggering of the hysteretic circuit therefore a small filter comprising RF and CF is recommended. CF should be located close to the IC pins with the trace from HV to RCS and the traces from RCS to CS through RF kept as short as possible. The 0V load return power ground should be connected to the IC COM pin and at a single point to avoid ground loops. The values of RF and CF are normally chosen to provide noise filtering without adding excessive delay to the circuit, however in some case these are deliberately made larger to lower the running frequency as this reduces switching losses and ICC current. The following guidelines should be followed during PCB board layout: 1) Place VCC supply decoupling capacitor (CVCC) as close as possible to the VCC and COM pins. 2) Place high side decoupling capacitor (CVF) as close as possible to the HV and VS pins. 3) If the IRS2980S is being used in non-dimming mode connect the ADIM pin to VCC. If it is www.irf.com © 2011 International Rectifier 14 IRS2980S Package Details www.irf.com © 2011 International Rectifier 15 IRS2980S Tape and Reel Details LOADED TAPE FEED DIRECTION A B H D F C NOTE : CONTROLLING DIM ENSION IN M M E G CARRIER TAPE DIMENSION FOR Metric Code Min Max A 7.90 8.10 B 3.90 4.10 C 11.70 12.30 D 5.45 5.55 E 6.30 6.50 F 5.10 5.30 G 1.50 n/a H 1.50 1.60 8SOICN Imperial Min Max 0.311 0.318 0.153 0.161 0.46 0.484 0.214 0.218 0.248 0.255 0.200 0.208 0.059 n/a 0.059 0.062 F D C B A E G H REEL DIMENSIONS FOR 8SOICN Metric Code Min Max A 329.60 330.25 B 20.95 21.45 C 12.80 13.20 D 1.95 2.45 E 98.00 102.00 F n/a 18.40 G 14.50 17.10 H 12.40 14.40 www.irf.com Imperial Min Max 12.976 13.001 0.824 0.844 0.503 0.519 0.767 0.096 3.858 4.015 n/a 0.724 0.570 0.673 0.488 0.566 © 2011 International Rectifier 16 IRS2980S Part Marking Information Part number IRSxxxxx Date code YWW ? Pin 1 Identifier ? MARKING CODE P Lead Free Released IR logo ? XXXX Lot Code (Prod mode – 4 digit SPN code) Assembly site code Per SCOP 200-002 Non-Lead Free Released www.irf.com © 2011 International Rectifier 17 IRS2980S Ordering Information Standard Pack Base Part Number IRS2980S Package Type SOIC8N Complete Part Number Form Quantity Tube/Bulk 95 IRS2980SPBF Tape and Reel 2500 IRS2980STRPBF The information provided in this document is believed to be accurate and reliable. However, International Rectifier assumes no responsibility for the consequences of the use of this information. International Rectifier assumes no responsibility for any infringement of patents or of other rights of third parties which may result from the use of this information. No license is granted by implication or otherwise under any patent or patent rights of International Rectifier. The specifications mentioned in this document are subject to change without notice. This document supersedes and replaces all information previously supplied. For technical support, please contact IR’s Technical Assistance Center http://www.irf.com/technical-info/ WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105 www.irf.com © 2011 International Rectifier 18