RT9363 Smallest 60mA 3-Channel Charge Pump White LED Driver with Low Dropout Current Source General Description Features The RT9363 is a high efficiency and cost effective charge pump white LED driver. It supports up to 3 white LEDs with regulated constant current for uniform intensity. The RT9363 maintains the highest efficiency by utilizing a x1/x2 charge pump and low dropout current regulators. z User can easily configure each LED current up to 20mA by a pulse dimming control. The dimming of white LEDs current can be achieved by applying a pulse signal to the EN pin. There are totally 16 steps of current could be set by users. z z z z z z z z z z The operating voltage range is 2.8V to 5.0V. Internal soft start circuitry effectively reduces the inrush current while both start-up and mode transition. RT9363 also provides comprehensive protections such as short circuit protection. The load is disconnected from VIN while shutdown and the shutdown current is less than 10μA. z Applications z z z RT9363 is available in a TSOT-23-8 package (1.0mm max height). Very High Efficiency Over 80% of Battery Life Support up to 3 White LEDs Support up to 60mA Output Current 1% Typical LED Current Matching Soft Start Function Short Circuit Protection Function Auto Charge Pump Mode Selection 250kHz Fixed Frequency Oscillator Output Over Voltage Protection 16-Step Brightness Control Low Input Noise and EMI RoHS Compliant and 100% Lead (Pb)-Free Mobile Phone, DSC, MP3 White LED Backlighting LCD Display Supply Pin Configurations Richtek products are : ` EN CP 6 5 2 3 4 VIN Note : 7 GND Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) 8 LED3 Package Type J8 : TSOT-23-8 LED1 RT9363 VOUT (TOP VIEW) LED2 Ordering Information TSOT-23-8 RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. DS9363-03 April 2011 www.richtek.com 1 RT9363 Typical Application Circuit RS 10k Pulse input CS 100pF 4 VIN CIN 4.7uF + 2 6 VOUT COUT 1uF 3 EN GND 5 CP RT9363 7 LED1 LED2 8 LED3 CP 1uF 1 Figure 1. For 3-WLEDs Application Circuit RS 10k Pulse input CS 100pF 4 VIN CIN 4.7uF + 2 VOUT COUT 1uF 3 EN GND 6 5 CP 1uF CP RT9363 7 LED1 LED2 8 LED3 1 Figure 2. For 2-WLEDs Application Circuit 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) 2 VOUT Output Voltage Source for LED1~3. 3 GND Power Ground. 4 VIN Input Voltage. 5 CP Positive Terminal of Bucket Capacitor. 6 EN Active High Enable. And connects 10k resistor to GPIO pin of MCU. 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) www.richtek.com 2 DS9363-03 April 2011 RT9363 Function Block Diagram CP VIN VOUT Current Limitation Soft Start Circuit OVP + Gate Driver 250kHz OSC Mode Decision Current Bias Vr1 LED1 LED2 UVLO 16 Steps Pulse Dimming Controller EN GND DS9363-03 April 2011 EN Check Shutdown Delay LED3 Current Source www.richtek.com 3 RT9363 Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Input Voltage -----------------------------------------------------------------------------------------------------Other I/O Pin Voltages --------------------------------------------------------------------------------------------------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 z −0.3V to 6V −0.3V to 6V 0.455W 220°C/W 260°C 125°C −65°C to 150°C 2kV 200V (Note 4) Operation Voltage Range ----------------------------------------------------------------------------------------------- 2.8V to 5V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.7V, TA = 25°C, unless otherwise specified) Parameter Input Supply Voltage Symbol Test Conditions VIN Under Voltage Lockout Threshold VIN Rising Under Voltage Lockout Hysteresis Min 2.8 Typ -- Max 5.0 Unit V -- 2.2 -- V -- 100 -- mV LEDs Current ILED 100% Setting -- 20 -- mA Shutdown Current ISHDN EN = 0V, VIN = 3.6V -- 3 10 μA Quiescent Current IQ -- 1 -- mA ILED Accuracy ILED-ERR 100% Setting, ILED1~3 −8 -- +8 % ILED-LED-ERR 100% Setting, ILED1~3 −5 -- +5 % -- 3.6 -- V -- 250 -- kHz -- -- 250 mA Logic-High VIH 1.5 -- -- Logic-Low VIL -- -- 0.25 (Note 6) Current Matching (Note 7) x1 mode to x2 mode Transition Voltage (VIN Falling) VTRANS1X Oscillator Frequency F OSC Inrush Current IINRUSH EN Threshold Voltage EN Current (V IN connect to LED1~3) VLED = 3.4V, IOUT = 45mA ILED1 = ILED2 = ILED3 = 15mA VIN = 3.0V (x2 mode) V Logic-High IIH VIH = 1.8V, RS = 10kΩ -- 200 -- Logic-Low IIL VIL = GND -- 0.1 10 2 -- -- ms 0.1 -- 0.3 ms 150 -- 300 mA EN Low Time for Shutdown T SHDN EN Low Time for Dimming T LO Short Circuit Current EN = High, VIN = 3.6V, No Load μA (To be continued) www.richtek.com 4 DS9363-03 April 2011 RT9363 Parameter Symbol EN High Time for Dimming THI EN High Time for Holding THO Over Voltage Protection V OVP Test Conditions (Note 5) Open circuit at any LED that is programmed to be in the on state Min Typ Max Unit 0.1 -- 0.3 ms 0.1 -- -- ms -- 5.5 -- V 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 is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. EN High time after the dimming sequence has being completed. Note 6. ILED Accaracy = 100% x (ILED1/2/3 − 20mA). Note 7. Current Matching = (ILED(MAX/MIN) − ILED, AVG) / ILED, AVG. DS9363-03 April 2011 www.richtek.com 5 RT9363 Typical Operating Characteristics Efficiency vs. Input Voltage Efficiency vs. Input Voltage 100% 100 ILED = 15mA, VF = 3.12V 90% 90 90% 90 80% 80 80% 80 Efficiency (%) Efficiency (%) 100% 100 70% 70 60% 60 50% 50 40% 40 ILED = 20mA, VF = 3.12V 70% 70 60% 60 50% 50 40% 40 30 30% 30% 30 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6 2.8 3.2 3.6 Input Voltage (V) 4 4.4 4.8 5.2 5.6 Input Voltage (V) Input Current vs. Input Voltage LED Current vs. Input Voltage 23 130 VF = 3.13V TA = 25°C 120 22 Input Current (mA) LED Current (mA) 110 21 20 19 100 90 80 70 60 18 50 40 17 2.5 3 3.5 4 4.5 5 3 5.5 3.1 3.2 Input Voltage (V) x1 Mode LED Current vs. Temperature 3.4 3.5 3.6 3.7 x2 Mode LED Current vs. Temperature 22 22 21 21 20 LED1 LED3 19 LED2 18 17 LED Current (mA) LED Current (mA) 3.3 Input Voltage (V) 20 LED1 19 LED3 LED2 18 17 16 16 -40 -20 0 20 40 Temperature (°C) www.richtek.com 6 60 80 100 -40 -20 0 20 40 60 80 100 Temperature (°C) DS9363-03 April 2011 RT9363 Shutdown Current vs. Temperature Quiescent Current vs. Temperature 4.5 0.98 VIN = 3.6V 0.97 Quiescent Current (mA) Shutdown Current (uA) 4 3.5 3 2.5 2 0.96 0.95 0.94 0.93 0.92 0.91 0.9 1.5 0.89 -40 -25 -10 5 20 35 50 65 80 95 -40 -25 -10 5 Temperature (°C) 1.2 4.5 1.1 4 Quiescent Current (mA) Quiescent Current (mA) 35 50 65 80 95 x2 Mode Quiescent Current vs. Input Voltage x1 Mode Quiescent Current vs. Input Voltage 1 0.9 0.8 0.7 0.6 0.5 3.5 3 2.5 2 1.5 1 0.4 2.5 3 3.5 4 4.5 5 2.5 5.5 3 3.5 4.5 5 5.5 Mode Transition Hysteresis vs. Temperature Input Voltage vs. Temperature Mode Transition Hysteresis (mV)1 2.25 POR 2.20 2.15 POF 2.10 4 Input Voltage (V) Input Voltage (V) Input Voltage (V) 20 Temperature (°C) 2.05 2.00 1.95 360 x2 Mode, VIN = 3.3V 340 320 300 280 260 240 220 200 -40 -20 0 20 40 60 Temperature (°C) DS9363-03 April 2011 80 100 -40 -20 0 20 40 60 80 100 Temperature (°C) www.richtek.com 7 RT9363 x1 Mode Inrush Current OVP 5.62 5.61 CP (2V/Div) VOUT (500mV/Div) 5.6 OVP (V) 5.59 5.58 5.57 5.56 EN (1V/Div) I IN (100mA/Div) 5.55 5.54 VIN = 3.7V 5.53 2.8 3.3 3.8 4.3 4.8 5.3 5.8 Time (100μs/Div) Input Voltage (V) x2 Mode Mode Inrush Current x1 Mode Normal Operation VIN (200mV/Div) VOUT (500mV/Div) CP (2V/Div) VOUT (500mV/Div) CP (2V/Div) EN (1V/Div) I IN (100mA/Div) VIN = 3.2V I LED (20mA/Div) Time (100μs/Div) Time (10μs/Div) x2 Mode Normal Operation Ripple & Spike VIN (200mV/Div) VOUT (500mV/Div) VIN ac (100mV/Div) VOUT (500mV/Div) CP (2V/Div) CP (2V/Div) I IN (100mA/Div) I IN (100mA/Div) VIN = 3.2V Time (10μs/Div) www.richtek.com 8 VIN = 3.7V VIN = 3.2V Time (5μs/Div) DS9363-03 April 2011 RT9363 Application Information High Efficiency x1/x2 Charge Pump Before the discussion of efficiency in RT9363, two things need to be illustrated. One is the Li-ion battery life time, the