WS3442A Constant Current Controller for Non-isolated Buck LED Driver Features General Description � Inductor Current Critical Mode, No Need to The WS3442A is a high precision constant current Compensate the Inductance Variation controller，designed for non-isolated buck LED driver. It � 550V MOSFET integrated can operate under universal AC input or 12V~550V DC � Source Driver Structure, Not Need the Auxiliary input. Winding for VCC The WS3442A integrates 550V power MOSFET, so it can � ±3% LED Current Accuracy achieve excellent constant current performance with very � Up to 93% System Efficiency few external components. � LED Open/Short Circuit Protection The WS3442A uses high precision current sense circuit � Current Sense Resistor Short Circuit Protection and patent method for constant current control, to achieve � Over Temperature Protection high precision output current and excellent line regulation. � Programmable LED open protection The WS3442A operates in inductor current critical mode. � Frequency shuffling The LED current is constant over wide range of inductance variation and the LED output voltage, so the Applications load regulation is excellent. � LED Bulb The WS3442A uses patent source driver architecture. The � LED Candle light operation current is 200uA only, so the auxiliary winding is � LED Spot light not needed. It can simplify the system design and reduce � Decorative LED lighting the system cost. � T5/T8 Lamp The WS3442A offers rich protection functions, including � Ceiling Lamp LED open/short circuit protection, current sense resistor � Flat Lamp short circuit protection and over temperature protection. Typical Application Circuit AC 1 G ND CS 8 2 ROV P CS 7 3 VCC D R A IN 6 4 S O URCE D R A IN 5 W/T-DS028-Rev.A/ 0 Nov.2013 Copyright@Winsemi Microelectronics Co., Ltd., All right r eserved. 1113 WS3442A Pin Definition and Device Marking WS3442A is available in DIP-8 package. 1 RO VP 2 VCC 3 So u rc e 4 WS3442AD8P AXB YM GND 8 CS 7 CS WS3442AD8P: Product code A: Product Code X：Internal Code 6 D R A IN B：Area Code 5 D R A IN YM：Year, Month Pin Function Description Pin Name Pin NO. Description GND 1 Ground ROVP 2 Programmable LED open protection pin，connect a resistor to GND VCC 3 Power supply Source 4 Source driver output, connect to the source of power-mos DRAIN 5,6 Internal HV power MOSFET drain CS 7,8 Current sense input, the sense resistor is connected from CS to ground Block Diagram VCC 3 D r a in 5 ,6 Soft-Driver GND 1 UVLO Inter s upply Zero-Current Detec t 400mV L in e c ompens ation OCP 4 So u r c e L o g ic & dr iv er CS Shor t RO VP 2 L ED OPEN PR O TEC TIO N LED Shor t O TP CS 7 ,8 2/7 Steady, keep you advance WS3442A Ordering Information Package Part Number Marking 8-Pin DIP-8, Pb-free WS3442AD8P WS3442AD8P Recommended Operating Condition symbol symbol parameter value units WS3442A P output power < 28 W Absolute Maximum Ratings symbol parameter Range Units VDS I CC_MAX Internal HV MOSFET drain voltage -0.3~550 V VCC pin maximum sink current 2.5 mA VROVP VCS ROVP input voltage -0.3~7 V Current sense pin input voltage -0.3~7 V PDMAX TJ Power dissipation 0.9 W Operating junction temperature 150 ℃ TSTG Storage temperature range -55~150 ℃ Note: Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Under “recommended operating conditions” the device operation is assured, but some particular parameter may not be achieved. 3/7 Steady, keep you advance WS3442A Electrical Characteristics (Unless otherwise specified，TA=25℃，VCC=16V) Symbol Parameter Conditions Min Typ Max Units Supply Voltage Section Vcc_clamp VCC Clamping Voltage - 18 - V Icc_clamp VCC Clamping Current - - 2.5 mA VCC_ST VCC Start Up Voltage 12 13.1 14.5 V VCC Falling - 4.3 - V VCC<VCC_ST-0.5V - - 50 uA - 200 - uA 390 400 410 mV Vuvlo_HYS VCC Rise VCC Under Voltage Latch Out Hysteresis Ist Start Up Current Iop Operation Current Current Sensor Section Vcs_th Current Sensor Voltage Threshold TLEB Leading Edge Blanking - 350 - ns TDELAY Turn Off Delay Time - 300 - ns Internal Driver Section TOFF_MIN Minimum Demagnetization Time - 4 - us TOFF_MIN Maximum Demagnetization Time - 130 - us TON_MAX Maximum Turn On Time - 40 - us - - 6.5 ohm 550 - - V Internal HV MOSFET RDSON Switch ON Resistance VGS =10V,I D=1.0A VDS_BD Drain to Source voltage I D=250μA Over Temperature Section TSD Thermal Shut Down Temperature - 150 - ℃ TSD_HYS Thermal Shut Down Hysteresis - 30 - ℃ 4/7 Steady, keep you advance WS3442A The IPK is the peak current in inductor. Function Description WS3442A is a constant current controller, designed for driving non-isolated buck LED power supply. WS3442A Line Compensation integrates 550V power MOSFET, and it uses patent constant current control method and source driver The WS3442A integrates line compensation function. structure, excellent constant current characteristic is Excellent line regulation is achieved. achieved with low counts components. Low cost and high efficiency of system is realized. Source Driver Structure Start up The WS3442A uses the patent source driver structure. The typical operation current is as low as 200uA, the The Vcc will be charged through the startup