RT9364 Preliminary 80mA 4-Channel Charge Pump White LED Driver with Low Dropout Current Source General Description Features The RT9364 is a high performance white LED driver. It integrates current sources and automatic mode selection charge pump. The part maintains the high efficiency by utilizing an x1/x1.5 fractional charge pump and low dropout current sources. The small equivalent x1 mode open loop resistance and ultra-low dropout voltage of current source extend the operating time of x1 mode and optimize the efficiency of Li-ion battery in white LED applications. z 85% Average Efficiency Over Battery Life z Support up to 4 White LEDs 80mV Typical Current Source Dropout Support up to 80mA Output Current 1% Typical LED Current Accuracy 0.7% Typical LED Current Matching Soft Start Function Auto Charge Pump Mode Selection 250kHz Fixed Frequency Oscillator Output Over Voltage Protection 16-Step Brightness Control Low Input Noise and EMI Low 0.3μ μA Shutdown Current RoHS Compliant and 100% Lead (Pb)-Free The RT9364 supports up to 4 white LEDs and regulates a constant current for uniform intensity. The part implements a 4-bit DAC for brightness control. Users can easily configure the LED current from 1.25mA to 20mA by a serial pulse. 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. The operating voltage range is 2.8V to 5.0V. Internal soft start circuitry effectively reduces the in-rush current while both start-up and mode transition. The load is disconnected from VIN while shutdown and the shutdown current is less than 1μA. RT9364 is available in a WQFN 3x3-16L package. z z z z z z z z z z z z Applications z z z Mobile Phone, DSC, MP3 White LED Backlighting LCD Display Supply Pin Configurations `RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. 2 C2P 3 C1P 4 LED1 12 LED2 11 LED3 GND 10 LED4 9 NC 5 6 7 8 EN RichTek Pb-free products are : C2N VIN Note : 1 PGND Operating Temperature Range P : Pb Free with Commercial Standard 16 15 14 13 C1N AGND Package Type QW : WQFN-16L 3x3 (W-Type) NC VNG RT9364 VOUT (TOP VIEW) Ordering Information WQFN-16L 3x3 `Suitable for use in SnPb or Pb-free soldering processes. `100% matte tin (Sn) plating. Marking Information For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail. DS9364-00 May 2006 www.richtek.com 1 RT9364 Preliminary Typical Application Circuit CFLY 1uF CFLY 1uF 1 4 7 + Li-ion Battery CIN 1uF 2 3 C1N C2P C2N C1P VIN Pulse Input 8 EN RT9364 14 VOUT 16 VNG 5 AGND COUT 1uF 13 LED1 LED2 12 LED3 11 LED4 10 PGND 6 Figure 1. For 4-WLEDs Application Circuit CFLY 1uF CFLY 1uF 1 4 C1P 7 + Li-ion Battery CIN 1uF 3 2 C1N C2P C2N VIN Pulse Input 8 EN 14 VOUT 16 RT9364 VNG 5 AGND COUT 1uF 13 LED1 LED2 12 LED3 11 LED4 10 PGND 6 Figure 2. For 3-WLEDs Application Circuit 30us < tREADY 0.5us < t HI EN Shutdown ILEDX 0 1 2 3 3ms < tSHDN 0.5us < tLO < 500us 4 5 15 14 100% 15/16 14/16 13/16 12/16 3/16 0 1 100% 15/16 2/16 1/16 Shutdown Figure 3. Brightness control by pulse dimming www.richtek.com 2 DS9364-00 May 2006 RT9364 Preliminary Functional Pin Description Pin Number Pin Name Pin Function 1 C1N Negative Terminal of Bucket Capacitor 1. 2 C2N Negative Terminal of Bucket Capacitor 2. 3 C2P Positive Terminal of Bucket Capacitor 2. 4 C1P Positive Terminal of Bucket Capacitor 1. 5 AGND Analog Ground. 6 PGND Power Ground. 7 VIN Power Input Voltage. 8 EN Chip Enable (Active High), and connects to GPIO pin of MCU. 9, 15 NC No Internal Connection. 10 LED 4 Current Sink for LED4. (If not in use, pin should be connected to GND) 11 LED 3 Current Sink for LED3. (If not in use, pin should be connected to VIN) 12 LED 2 Current Sink for LED2. (If not in use, pin should be connected to VIN) 13 LED 1 Current Sink for LED1. (If not in use, pin should be connected to VIN) 14 VOUT Output Voltage Source for LED1 to LED4. 