other is the forward voltage of white LED. The Li-ion battery energy is not linearly proportion to battery voltage. In the Figure 3, It shows the 80% battery life of Liion is arranged in 3.65V to 4.0V. The other voltage range occupies less than 20% battery energy and is insignificant. In the backlight application, the forward voltage of white LEDs most likely falls in 3.2 to 3.5V @ILED = 20mA. The development concept of RT9363 is based on the backlight application with Li-ion battery. RT9363 is very cost-effective product for driving white LEDs in backlight. It extends the 80% battery life by the reduction of open loop resistance at x1 mode and current source drop out voltage. Figure 4 is the efficiency diagram of RT9363, 80% battery life is marked by red rectangle. The RT9363 maximize the x1 mode operating range in the 80% battery life. Therefore, the efficiency is not significant different to that without x1.5 mode charge pump. The peak efficiency of RT9363 is 93% and average is 84%. Comparing to the LED drivers with x1.5 mode, only 1 to 2% efficiency loss by x2 mode. (Assume 5% battery life in charge pump mode and the efficiency difference of x1.5 and x2 modes is 25%, the efficiency loss thus is 5%x25% = 1.25%) Battery Voltage (V) 80% Battery Life 4.2 4.0 3.65 Capacity (mAH) 50 650 Figure 3. Li-ion Battery Energy Capacity Versus Battery Voltage. DS9363-03 April 2011 LED Efficiency vs. VIN 100 90 Efficiency (%) The RT9363 is a high efficiency charge pump white LED driver. It provides low drop-out voltage current source to regulate 3 white LEDs current. For high efficiency, the RT9363 implements x1/x2 mode charge pump with auto mode selection. In the application with Li-ion battery, it provides a very cost-effective and high efficiency solution for driving white LEDs. 80 70 60 50 40 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 VIN (V) Figure 4. Efficiency of RT9363. (ILED = 60mA, VF = 3.45V) Soft Start The RT9363 includes a soft start circuit to limit the inrush current at power on and mode switching. Soft start circuit holds the input current level long enough for output capacitor COUT reaching a desired voltage level. When the soft start is turning off, the RT9363 will not sink spike current from V IN. Mode Decision The RT9363 uses a smart mode decision method to select the working mode for maximum efficiency. Mode decision circuit senses the output and LED voltage for up/down selection. Dimming Control RT9363 implements the pulse dimming method being used to control the brightness of white LEDs. There are 16 steps to set the current of white LEDs. The maximum LED current is up to 20mA that is sufficient for most application in backlight. The detail operation of brightness dimming is showed in the Figure 5. At the beginning, the output current is set at 100% for step 0. In every step change, the output current will be reduced in 1/16 level from 16/16 until it reaches the minimum value of 1/16. After it reaches the value of 1/16, it will start a whole new cycle from 100% for continuous step changes. www.richtek.com 9 RT9363 The GPIO signal determines the step changes. For a step change, the duration of Logic Low signal must be within the range of 0.1ms to 0.3ms. When the signal changes from Low to High, it will trigger a step change to reduce output current in 1/16 level. When the signal remains at Logic High, the output current will be held and stays at the same step. Finally, when the signal stays longer than 2ms Logic Low, the chip will shut down the output current. Table 1 shows the corresponding dimming current for each step. 0.1ms < tHO 0.1ms < tHI 0.1ms < tLO < 0.3ms the output ripple, increasing the output capacitance COUT is necessary. However, this will increase the start-up time of output voltage. For LED driver applications, the input voltage ripple is more important than output ripple. Input ripple is controlled by input capacitor CIN, increasing the value of input capacitance can further reduce the ripple. Practically, the input voltage ripple depends on the power supply impedance. Tantalum capacitors are not recommended for use with the RT9363. So tantalum capacitor values and ceramic capacitor values can use the same. But COUT can set tantalum capacitor; because during the charge pump is x2 mode the VOUT is negative voltage. 