TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode SOT-89 Pin Definition: 1. Drain 2. GND 3. VDD General Description The TS19451 is a PWM high efficiency LED driver control IC. It allows efficient operation of LED strings from voltage source ranging up to 400VDC. It includes an internal high voltage switching MOSFET controlled with fixed off-time of approximately 10.5µS. The LED string is driven at constant current, thus providing constant light output and enhanced reliability. The output current is internally fixed at 50mA. The peak current control scheme provides good regulation of the output current throughout the universal AC line voltage range of 85~264VAC or DC input voltage of 20~400V Features Typical Application Circuit ● Constant output current at 50mA ● Universal 85~264VAC operation ● Fixed off-time buck converter ● Internal 475V power MOSFET Application ● Decorating LED lighting ● Lower power lighting fixtures ● Back light of flat panel displays Ordering Information Part No. Package Packing TS19451CY RMG SOT-89 1Kpcs / 7” Reel Note: “G” denotes for Halogen Free Absolute Maximum Rating Parameter Symbol Limit Unit VIN to GND ~ +475 V Supply Current IDD 5 mA Power Dissipation @ TA=25ºC PD 1300 mW Operating Ambient Temperature TOPR -40 to +85 ºC Storage Temperature Range TSTG -65 to +150 o -40 to +150 o Input Voltage Range Junction Temperature Range TJ Thermal Resistance – Junction to Ambient RθJA 128 C C o C/W Note: Stresses beyond those listed under ”Absolute Maximum Ratings” may cause permanent damage to the device. These are stress rating only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 1/7 Version: B11 TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode Electrical Specifications (Ta = 25oC, VDRAIN= 50V, unless otherwise noted) Function Parameter Symbol Test Conditions Min Typ Max Units VDD -- 7.5 -- V Drain Supply Voltage VDRAIN -- 20 -- V Undervoltage Lockout Threshold UVLO 4.0 -- -- V Undervoltage Lockout Hysteresis ∆UVLO -- 200 -- mV -- 200 350 µA 475 -- -- V Internal Regulator Internally Regulated Voltage Supply Current IDD VDD(EXT)=8.5V, VDRAIN=40V Output (Drain) Breakdown Voltage VBR On Resistance RDSON IDRAIN=50mA -- -- 210 Ω Output Capacitance CDRAIN VDRAIN=400V -- 1.0 5.0 pF ISAT 100 150 -- mA ITH 49 -- 63 mA Leading edge Blanking delay TBLANK 200 300 400 nS Minimum Turn On-Time TON(MIN) -- -- 650 nS TOFF 8 10.5 13 µS MOSFET Saturation current Current Sense Comparator Threshold Current Off-Time Generator Turn On-Time Note 1: The specification which apply over the full operating ambient temperature range of -40ºC<TA<+85ºC 2: Guaranteed by design Block Diagram 2/7 Version: B11 TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode Function Description The TS19451 is a PWM peak current controller for controlling a buck converter topology in continuous conduction mode (CCM). The output current is internally preset at 50mA When the input voltage of 20~400V appears at the Drain pin, the internal high-voltage linear regulator seeks to maintain a voltage of 7.5VDC at the VDD pin. Until this voltage exceeds the internally programmed under-voltage threshold, the output switching MOSFET is non-conductive. When the threshold is exceeded, the MOSFET turns on. The input current begins to flow into the Drain pin. Hysteresis in provided in the under-voltage comparator to prevent oscillation. When the input current exceeds the internal preset level, a current sense comparator resets an RS flip-flop, and the MOSFE turns off, At the same time, a one-shot circuit is activated that determines the duration of the off-state (10.5µS typ.) As soon as this time is over, the flip-flop sets again. The new switching cycle begins. A “blanking” delay of 300nS is provided that presents false triggering of the current sense comparator due to the leading edge spike caused by circuit parasitic. Application Information The TS19451 is specifically designed for driving multi LED strings. It can be operated from either universal AC line range of 85~264VAC or 20~400VDC, and drives up to tens of high brightness LEDs. All LEDs can be run in series and this device regulates at constant current, yielding uniform illumination. It’s also compatible with triac dimmers. Selecting L1 and D1 There is a certain trade-off to be considered between optimal sizing of the output inductor L1 and the tolerated output current ripple. The required value of L1 is inversely proportional to the ripple current ∆IO in it. L1 = (VO x TOFF) / ∆IO VO is the forward voltage of the LED string. TOFF is the off-time of the TS19451. The output current in the LED string (IO) is calculated as: IO = IH – (∆IO / 2) Where ITH is the current sense comparator threshold. The ripple current introduces a peak-to-average error in the output current setting that needs to be accounted for. Due to constant off-time control technique used in the TS19451, the ripple current is independent of the input AC or DC line voltage