Constant Current Driver Product Description

Transcription

1 StarChips Technology 8-Channel Constant Current Driver Product Description V02_02; Nov/12 The is an eight 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 160mA. Users can simply shunt the outputs to get higher current driver0ability, 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 negative temperature coefficient characteristics, thus the driver system and LEDs are protected from damage of thermal runaway or overheated. Features Eight constant0current 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@40mA All output current are adjusted through one external resistor Built0in power on reset and thermal protection Supply input voltage: 5V Dimming control with Schmitt triggered input Package: SSOP16 with heat sink pad Application: LED lighting, LED backlight, LED lamp Page 1 of 12

2 Pin Configuration 1 NC 2 NC 3 4 OUT1 5 OUT2 6 OUT3 7 OUT4 8 CSSG (TP) 16 VDD 15 REXT 14 NC 13 NC 12 OUT8 11 OUT7 10 OUT6 9 OUT5 Terminal Description Pin Name Pin No. I/O 1 0 Ground terminal NC 2,3,13,14 0 No connection 4 I Function Input terminal of output enable signal. Output is enabled when is high. OUT1~8 5~12 O Output terminals with constant current REXT 15 I/O VDD 16 0 Supply voltage terminal Input terminal connected to an external resistor for setting up all output current TP 0 0 Thermal pad, please connect TP to ground. Block Diagram OUT1 OUT2 OUT8 POR Current Regulator with Thermal Protection Output Driver Equivalent Circuits of Inputs V DD V DD Page 2 of 12

3 Ordering information Part Marking Package Unit per reel(pcs) CSSG 2008CSSG Green SSOP16(150mil) with thermal pad 2500 StarChips Technology, Inc. 4F, No.5, Technology Rd., ScienceBased Industrial Park, HsinChu, Taiwan, R.O.C. Tel : Ext.555 Fax: service@starchips.com.tw Maximum Ratings (T A = 25 C) Characteristic Symbol Rating Unit Supply voltage V DD 7 V Input voltage V IN 00.2 ~ V DD +0.2 V Output current I OUT 180 ma/channel Output voltage V OUT 24 V Total terminals current I 1200 ma Power dissipation SSOP16TP P D 2.08 W Thermal resistance SSOP16TP R TH(j0a) 60 C /W Operating temperature T OPR 040~+85 C Storage temperature T STG 055~+150 C The absolute maximum ratings are a set of ratings not to be exceeded. Stresses beyond those listed under Maximum Ratings may cause the device breakdown, deterioration even permanent damage. Exposure to the maximum rating conditions for extended periods may affect device reliability. Recommended Operating Conditions (T A =040 to 85 C unless otherwise noted) Characteristic Symbol Conditions Min. Typ. Max. Unit Supply voltage V DD V Output voltage V OUT Output OFF V Output ON V Output current I OUT DC test circuit ma V IH V DD V Input voltage V IL V pulse width t w V DD = V ns 1. The output current keep constant in range of mA if V OUT=1V. However, user can minimize V OUT to reduce power dissipation according to used current, e.g., set V OUT to 0.4V if I OUT=40mA. 2. The maximum Vout is package thermal limited, user should keep Vout under maximum power dissipation. Page 3 of 12