2ms < tSHDN PCB Board Layout 0 Shutdown 1 2 3 4 5 14 100% 15/16 14/16 13/16 12/16 3/16 0 15 1 100% 2/16 2/16 15/16 1/16 Shutdown Figure 5. Brightness control by pulse dimming. RT9363 implements 16 steps brightness control Table 1. The Output Current Setting of 16 Steps Step Output (mA/CH) 0 20 1 18.75 2 17.5 3 16.25 4 15 5 13.75 6 12.5 7 11.25 Step Output (mA/CH) 8 10 9 8.75 10 7.5 11 6.25 12 5 13 3.75 14 2.5 15 1.25 The RT9363 is a high-frequency switched-capacitor converter. Careful PCB layout is necessary. For best performance, place all peripheral components as close to the IC as possible. Place CIN, COUT, and CP near to VIN, VOUT, CP, EN, and GND pin respectively. A short connection is highly recommended. The following guidelines should be strictly followed when designing a PCB layout for the RT9363. z The GND must be soldered to a large ground plane for heat sinking and noise prevention. The through-hole vias located under IC is connected to ground plane of internal layer. z VIN traces should be wide to minimize inductance and handle the high currents. The trace running from battery to chip should be placed carefully and shielded strictly. The anodes of LEDs must connect to CIN, not battery directly. z Input and output capacitors must be placed close to the part. The connection between pins and capacitor pads should be copper traces without any through-hole via connection. z The flying capacitors must be placed close to the part. The traces running from the pins to the capacitor pads should be as wide as possible. Long traces will also produce large noise radiation caused by the large dv/dt on these pins. Short trace is recommended. z All the traces of LED and VIN running from pins to LCM module should be shielded and isolated by ground plane. The shielding prevents the interference of high frequency noise coupled from the charge pump. Short Circuit Protection A current limiting circuit is also included in the RT9363 for short circuit protection. Whenever output is shorted to GND and source a dangerously high current, the current limiting circuit takes over the output regulation circuit and reduces the output current at an acceptable level. Selecting Capacitors To get the better performance of RT9363, the selecting of peripherally appropriate capacitor and value is very important. These capacitors determine some parameters such as input and output ripple, power efficiency, maximum supply current by charge pump, and start-up time. To reduce the input and output ripple effectively, the low ESR ceramic capacitors are recommended. Generally, to reduce www.richtek.com 10 DS9363-03 April 2011 RT9363 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. COUT All the traces of LED and VIN running from chip to LEDs should be wide and short to reduce the parasitic connection resistance and shielded, isolated by ground plane . LED3 1 8 LED2 VOUT 2 7 LED1 GND 3 6 EN GPIO Output capacitor (COUT) should be placed close to VOUT and connected to ground plane. RS CP Battery VIN 4 5 CP CS CIN Ground Plane The GND should be connected The traces running from pins to flying capacitor to a strong ground plane for heat should be short and wide to reduce parasitic resistance and prevent noise radiation. Long sinking and noise protection. parallel traces of EN and LED1 should be prevented to reduce the noise coupling from EN to LED1. Figure 6. PCB Layout Guide. Figure 7. PCB Layout Top Layer. Figure 8. PCB Layout Bottom Layer. DS9363-03 April 2011 www.richtek.com 11 RT9363 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. www.richtek.com 12 DS9363-03 April 2011