resistor auxiliary winding is not need. So the system design is when the system is powered on. When the voltage on simple and the cost is low. Vcc reaches the startup voltage threshold, the controller starts to switching. The Vcc voltage of WS3442A is clamped to 1 8V by internal Zener diode. Inductance Calculation Constant The WS3442A is designed to work in inductor current Current Control and Output Current critical mode, the energy will be stored in the inductor Setting when the MOSFET is turned on. The turn on time is The WS3442A uses patent constant current control method, excellent constant current is achieved with low counts components. The WS3442A senses the peak current in inductor cycle by cycle. The CS Pin is connected to the input of internal current comparator, and compared with the internal 400mV reference voltage. The external power MOSFET will be turned off when the CS pin voltage reaches the voltage threshold. The comparator has a 350ns LEB timer to avoid mis-trigger. given by: t on = L × I PK VIN − VLED The L is the inductance. The Ipk is the peak current in inductor. The VIN is the input rectified voltage. The VLED is the voltage on LED. When the power MOSFET is turned off, the inductor current will decrease from the peak current to zero. The turn off time is given b y: The peak current in the inductor is given by: I PK t off = 400 = ( mA) RCS The Rcs is the resistance of current sense resistor The current in LED can be calculated by the following The MOSFET will be turned on again when it detects the inductor current goes to zero. The inductance can be calculated by the following equation: equation: I LED = L × I PK VLED I PK 2 5/7 Steady, keep you advance WS3442A L= VLED × (VIN − VLED ) f × I PK × VIN In which the Vcs is the OCP threshold (0.4V) ,the Vovp is The f is the system switching frequency, which is the new target output protection voltage. And the value of the resistor Rovp is as below: proportional to the input voltage. So the minimum switching frequency is set at lowest input voltage, and maximum switching frequency is set at highest input Rovp = 15 * Tovp * 10 6 （KΩ） Protection Functions voltage. The WS3442A internally set the minimum off time to 4us and maximum off time to 130us. When the inductance is very small, the toff may goes below the minimum off time and the inductor current becomes discontinuous. So the output LED current will be smaller than the setting value. If the inductance is too large, the toff may goes beyond the maximum off time and the inductor current becomes continuous. And the output LED current will be larger than the setting value. So it’s very important to select a The WS3442A has many protection functions, including LED open/short circuit protection, current sense resistor short circuit protection and over temperature protection. All of the protection functions are designed to auto-recover. The over temperature protection circuitry in the WS3442A monitors the die junction temperature after start up. When the temperature rises to 150℃, the power MOSFET will be shut down immediately and maintains at switch off condition until the temperature on die falls right inductance. The WS3442A also internally set the maximum on time 30℃ below the thermal protection trigger point. to 40us. When the input voltage is very low or LED output voltage is very high, the ton may goes beyond the PCB Layout maximum on time. The power MOSFET will be turned off even the inductor current still below the setting value. So the output LED current will be smaller than the setting The following guidelines should be followed in WS3442A PCB layout: Bypass Capacitor value. The bypass capacitor on VCC pin should be as close as possible to the VCC and GND pins. Set open protection Ground Path The LED open protection voltage can be set by adjusting the value of the resistor connecting from ROVP to GND. The power ground path for current sense should be short, and the power ground path should be separated from small signal ground path before the negative node of the Rovp voltage is 0.5V. In the LED open condition, the output voltage will raise graduate, and the demagnetize time will shorten as well, the demagnetize time Tovp can be calculator as below: bus capacitor. The Area of Power Loop The area of main current loop should be as small as possible to reduce EMI radiation. And the controller L × V CS Tovp = R CS × V OVP （KΩ） should be placed away. from the heat generator, such as the power diode. 6/7 Steady, keep you advance WS3442A Package Information DIP-8 Package Outline Dimensions D2 θ1 C1 C C4 θ2 C2 C3 θ3 A2 A5 A1 D1 A3 D A4 B A Winsemi Symbol Dimensions in Millimeters Dimensions in Inches Min Max Min Max A 9.00 9.50 0.354 0.374 B 6.10 6.60 0.240 0.260 C 3.0 3.4 0.118 0.134 A1 1.474 1.574 0.058 0.062 A2 0.41 0.53 0.016 0.021 A3 2.44 2.64 0.096 0.104 A4 0.51TYP 0.02TYP A5 0.99TYP 0.04TYP C1 6.6 C2 7.30 0.260 0.50TYP 0.287 0.02TYP C3 3.00 3.40 0.118 0.134 C4 1.47 1.65 0.058 0.065 D 7.62 9.3 0.300 0.366 D1 0.24 0.32 0.009 0.013 D2 7.62TYP 0.3TYP W/T-DS028-Rev.A/ 0 Nov.2013 Copyright@Winsemi Microelectronics Co., Ltd., All right r eserved. 1113