4 Electrical Characteristics (V DD =5V, T A =25 C unless otherwise noted) Characteristic Symbol Conditions Min. Typ. Max. Unit V IH V DD V Input voltage V IL V Output leakage I current OL V OUT = 24V ua Output current I OUT V OUT =1V =900I ma Current channel skew 1 di OUT1 V OUT =1V =900I 0 ±2 ±3 % Current chip skew 2 di OUT2 V OUT =1V =900I 0 ±4 ±6 % Line regulation 4.5V < V 3 %/dv DD < 5.5V I OUT vs. V DD DD =900I, V OUT > 1V Load regulation 1V < V 4 %/dv OUT < 4V, =900I, I OUT vs. V OUT OUT V DD =5V 0 ±0.5 ±1 %/V 0 ±0.5 ±1 %/V Pull0down resistor R DOWN KI Supply current OFF I DD(OFF)1 = Open, OUT 1 ~OUT 8 =OFF I DD(OFF)2 = 900N, OUT 1 ~OUT 8 =OFF ON I DD(ON) = 900N, OUT 1 ~OUT 8 =ON Channel skew=(i OUT0I AVG)/I AVG, where I AVG=(I OUT(max)+ I OUT(min))/2 2. Chip skew=(i AVG0I CEN) / I CEN*100(%), where I CEN is the statistics distribution center of output currents. 3. Line regulation=[i OUT(V DD=5.5V)0I OUT(V DD=4.5V)] / {[I OUT(V DD=5.5V)+I OUT(V DD=4.5V)]/2} / (5.5V04.5V)*100(%/V) 4. Load regulation=[i OUT(V OUT=4V)0I OUT(V OUT=1V)] / {[I OUT(V OUT=4V)+I OUT(V OUT=1V)]/2} / (4V01V)*100(%/V) Test Circuit for Electrical Characteristics ma V DD IDD C 1 =1uF ON OFF VDD REXT OUT1 OUT2 OUT8 I OUT V OUT C LED =10uF Page 4 of 12

5 Switching Characteristics (V DD =5V, T A =25 C unless otherwise noted) Characteristic Symbol Condition Min. Typ. Max. Unit Propagation delay time V DD = 5V 0 OUTn t ( L to H ) PLH = 5V ns V IH = V DD Propagation delay time 0 OUTn t ( H to L ) PHL V IL = ns = 900I Pulse width t w R L = 90I ns C Output rise time of I OUT t L = 10pF OR ns C 1 = 1uF Output fall time of I OUT t OF C LED = 10uF ns Test Circuit for Switching Characteristics V IH C 1 * V DD I DD VDD OUT1 I OUT V IL t R = t F = 10 ns OUT2 REXT OUT8 C L C LED * R L V OUT * Place the C1/CLED more close to IC VDD/OUT pin(not power supply) as possible. Timing Waveform 50% t PHL t W 50% t PLH OUTn 90% 50% 10% 50% 10% 90% t OF t OR Page 5 of 12

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 is shown as the following figure. I OUT vs. 150 IOUT(mA) 100 1V<V OUT<4V (KΩ) According to I0V curve, the output voltage should be larger than 1V to get 160 ma constant current. By applying proper output voltage, the output current set by an external resistor is approximate to: I OUT = 60(630 / REXT) (ma) (chip skew < ±6%). Thus the output current is set to be about 42mA at REXT = 900N. Output Characteristics The current characteristic of output curve is flat. The output current can be kept constant regardless of the variations of LED forward voltage when V OUT > V DO (drop0out voltage). The relationship between I OUT and V OUT is shown below. The output voltage should be kept as low as possible to prevent the from being overheated. 200 I OUT vs. V OUT 150 IOUT(mA) Drop-out voltage is current dependent, e.g. V DO=0.4V@I OUT=40mA V OUT(V) Page 6 of 12

7 Maximum Power Dissipation The maximum power dissipation (P D(max) ) of a semiconductor chip varies with different packages and ambient temperature. It s determined as P D(max) =(T J(max) T A )/R TH(j0a) where T J(max) : maximum chip junction temperature is usually considered as 150 C, T A : ambient temperature, R TH(j0a) : thermal resistance. Since P=IV, for sinking larger I OUT, users had better add proper voltage reducers on outputs to reduce the heat generated from the. 2.5 P D(max) vs. T A 2 SSOP16TP:R TH(j=a) = 60 C/W PD(max)(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) 0T A )/R TH(j0a) )0(V DD *I DD ))/V OUT /Duty/N, where T J(max) =150 C, N=8(all ON) I OUT(max) vs. O C/W 150 V OUT =4V V OUT =3V V OUT =2V V OUT =1V V OUT =3V V OUT =2V V OUT =1V I OUT(max) (ma) T A =85 C T A =25 C Duty(%) Page 7 of 12

8 Load Supply Voltage (VLED) The can be operated very well when V OUT ranges from 1V to 4V. However, 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 = 0V DROP 0V F. V DROP V DROP I OUT V F I OUT V F V OUT V OUT Page 8 of 12

