Technology. SCT2004 V02_01; May/09. 4-Channel. Constant Current Driver. Product Description. Features

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1 StarChips Technology 4-Channel Constant Current Driver Product Description V02_01; May/09 The is a four channels constant current driver best for LED lighting. It provides the PWM control effect by sinking constant current from LED clusters with minimum pulse width 80ns. The PWM control is performed by connecting the PWM signal from system control unit to pin of the. The full scale current value of each output is set by an external resistor connected to REXT pin. The guarantees to endure maximum DC 24V at each output port. Each output of can sink a constant current up to 320mA. Users can simply shunt the outputs to get higher current driver-ability, especially in the case of high power LED lighting. The excellent current regulation capability allows easily drive each output current to a constant stable output nearly without affected by power supply of LED, loading due to variant V F of LEDs and operating temperature. The is equipped with over temperature protection. The four channels IC stops driving the output while junction temperature exceeds 180 C the highest limit and the output will be reactivated while the junction temperature is below the 130 C the low limit of reactivation. Furthermore, with negative temperature coefficient characteristics the driver system and LEDs are protected from damage of thermal runaway or overheated. Features Four constant-current outputs rate at 24V Constant current range: mA Excellent regulation to load, supply voltage and temperature Minimum PWM pulse width 80ns ±2%(typ) current matching between outputs ±4%(typ) current matching between ICs Low dropout output 0.4V@80mA All output current are adjusted through one external resistor Built-in power on reset and thermal protection Supply voltage range V Dimming control with Schmitt triggered input Package: SOP8 with heat sink pad Application: LED lighting, LED backlight, LED lamp Page 1 of 11

2 Block Diagram OUT1 OUT2 OUT3 OUT4 R EXT Current Regulator Output Driver Pin Configuration 1 2 OUT1 3 OUT2 4 CSOG (TP) 8 VDD 7 REXT 6 OUT4 5 OUT3 Terminal Description Pin No. Pin Name Function 1 Ground terminal 2 Input terminal of output enable signal. Output is enabled when is high. 3~6 OUT1~4 Output terminals with constant current 7 REXT Input terminal connected to an external resistor for setting up all output current 8 VDD Supply voltage terminal Equivalent Circuits of Inputs Page 2 of 11

3 Ordering information Part Package Unit per reel(pcs) Marking CSOG Green SOP8(150mil) with thermal pad CSOG Maximum Ratings (T A = 25 C) Characteristic Symbol Rating Unit Supply voltage 7 V Input voltage V IN -0.2 ~ +0.2 V Output current I OUT 360 ma/channel Output voltage V OUT 24 V Total terminals current I 1500 ma Power dissipation(free Air) SOP8 P D 2.08 W Thermal resistance(free Air) SOP8 R TH(j-a) 60 C /W Operating temperature T OPR -40~+85 C Storage temperature T STG -55~+150 C Recommended Operating Conditions (T A =-40 to 85 C unless otherwise noted) Characteristic Symbol Conditions Min. Typ. Max. Unit Supply voltage V Output voltage V OUT Output OFF V Output ON V Output current I OUT DC test condition ma V IH V Input voltage V IL V pulse width t w = V ns Page 3 of 11

4 Electrical Characteristics ( =5V, T A =25 C unless otherwise noted) Characteristic Symbol Conditions Min. Typ. Max. Unit Input voltage Output leakage current V IH V V IL V I OL V OUT = 24V ua Output current I OUT V OUT =1V R EXT =900Ω ma Current channel skew * di OUT1 V OUT =1V R EXT =900Ω - ±2 ±3 % Current chip skew Line regulation I OUT vs. Load regulation I OUT vs. V OUT Pull-down resistor Thermal shutdown Supply current OFF ON di OUT2 V OUT =1V R EXT =900Ω - ±4 ±6 % %/d 4.5V < < 5.5V R EXT =900Ω, V OUT > 1V %/dv OUT 1V < V OUT < 4V, R EXT =900Ω, =5V - - ±1 %/V - - ±1 %/V R DOWN KΩ T H C Junction Temperature C T L I DD(OFF)1 I DD(OFF)2 I DD(ON) * Skew=(I OUT -I AVG )/I AVG, where I AVG =(I max + I min )/2 R EXT = Open, OUT 1 ~OUT 4 =OFF R EXT = 900Ω, OUT 1 ~OUT 4 =OFF R EXT = 900Ω, OUT 1 ~OUT 4 =ON ma Page 4 of 11

5 Switching Characteristics ( =5V, T A =25 C unless otherwise noted) Characteristic Symbol Condition Min. Typ. Max. Unit Propagation delay time - OUTn t PLH ns ( L to H ) = 5V Propagation V LED = 5V delay time - OUTn t V IH = PHL ns ( H to L ) V IL = R EXT = 900Ω Pulse width t w R ns L = 47Ω Output rise time of I OUT t OR C L = 10pF ns Output fall time of I OUT t OF ns Test Circuit for Switching Characteristics I DD V LED V IL V IH VDD OUT1 I OUT t R = t F = 10 ns OUT2 C L R EXT OUT4 REXT R L V OUT Timing Waveform 50% t PHL t W 50% t PLH OUTn 90% 50% 10% 50% 10% 90% t OF t OR Page 5 of 11