variation. Therefore, the output current will remain unaffected by the varying input voltage. According a filter capacitor across the LED string can reduce the output current ripple even further, thus permitting a reduced value of L1. However, one must keep in mind that the peak-to-average current error is affected by the variation of TOFF. Therefore, the initial output current accuracy might be sacrificed at large ripple current in L1. Another important aspect of designing an LED driver with TS19451 is related to certain parasitic elements of the circuit, including distributed coil capacitance of L1, junction capacitance and reverse recover of the rectifier diode D1, capacitance of the PCB traces CPCB and output capacitance CDRAIN of the controller itself. These parasitic elements affect the efficiency of the switching converter and could potentially cause false triggering of the current sense comparator if not properly managed. Minimizing these parasitic is essential for efficient and reliable operation of the TS19451. Coil capacitance of inductors is typically provided in the manufacturer’s data books either directly or in terms of the self-resonant frequency (SRF). 3/7 Version: B11 TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode Application Information (Continue) L is the inductance value, and CL is the coil capacitance. Charging and discharging this capacitance every switching cycle causes high-current spikes in the LED string. Therefore, connecting a small capacitor CO(~10nF) is recommended to bypass these spikes. Using an ultra-fast rectifier diode for D1 is recommended to achieve high efficiency and reduce the risk of false triggering of the current sense comparator. Using diodes with shorter reverse recovery time trr and lower junction capacitance CJ achieves better performance. The reverse voltage rating VR of the diode must be greater than the maximum input voltage of LED lamps. The total parasitic capacitance present at the Drain pin of the TS19451 can be calculated as: CP = CDRAIN + CPCB + CL + CJ When the switching MOSFET turns on, the capacitance CP is discharged into the Drain pin of the IC. The discharge current is limited to about 150mA typically. However, it may become lower at increased junction temperature. The duration of the leading edge current spike can be estimated as: TPSIKE = ((VIN x CP) / (ISAT)) + tr In order to avoid false triggering of the current sense comparator, CP must be minimized in accordance with the following expression: Where TBLANK(MIN) is the minimum blanking time of 200ns, and VIN(MAX) is the maximum instantaneous input voltage. EMI Filter As with all off-line converters, selecting an input filter is critical to obtaining good EMI. A switching side capacitor, albeit of small value, is necessary in order to ensure low impedance to the high frequency switching currents of the converter. As a rule of thumb, this capacitor should be approximately 0.1~0.2µF/W of LED output power. Typical Application Circuit for Universal 85~264VAC LED Lamps Driver 4/7 Version: B11 TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode Electrical Characteristics Curve Figure 1. Threshold Current vs. Junction Temperature Figure 2. Drain Breakdown Voltage vs. Output Current Figure 3. OFF-Time vs. Junction Temperature Figure 4. Drain Capacitance vs. Drain Voltage Figure 5. On-Resistance vs. Junction Temperature Figure 6. Drain Current vs. Drain Voltage 5/7 Version: B11 TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode SOT-89 Mechanical Drawing DIM A B C D E F G H I J SOT-89 DIMENSION MILLIMETERS INCHES MIN MAX MIN MAX 4.40 4.60 0.173 0.181 1.50 1.7 0.059 0.070 2.30 2.60 0.090 0.102 0.40 0.52 0.016 0.020 1.50 1.50 0.059 0.059 3.00 3.00 0.118 0.118 0.89 1.20 0.035 0.047 4.05 4.25 0.159 0.167 1.4 1.6 0.055 0.068 0.35 0.44 0.014 0.017 Marking Diagram Y M L = Year Code = Month Code for Halogen Free Product (O=Jan, P=Feb, Q=Mar, R=Apl, S=May, T=Jun, U=Jul, V=Aug, W=Sep, X=Oct, Y=Nov, Z=Dec) = Lot Code 6/7 Version: B11 TS19451 AC/DC WLED Driver with Internal MOSFET Universal Switch Mode Notice Specifications of the products displayed herein are subject to change without notice. TSC or anyone on its behalf, assumes no responsibility or liability for any errors or inaccuracies. Information contained herein is intended to provide a product description only. No license, express or implied, to any intellectual property rights is granted by this document. Except as provided in TSC’s terms and conditions of sale for such products, TSC assumes no liability whatsoever, and disclaims any express or implied warranty, relating to sale and/or use of TSC products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual property right. The products shown herein are not designed for use in medical, life-saving, or life-sustaining applications. Customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify TSC for any damages resulting from such improper use or sale. 7/7 Version: B11