RT9302 60mA 3-Channel Pulse Dimming Current Source LED Driver General Description Features The RT9302 is a high performance constant current driver for white LED. It supports up to 3 white LEDs and regulates a constant current for uniform intensity. Each channel supports up to 20mA output current with 1% typical current accuracy and 0.7% typical current matching. The RT9302 provides a 16-step brightness dimming control. The LED current can be easily configured from 1.25mA to 20mA. The dimming of white LEDs' current can be achieved by applying a pulse signal to the EN pin. The LED current can be turned off by EN pin with pull low for 20μs or longer. The typical leakage current is 4μA while shutdown z Support Up to 3 White LEDs z Output Current up to 20mA Each Channel Support Pulse and PWM Dimming 40mV Typical Current Source Dropout 1% Typical LED Current Accuracy 0.7% Typical LED Current Matching 16-Step Brightness Control Low Noise and EMI Low Shutdown Current 4μ μA Typical RoHS Compliant and 100% Lead (Pb)-Free condition. Applications RT9302 is available in a TSOT-23-8 package (1.0mm maximum height). z z z z z z z z z z z Mobile Phone, DSC, MP3 White LED Backlighting LCD Display Supply Ordering Information Pin Configurations LED1 EN NC 8 7 6 5 2 3 4 GND VIN Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) (TOP VIEW) NC Package Type J8 : TSOT-23-8 LED2 RT9302 Note : ` RoHS compliant and compatible with the current require- ` Suitable for use in SnPb or Pb-free soldering processes. ments of IPC/JEDEC J-STD-020. LED3 Richtek products are : TSOT-23-8 Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. DS9302-04 April 2011 www.richtek.com 1 RT9302 Typical Application Circuit VIN 2.8 to 5.5V 4 VIN CIN 4.7uF RT9302 6 3 LED1 EN GND 7 LED2 8 LED3 1 Figure 1. For 3-WLEDs Application Circuit VIN 2.8 to 5.5V 4 VIN CIN 4.7uF RT9302 6 3 LED1 EN GND 7 LED2 8 LED3 1 Figure 2. For 2-WLEDs Application Circuit 0.5us < tHI EN 0 1 100% Shutdown ILEDx 20us < tSHDN 0.5us < tLO < 10us 2 3 4 5 15/16 14/16 13/16 12/16 0 15 14 1 100% 3/16 2/16 1/16 15/16 Shutdown Figure 3. Brightness control by pulse dimming. RT9302 implements 16 steps brightness control www.richtek.com 2 DS9302-04 April 2011 RT9302 Functional Pin Description Pin Number Pin Name Pin Function 1 LED3 Current Sink for LED3. (If not in use, this pin must be connected to VIN) NC No Internal Connection. 3 GND Power Ground. 4 VIN Input Voltage. 6 EN Chip Enable. 7 LED1 Current Sink for LED1. (If not in use, this pin must be connected to VIN) 8 LED2 Current Sink for LED2. (If not in use, this pin must be connected to VIN) 2, 5 Function Block Diagram EN 16 steps Pulse Dimming Controller 1MHz Oscillator Shut Down Delay Low Dropout Current Source UVLO GND VIN DS9302-04 April 2011 LED1 LED2 LED3 www.richtek.com 3 RT9302 Absolute Maximum Ratings z z z z z z z z z (Note 1) Supply Input Voltage -----------------------------------------------------------------------------------------------------Other I/O Pin Voltages --------------------------------------------------------------------------------------------------VIN, EN to GND -----------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C TSOT-23-8 ------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) TSOT-23-8, θJA ------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions z z −0.3V to 6V −0.3V to 6V 6V 0.455W 220°C/W 260°C 150°C −65°C to 150°C 2kV 200V (Note 4) Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.6V, CIN = 1uF, ESR = 0.03Ω, VF = 3.4V, ILED1 = ILED2 = ILED3 = 20mA, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit 2.8 -- 5.5 V -- 2.0 -- V -- 200 -- mV Input Input Supply Voltage VIN Under Voltage Lockout Threshold VIN falling Under Voltage Lockout Hysteresis Shutdown Current ISHDN VEN = 0V -- 4 10 μA Quiescent Current IQ VEN = High, IOUT = 0 -- 0.4 -- mA Output Current ILED 100% setting, VLED = 1V 18.4 20 21.6 mA Current Matching ILED-LED 100% setting, VLED = 1V −5 0 +5 % Dropout Voltage VLED 90% of full output current -- 40 150 mV Logic-High VIH 1.5 -- -- Logic-Low VIL -- -- 0.4 0.5 -- -- 0.5 -- 10 10 16 20 μs -- 1 -- μA Output Enable EN Threshold Voltage Shutdown Delay TSHDN Duration of EN Logic High for pulse dimming Duration of EN Logic Low for pulse dimming From EN Low to Shutdown EN Input Current IEN VEN = 1.8V Logic-High T HI Time of EN Logic Logic-Low T LO www.richtek.com 4 V μs DS9302-04 April 2011 RT9302 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 T