RT9300A/B Tiny Package, Low Dropout Current Source General Description Features The RT9300A/B low-dropout bias supply for white LEDs is a high-performance alternative to the simple ballast resistors used in conventional white LED designs. The RT9300A/B uses an internal resistor to set the bias current for four LEDs, which are matched to 5%. The RT9300A/B's advantages over ballast resistors include much lower bias variation with supply voltage variation, significantly lower dropout voltage, and in some applications, significantly improved efficiency. The RT9300A/B requires only a 60/45mV dropout voltage at a 20/15mA load on each output to match the LED brightness. z Low 60/45mV Dropout at 20/15mA z 5% LED Current Matching Simple LED Brightness Control 2.5V to 5.5V Supply Voltage Range Thermal Shutdown Protection RoHS Compliant and 100% Lead (Pb)-Free z z z z Applications z z z z Next-Generation Wireless Handsets PDAs, Palmtops, and Handy Terminals Digital Cameras, Camcorders Battery-Powered Equipment Ordering Information RT9300A/B Pin Configurations Package Type E : SOT-23-6 (TOP VIEW) LED1 LED2 LED3 Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) 6 Sink Current A : 20mA B : 15mA 2 3 SOT-23-6 Richtek products are : Marking Information RoHS compliant and compatible with the current require- For marking information, contact our sales representative directly or through a Richtek distributor located in your area. ments of IPC/JEDEC J-STD-020. ` 4 EN GND LED4 Note : ` 5 Suitable for use in SnPb or Pb-free soldering processes. Typical Application Circuit VIN C 0.1uF 6 LED1 Enable 1 EN 5 LED2 4 LED3 3 LED4 RT9300A/B GND 2 Figure 1. Application Circuit for Backlight. DS9300A/B-05 April 2011 www.richtek.com 1 RT9300A/B VIN Keypad LED C 0.1uF 5 6 LED1 1 PWM LED2 4 LED3 3 LED4 RT9300A/B EN GND 2 Figure 2. Application Circuit for Keypad. Function Block Diagram LED2 LED4 LED1 LED3 EN Bandgap VREF + - UVLO Current Source OTP IREF Functional Pin Description Pin Name Function 1 EN Chip Enable (Active High). 2 GND Ground 3 LED4 LED4 Cathode Connection. Current flowing into LED4 is Constant. (20mA/15 mA) LED4 is High Impedance when EN is Low. 4 LED3 LED3 Cathode Connection. Current flowing into LED3 is Constant. (20mA/15 mA) LED3 is High Impedance when EN is Low. 5 LED2 LED2 Cathode Connection. Current flowing into LED2 is Constant. (20mA/15 mA) LED2 is High Impedance when EN is Low. 6 LED1 LED1 Cathode Connection. Current flowing into LED1 is Constant. (20mA/15 mA) LED1 is High Impedance when EN is Low. www.richtek.com 2 DS9300A/B-05 April 2011 RT9300A/B Absolute Maximum Ratings (Note 1) Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------The other pins -------------------------------------------------------------------------------------------------------------z Power Dissipation, PD @ TA = 25°C SOT-23-6 -------------------------------------------------------------------------------------------------------------------z Package Thermal Resistance (Note 2) SOT-23-6, θJA --------------------------------------------------------------------------------------------------------------z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------z Operation Temperature Range ----------------------------------------------------------------------------------------z Junction Temperature ----------------------------------------------------------------------------------------------------z Storage Temperature Range -------------------------------------------------------------------------------------------z ESD Susceptibility (Note 3) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) -----------------------------------------------------------------------------------------------------z z Recommended Operating Conditions z z −0.3V to 6V −0.3V to 6V 0.4W 250°C/W 260°C −40°C to 85°C 150°C −65°C to 150°C 2kV 200V (Note 4) Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C −40°C to 85°C Electrical Characteristics (VIN = 3.7V, TA = 25°C, Unless Otherwise specification) Parameter Symbol Test Conditions Min Typ Max Unit 2.5 -- 5.5 V -- 2.1 -- V -- 100 -- mV RT9300A 18 20 22 RT9300B 13.5 15 16.5 ILED = 0 -- -- 600 ILED = 20mA -- 60 -- ILED = 15mA -- 45 -- -- -- 5 % System Supply Input Operation Voltage Range VEN Under Voltage Lock Out V(UVLO) Falling UVLO Hysteresis LED Sink Current Quiescent Current mA IEN LED Dropout Voltage LED Current Deviation Matching uA mV EN High-Level Input Voltage VEN_H 2.5 -- -- V EN Low-Level Input Voltage VEN_L -- -- 0.7 V OTP -- 170 -- °C OTP Hysteresis -- 10 -- °C -- -- 1 uA Shutdown Current DS9300A/B-05 April 2011 ISHDN VEN < 0.4V www.richtek.com 3 RT9300A/B Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. 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 remain possibility to affect device reliability. Note 2. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Floating connection or pull low to disable this function. www.richtek.com 4 DS9300A/B-05 April 2011 RT9300A/B Typical Operating Characteristics LEDCurrent Current vs. EN Voltage LED Voltage LED Current vs. Input Voltage 18 18 16 16 VIN = 3.7V 14 LED 1 LED 2 LED 3 LED 4 12 10 LED LED Current Current (mA) (mA) LED Current (mA) 14 8 6 4 12 10 8 6 4 2 2 0 0 2 2.5 3 3.5 4 4.5 5 1.5 1.75 2 2.25 2.5 2.75 3 3.25 Input Voltage (V) EN Voltage Voltage (V) EN (V) LED Current vs. Temperature ENCurrent Current vs. vs. EN EN Supply EN Supply Voltage Voltage 15.5 3.5 400 VIN = 3.5V 350 15.4 EN EN Current Current (uA) (uA) LED Current (mA) 300 15.3 15.2 250 200 150 100 15.1 50 15 0 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 1.5 2 2.5 3 3.5 4 Temperature (°C) ENSupply Supply Voltage Voltage (V) EN (V) EN Pin Dimming Operation EN Pin Shutdown Response 4.5 VEN = 0V to 3V (2V/Div) EN Pin Voltage LED Current EN Pin Voltage (2V/Div) (10mA/Div) LED Current Time (50us/Div) DS9300A/B-05 April 2011 (10mA/Div) Time (50us/Div) www.richtek.com 5 RT9300A/B Line Transient Response VIN = 3.2V to 3.7V Input Voltage LED Current (1V/Div) (25mA/Div) Time (100us/Div) www.richtek.com 6 DS9300A/B-05 April 2011 RT9300A/B Applications Information Enable Input EN powers the input of the RT9300A/B. This IC provides an under voltage lockout (UVLO) function to prevent it from unstable issue when startup. The UVLO threshold of input falling voltage is set at 2.1V typically with a hysteresis 0.1V.Drive EN high to enable the device; drive EN low to disable the device. When driven high, EN draws 350uA to power the IC. Driving EN low forces LED1, LED2, LED3, and LED4 into a high-impedance state. LED Current RT9300A/B provides a constant current for white LED. Figure 1 shows a typical application circuit for 4 white LEDs. Each channel supports up to 20mA/15mA current and regulates a constant current for uniform intensity. For keypad LED application, the all channels must be connected to LED as shown in Figure 2. In order to maintain LED constant current, the input voltage must provide the required LED forward voltage and current source dropout voltage. If the forward voltage of white LEDs is 3.3V, the input voltage should be higher than 3.4V to provide enough voltage headroom for maintaining constant brightness. LED Brightness Dimming Control For controlling the LED brightness, the RT9300A/B can perform the dimming control by applying a PWM signal to EN pin. When an external PWM signal is connected to the EN pin, brightness of white LED is adjusted by the duty cycle. The average LED current is proportional to the PWM signal duty cycle. The magnitude of the PWM signal must be higher than the minimum level of enable input high level, in order to let the dimming control perform correctly, the suggested PWM frequency range is 10kHz to 200Hz. Thermal Considerations For continuous operation, do not exceed absolute maximum operation junction temperature 125°C. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of DS9300A/B-05 April 2011 surroundings airflow and temperature difference between junction to ambient. The maximum power dissipation can be calculated by following formula : PD(MAX) = ( TJ(MAX) - TA ) / θJA Where T J(MAX) is the maximum operation junction temperature 125°C, TA is the ambient temperature and the θJA is the junction to ambient thermal resistance. For recommended operating conditions specification of RT9300, where T J(MAX) is the maximum junction temperature of the die (125°C) and TA is the maximum ambient temperature. The junction to ambient thermal resistance θ JA is layout dependent. For SOT-23-6 packages, the thermal resistance θJA is 250°C/W on the standard JEDEC 51-3 single-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula : PD(MAX) = (125°C − 25°C) / (250°C/W) = 0.4W for SOT-23-6 packages The maximum power dissipation depends on operating ambient temperature for fixed TJ(MAX) and thermal resistance θJA. For RT9300 packages, the Figure 1 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed. 500 Maximum Power Dissipation (mW) The RT9300A/B is a 4-Channel current source driver for white LEDs. Single Layer PCB 450 400 350 SOT-23-6 300 250 200 150 100 50 0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curves for RT9300 Packages www.richtek.com 7 RT9300A/B Layout Considerations For best performance, careful PCB layout is necessary. All peripheral components should be placed as close to the IC as possible. A short connection is highly recommended. The following guidelines should be strictly followed when designing a PCB layout for the RT9300A/ B. ` All the traces of LED and VIN running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. ` The capacitor should be placed close to the anodes of LEDs and connected to ground plane. ` The GND should be connected to a strong ground plane for heat sinking and noise protection. All the traces of LED and VIN running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. Battery The GND should be connected to a strong ground plane for heat sinking and noise protection. GND PWM LED1 LED2 LED3 6 5 4 1 2 3 EN GND LED4 Figure 2 www.richtek.com 8 DS9300A/B-05 April 2011 RT9300A/B Outline Dimension H D L C B b A A1 e Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.889 1.295 0.031 0.051 A1 0.000 0.152 0.000 0.006 B 1.397 1.803 0.055 0.071 b 0.250 0.560 0.010 0.022 C 2.591 2.997 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 SOT-23-6 Surface Mount Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. DS9300A/B-05 April 2011 www.richtek.com 9