6 Adjusting Output Current All s output current (I OUT ) are set by one external resistor at pin REXT. The output current I OUT versus resistance of R EXT is shown as the following figure I O UT vs. R EXT IOUT(mA) V<V OUT <4V R EXT (KΩ) Furthermore, when the s output voltage is set between 1 Volt and 4 Volt, the output current can be estimated approximately by: I OUT = 120(630 / R EXT ) (ma) (chip skew < ±6%). Thus the output current are set about 84mA at R EXT = 900Ω. Output Characteristics The current characteristic of output curve is flat. The output current can be kept constantly regardless of the variations of LED forward voltage when V OUT > 1V. The relationship between I OUT and V OUT is shown below: 400 I OUT vs. V O UT IOUT(mA) V O UT (V) Page 6 of 11

7 Maximum Power Dissipation The maximum power dissipation (P D(max) ) of a semiconductor chip varied to different package and ambient temperature. It s determined as P D(max) =(T J(max) T A )/R TH(j-a) where T J(max) : maximum chip junction temperature usually considered as 150 C, T A : ambient temperature, R TH(j-a) : thermal resistance. Since P=IV, for sink larger I OUT, users are encouraged to add proper voltage reducers on output to reduce the heat generated from the. 2.5 P D(max) vs. T A 2 PD(max)(W) SOP8:R TH(j-a) = 60 C/W T A ( C) Limitation on Maximum Output Current The maximum output current vs. duty cycle is estimated by: I OUT(max) =(((T J(max) -T A )/R TH(j-a) )-( *I DD ))/V OUT /Duty/N, where T J(max) =150 C, N=4(all ON) I OUT(max) vs. Duty SOP8 IOUT(max)(mA) VDD=5V, V O UT =1.5V, TA=85 C Duty(%) Page 7 of 11

8 Load Supply Voltage (VLED) The can be operated very well when V OUT ranging from 1V to 4V. It is recommended to use the lowest possible supply voltage or set a voltage reducer to reduce the V OUT voltage, at the same time reduce the power dissipation of the. Follow the diagram instructions shown below to lower down the output voltage. This can be done by adding additional resistor or zener diode, thus V OUT =V LED -V DROP -V F. V LED V LED V DROP V DROP I OUT V F I OUT V F V OUT V OUT Over Temperature Shutdown The contains thermal shutdown scheme to prevent damage from over heated. The internal thermal sensor turns off all outputs when the die temperature exceeds ~ +180 C. The outputs are enabled again when the die temperature drops below ~ +130 C. Page 8 of 11

9 Typical Application Circuits (1) Lighting with recommended =5V OUT1, ,4 SOP ,6 VDD REXT OUT3,4 R EXT (2) Lighting with > 5V, e.g. =12V/24V R1 ~5V OUT1, ,4 SOP ,6 VDD REXT OUT3,4 ZD1 R EXT C1 (3) Lighting with dimming control V LED PWM Pulse OUT1, ,4 SOP ,6 VDD REXT OUT3,4 R EXT Page 9 of 11

10 PCB Design Considerations Use the following general guide-line when designing printed circuit boards (PCB) : Decoupling Capacitor Place a decoupling capacitor e.g. 4.7uF between VDD and pins of the. Locate the capacitor as close to the as possible. The necessary capacitance depends on the LED load current and dimming frequency. V LED 10Ω 4.7uF VDD REXT External Resistor (R EXT ) Locate the external resistor as close to the REXT pin in as possible to avoid noise. Power and Ground Maximizing the width and minimizing the length of and trace improve efficiency and ground bouncing by effect of reducing both power and ground parasitic resistance and inductance. A small value of resistor e.g. 10Ω series in power input of the in conjunction with decoupling capacitor shunting the ICs is recommended. Separating and feeding the LED power from another stable supply terminal VLED is strongly recommended. Page 10 of 11

11 Package Dimension SOP8TP(check up-to-date version) D θ L L1 E1 E y B e A1 A2 A 0.20 mm GAUGE PLANE Symbol Dimension (mm) Dimension (mil) Min. Nom. Max. Min. Nom. Max. A A A B c D E E e L L y θ Revision History (check up-to-date version) c Data Sheet Version V02_01 Remark Descriptions added Information provided by StarChips Technology is believed to be accurate and reliable. Application circuits shown, if any, are typical examples illustrating the operation of the devices. Starchips can not assume responsibility and any problem raising out of the use of the circuits. Starchips reserves the right to change product specification without prior notice.