16 VNG Charge Pump Output. Exposed Pad GND Exposed pad should be soldered to PCB board and connected to GND. Function Block Diagram C1P C1N C2P C2N VIN x1/x1.5 Charge Pump Gate Driver VOUT OVP VNG UVLO 16 Steps Pulse Dimming Controller Soft Start EN Shutdown Delay LED1 Low Dropout Current Source LED2 LED3 LED4 250kHz OSC GND DS9364-00 May 2006 www.richtek.com 3 RT9364 Preliminary Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Input Voltage -----------------------------------------------------------------------------------------------------Other I/O Pin Voltage ----------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WQFN-16L 3x3 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 4) WQFN-16L 3x3, θJA ------------------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 2) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions z z −0.3V to 6V −0.3V to 6V 1.47W 68°C/W 150°C 260°C −40°C to 150°C 2kV 200V (Note 3) Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.6V, VF = 3.4V, CIN = COUT = CFLY = 1μF (ESR = 30mΩ), ILED1 to 4 = 15mA, TA = 25°C, unless otherwise specification) Parameter Symbol Test Condition Min Typ Max Units 2.8 -- 5.0 V -- 2.2 -- V -- 200 -- mV VEN = 1.8V -- 1 -- uA Input Input Supply Voltage VIN Under-Voltage Lockout Threshold VUVLOH VIN Rising Under-Voltage Lockout Hysteresis EN Pull Low Current Quiescent of x1 Mode IQ_x1 x1 Mode, VIN = 5.5V, LED off -- 1 -- mA Shutdown Current ISHDN VEN = 0V, VIN = 5.5V -- 0.4 7 μA VTRAN VLED= 3.4V, ILED1to 4 = 15mA -- 3.5 -- V -- 200 -- mV Output x1 Mode to x1.5 Mode Transition Voltage Mode Transition Hystersis ILEDx Accuracy ILED-ERR 100% Setting, ILED1 to 4 -8 -- +8 % Current Matching ILED-LED-ERR 100% Setting, ILED1 to 4 -5 -- +5 % EN Low Time for Shut Down TSHDN 3 -- -- ms EN Low Time for Dimming TLO 0.5 -- 500 μs EN High Time for Dimming THI 0.5 -- -- μs Logic-High Voltage VIH 1.5 -- -- V Logic-Low Voltage VIL -- -- 0.4 V -- 250 -- kHz -- 5.5 -- V Enable EN Threshold Frequency Oscillator Frequency fOSC Protection Over Voltage Protection www.richtek.com 4 VOVP VIN − VOUT DS9364-00 May 2006 Preliminary RT9364 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. Devices are ESD sensitive. Handling precaution is highly recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. 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. DS9364-00 May 2006 www.richtek.com 5 RT9364 Preliminary Typical Operating Characteristics LED Current vs. Input Voltage Efficiency vs. Input Voltage 100 26 90 24 LED Current (mA) Efficiency (%) 80 70 60 50 40 30 22 20 LED2 LED4 LED1 LED3 18 16 14 20 12 10 LED Vf = 3.15V 2.8 3.2 3.6 4 4.4 4.8 5.2 LED Vf = 3.3V 10 0 2.8 5.6 3.2 3.6 23 23 22 22 21 20 ILED4 ILED2 ILED1 ILED3 17 5.2 5.6 21 20 19 18 ILED4 ILED2 ILED1 ILED3 17 VIN = 4.0V 16 VIN = 3.2V 16 -40 -25 -10 5 20 35 50 65 80 95 -40 -25 -10 5 20 35 50 65 80 95 Temperature (°C) Temperature (°C) x1.5 Mode Quiescent Current vs. Temperature x1 Mode Quiescent Current vs. Temperature 1.6 2.20 1.5 2.15 Quiescent Current (mA) Quiescent Current (mA) 4.8 x1.5 Mode LED Current vs. Temperature 24 LED Current (mA) LED Current (mA) x1 Mode LED Current vs. Temperature 24 18 4.4 Input Voltage (V) Input Voltage (V) 19 4 1.4 1.3 1.2 1.1 1 0.9 0.8 2.10 2.05 2.00 1.95 1.90 1.85 0.7 VIN = 5.5V VIN = 5.5V 1.80 0.6 -40 -25 -10 5 20 35 50 Temperature (°C) www.richtek.com 6 65 80 95 -40 -25 -10 5 20 35 50 65 80 95 Temperature (°C) DS9364-00 May 2006 RT9364 Preliminary Frequency vs. Temperature 270 0.14 265 260 0.12 Frequency (kHz) Shutdown Current (uA) Shutdown Current vs. Temperature 0.16 0.1 0.08 0.06 0.04 255 250 245 240 235 0.02 230 VIN = 5.0V VIN = 5.0V 0 -40 -25 -10 5 20 35 50 65 80 225 -40 95 -25 -10 5 20 35 50 65 80 95 Temperature (°C) Temperature (°C) x1 Mode Inrush Current Response x1.5 Mode Inrush Current Response C2P (2V/Div) VOUT (1V/Div) C2P (2V/Div) VOUT (1V/Div) EN (2V/Div) IIN (100mA/Div) EN (2V/Div) IIN (200mA/Div) VIN = 3.7V VIN = 3.2V Time (100μs/Div) Time (100μs/Div) x1 Mode Dimming Operation Ripple & Spike VIN (200mV/Div) EN (2V/Div) VOUT (1V/Div) C2P (2V/Div) I LED (10mA/Div) I IN (100mA/Div) VIN = 3.7V Time (25μs/Div) DS9364-00 May 2006 VIN = 3.2V Time (5μs/Div) www.richtek.com 7 RT9364 Preliminary Applications Information The RT9364 uses a fractional switched capacitor charge pump to power up to four white LEDs with a programmable current for uniform intensity. The part integrates current sources and automatic mode selection charge pump. It maintains the high efficiency by utilizing an x1/x1.5 fractional charge pump and current sources. The small equivalent x1 mode open loop resistance and ultra-low dropout voltage of current source extend the operating time of x1 mode and optimize the efficiency in white LED applications. Selecting Capacitors The input operating voltage range of the RT9364 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 rising voltage is set at 2.2V typically with a hysteresis 0.2V. To get the better performance of RT9364, the selection of peripherally appropriate capacitor and value is very important. These capacitors determine some parameters such as input/output ripple voltage, power efficiency, maximum supply current by charge pump, To reduce the input and output ripple effectively, the low ESR ceramic capacitors are recommended. 