9 Typical Application Circuits (1) Lighting with recommended =5V R DROP 10uF 101 R DROP OUT1= VDD REXT OUT5=8 SSOP16TP 1uF (2) Lighting with > 5V, e.g. =12V/24V Components suggestion: R 1 =( 0V Z )/(I DD +I Z ) If =24V, V Z =5.1V, I Z =1mA =900I, I DD(max) =15mA, then R DROP 10uF R DROP R 1 R 1 ~1.2K is obtained. Beware that: I DD is dependent, the higher the lower I DD, vice versa. R DROP =( 0n*V F 0V DO )/I OUT V DO is the drop0out voltage of intended output current. OUT1= SSOP16TP VDD REXT OUT5=8 V F ZD 1 ~5V C 1 C 1 =1uF (3) Lighting with dimming control 47uF R 1 ~5V C.U PWM Pulse OUT1= SSOP16TP VDD REXT OUT5=8 ZD 1 C 1 Page 9 of 12

10 PCB Design Considerations Use the following general guide0line when designing printed circuit boards (PCB) : Decoupling Capacitor Place a decoupling capacitor e.g. 1uF 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. Inadequate VDD decoupling can cause timing problems, and very noisy LED supplies can affect LED current regulation. V DD LPF 10N PWM dimming signal 10N 10pF 1/4.7uF VDD REXT C LED External Resistor ( ) 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 VDD and trace improves efficiency and ground bouncing by effect of reducing both power and ground parasitic resistance and inductance. A small value of resistor, e.g., 10N (higher if I OUT is larger) series in power input of the in conjunction with decoupling capacitor shunting the IC is recommended. Separating and feeding the LED power from another stable supply terminal, furthermore adding a capacitor C LED greater than 10uF beside the LED are recommended. Please adapt C LED according to total system current consumption. EMI Reduction To reduce the EMI radiation from system, an economical solution of RC low pass filter (LPF) is suggested to be used to lower the transient edge of PWM dimming signal, as shown in the figure above. Using at least four layers PCB board with two interior power and ground planes is a good scheme to decrease the signal current path which is the source of radiation emission. As a result, EMI radiation can be decreased. Page 10 of 12

11 Thermal Pad Consideration The thermal pad (also named as exposed pad ) SSOP16 package beneath is NOT directly wired to ground terminal (pin1) internally. User should be aware of this electrical connection when designing the PCB board. In most application, connecting the thermal pad to system ground is strongly suggested. In general, the heat generated from an IC is conducted to the PCB then radiates to the ambient. Thermal pad specifically increases the maximum power dissipation capability of the IC packages. To provide lower thermal resistance from the IC to the ambient air, PCB designers should layout larger thermal conduction areas on top layer (component side) and bottom layer as well as thermal vias, the more the better. In addition, connecting thermal via to the ground plane also increases thermal conduction areas, this improves the heat transfer efficiency at the same time greatly dissipates heat generated from the package. Furthermore, coating solder on bottom layer and selecting e.g. 2 oz. copper which will increase the total thickness of thermal conduction is an alternative. When making the solder paste screen, an opening should be created for the thermal pad. This way the thermal pad can be electrically and thermally connected to the PCB. As the thermal pad is soldered on copper polygon, the chance of inadvertently shorting the thermal pad to traces routed underneath it could be eliminated. Bonding Wire Die Thermal Pad Lead Frame Soldering Top Layer Thermal Conduction { PCB Ground Plane Power Plane Thermal Vias Heat Transfer Bottom Layer Thermal Conduction Multi0layers PCB Thermal conduction Thermal pad Thermal vias Page 11 of 12

12 Package Dimension SSOP16TP(check up0to0date version) D D2 c StarChips E1 Technology E2 E StarChips Technology Inc. L y c b e A1 A2 A SEATING PLANE 0.20 mm GAUGE PLANE θ Symbol Dimension (mm) Dimension (mil) Min. Nom. Max. Min. Nom. Max. A A A b c D E E D E e L y θ Revision History(check up0to0date version) Data Sheet Version V02_02 Remark Thermal pad description 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. StarChips Technology, Inc. 4F, No.5, Technology Rd.,ScienceBased Industrial Park, HsinChu,Taiwan, R.O.C. Tel: # 555 Page 12 of 12