A = 25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution recommended. Note 4. The device is not guaranteed to function outside its operating conditions. DS9302-04 April 2011 www.richtek.com 5 RT9302 Typical Operating Characteristics Shutdown Current vs. Input Voltage Quiescent Current vs. Input Voltage 9 0.44 -40°C 25°C 7 6 85°C 5 4 3 2 0.43 Quiescent Current (mA) Shutdown Current (uA) 8 -40°C 25°C 0.42 0.41 85°C 0.4 0.39 0.38 0.37 1 0 0.36 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 2.6 2.8 Input Voltage (V) 5 5.2 Input Voltage (V) LED Current vs. Input Voltage LED Current vs. Temperature 22 25 21.5 22.5 LED1 VF = 3.124V LED2 VF = 3.224V 20 LED Current (mA) 21 LED Current (mA) 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 20.5 20 19.5 19 18.5 17.5 LED3 VF = 3.143V 15 12.5 10 7.5 18 5 17.5 2.5 0 17 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 2.7 2.95 3.2 3.45 3.7 3.95 4.2 4.45 4.7 4.95 5.2 Input Voltage (V) Temperature (°C) Dimming Operation Dimming Operation EN (5V/Div) EN (2V/Div) I LED (5mA/Div) I LED (5mA/Div) Time (25μs/Div) www.richtek.com 6 VIN = 3.7V VIN = 3.7V Time (100μs/Div) DS9302-04 April 2011 RT9302 Turn-On Dimming Operation EN (2V/Div) EN (2V/Div) I IN (50mA/Div) I LED (10mA/Div) I LED (5mA/Div) VIN = 3.7V VIN = 3.7V Time (5μs/Div) Time (10μs/Div) Turn-Off EN (2V/Div) I IN (50mA/Div) I LED (10mA/Div) VIN = 3.7V Time (5μs/Div) DS9302-04 April 2011 www.richtek.com 7 RT9302 Application Information Input UVLO The input operating voltage range of the RT9302 is 2.8V to 5.5V. An input capacitor at the VIN pin could reduce ripple voltage. It is recommended to use a ceramic 1μF or larger capacitance as the input capacitor. 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 2V typically with a hysteresis 0.2V. Output Current RT9302 provides a constant output current for white LED. Figure 1 shows a typical application circuit for 3 white LEDs. Each channel supports up to 20mA output current and regulates a constant current for uniform intensity. For two or one LED application, the non-used channel must be connected to VIN as shown in Figure 2. Brightness Dimming Control The RT9302 provides a 16-step brightness dimming control. The LED current can be easily configured from 1.25mA to 20mA. The dimming of white LEDs' current can be achieved by applying a pulse signal to the EN pin. Figure 3 shows the configuration of the 16-step pulse dimming control operation. The output current is set at 100% of 20mA typical output current when EN pin pull high initially from shutdown condition. The step change of pulse dimming can be implemented by EN pin changing with a logic Low pulse. Each step change 1/16 of full output current setting. The output current change of pulse dimming is designed in decreasing sequence in terms of (16/16, 15/16, ....., 1/16) and then (16/16, 15/16, .....) cycle by cycle. The duration of logic Low pulse is between 0.5us and 10μs. The duration of EN logic High pulse should be longer than 0.5μs. the IC as possible. A short connection is highly recommended. The following guidelines should be strictly followed when designing a PCB layout for the RT9302. 1. All the traces of LED and VIN running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. 2. Input capacitor (CIN) should be placed close to VIN and connected to ground plane. The anodes of LEDs must be connected to CIN, not battery directly. 3. 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. Input capacitor (CIN) should be placed close to VIN and connected to ground plane. The Anodes of LEDs must connect to CIN, not battery directly. Battery CIN LED3 1 8 LED2 NC 2 7 LED1 GND 3 6 EN VIN 4 5 NC GPIO Ground Plane The GND should be connected to a strong ground plane for heat sinking and noise protection. Figure 4. PCB Layout Guide The LED current can be turned off by EN pin with pulling low for 20μs or longer. The typical leakage current is 4μA while shutdown condition. Layout Consideration For best performance, careful PCB layout is necessary. All peripheral components should be placed as close to www.richtek.com 8 DS9302-04 April 2011 RT9302 Outline Dimension H D L C B b A A1 e Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.220 0.380 0.009 0.015 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.585 0.715 0.023 0.028 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 TSOT-23-8 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. DS9302-04 April 2011 www.richtek.com 9