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. The flying capacitor C1 and C2 determine the supply current capability of the charge pump and to influence the overall efficiency of system. The lower value will improve efficiency, but it will limit the LED's current at low input voltage. For 4 X 20mA load over the entire input range of 2.8V to 5.5V, it is recommended to use a 1μF ceramic capacitor on the flying capacitor C1 & C2. Soft Start Brightness Control The RT9364 employs a soft start feature to limit the inrush current. The soft-start circuit prevents the excessive inrush current and input voltage droop. The soft-start clamps the input current over a typical period of 50μs. The RT9364 implements a pulse dimming method to control the brightness of white LEDs. Users can easily configure the LED current from 1.25mA to 20mA by a serial pulse. 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. The detail operation of brightness dimming is showed in the Figure 3. Input UVLO Mode Decision The RT9364 uses a smart mode selection method to decide the working mode for optimizing the efficiency. Mode decision circuit senses the output and LED voltage for up/down selection. The RT9364 automatically switches to x1.5 mode whenever the dropout condition is detected from the current source and returns to x1 mode whenever the dropout condition releases. Over Voltage Protection The RT9364 equips over voltage protection function. When LED is open, the voltage between input and output will be clamped at a certain voltage level. LED connection The RT9364 supports up to 4 white LEDs. The four LEDs are connected from VIN to pin 10, 11, 12 and 13 respectively. If the LED is not used, the LED pin should be connected to VIN directly. Figure 2 shows the connection for 3-WLEDs application, pin 10 is connected to VIN. www.richtek.com 8 DS9364-00 May 2006 RT9364 Preliminary Layout Consideration ` 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. ` 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. LED1 LED2 LED3 LED4 12 11 10 9 13 VOUT 14 8 EN 7 VIN GND 15 6 PGND 16 5 AGND 1 2 3 4 CP1 COUT VNG Output capacitor must be placed between VNG and VOUT to reduce noise coupling from charge pump to LEDs. Battery CIN CP2 ` The exposed pad, PGND, AGND must be soldered to a large ground plane for heat sinking and noise prevention. The through-hole vias located at the exposed pad is connected to ground plane of internal layer. Ground Plane CN2 A short connection is highly recommended. The following guidelines should be strictly followed when designing a PCB layout for the RT9364. All the traces of LED and VIN running from chip to LCM module should be shielded and isolated by ground plane . CN1 The RT9364 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, CFLY1, and CFLY2 near to VIN, VOUT, CP1, CN1, CP2, CN2, and GND pin respectively. CFLY2 The exposed pad, PGND, and AGND should be connected to a strong ground plane for heat sinking and noise prevention. CFLY1 The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. Figure 4 ` 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. ` 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. ` Output capacitor must be placed between VNG and VOUT to reduce noise coupling from charge pump to LEDs. DS9364-00 May 2006 www.richtek.com 9 RT9364 Preliminary Outline Dimension D SEE DETAIL A D2 L 1 E E2 e b A A1 1 1 2 2 DETAIL A Pin #1 ID and Tie Bar Mark Options A3 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 2.950 3.050 0.116 0.120 D2 1.300 1.750 0.051 0.069 E 2.950 3.050 0.116 0.120 E2 1.300 1.750 0.051 0.069 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 16L QFN 3x3 Package RICHTEK TECHNOLOGY CORP. RICHTEK TECHNOLOGY CORP. Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)89191466 Fax: (8862)89191465 Email: [email protected] www.richtek.com 10 DS9364-00 May 2006