RT9363A. 3 Channels 90mA x1/x2 Charge Pump White LED Driver. General Description. Features. Applications

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1 Channels 90mA x/x Charge Pump White LED Driver General Description The is a compact, high efficient and highly integrated charge pump white LED driver. It maintains the highest efficiency by utilizing a x/x fractional charge pump and low dropout current regulators. The supports up to white LEDs and regulates a constant current for uniform intensity. The part implements a -bit DAC for brightness control. Users can select external R SET or internal R SET by ISET pin. The dimming of white LEDs' current can be achieved by applying a pulse signal to the pin. There are totally 6 steps of current could be set by users. The part can support 5mA to 0mA for the 00% current setting. Users also can use the internal R SET for 00% current setting of 0mA just by connecting the ISET pin to V IN. The operating voltage range is from.v to 5.5V. Internal soft start circuitry effectively reduces the inrush current while both start-up and mode transition. The load is disconnected from V IN while shutdown and the shutdown current is less than ua. is available in a WDFN -0L x package. Ordering Information Package Type QW : WDFN-0L x (W-Type) Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) Note : Richtek products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-00. Suitable for use in SnPb or Pb-free soldering processes. Features Over 0% Average Efficiency Over Battery Life Support Up to White LEDs 0mV Typical Current Source Dropout Support Up to 90mA Output Current % Typical LED Current Accuracy 0.% Typical LED Current Matching Soft Start Function Automatic Charge Pump Mode Selection MHz Random Frequency Oscillator Over Voltage Protection 6-Step Brightness Control Low Input Noise and EMI Low ua Shutdown Current Flexible Current Setting RoHS Compliant and 00% Lead (Pb)-Free Applications Mobile Phone, DSC, MP White LED Backlighting LCD Display Supply Pin Configurations CP (TOP VIEW) WDFN-0L x 9 ISET Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. DS96A-0 April 0

2 Typical Application Circuit Li-ion Battery + C IN.uF GPIO CP 5 9 ISET 0 6 C FLY uf C OUT.uF Figure. Internal R SET(MAX) = 0mA, for -WLEDs Application Circuit Li-ion Battery + C IN.uF GPIO CP 5 9 ISET 0 6 C FLY uf C OUT.uF Figure. Internal R SET(MAX) = 0mA, for -WLEDs Application Circuit Li-ion Battery + C IN.uF GPIO R SET CP 5 9 ISET 0 6 C FLY uf C OUT.uF Figure. External R SET(MAX) = 5 to 0mA, for -WLEDs Application Circuit Li-ion Battery + C IN.uF GPIO R SET CP 5 9 ISET 0 6 C FLY uf C OUT.uF Figure. External R SET(MAX) = 5 to 0mA, for -WLEDs Application Circuit DS96A-0 April 0

3 Timing Diagram 0us < T READY 0.5us < T HI 0.5us < T LO < 500us ms < T SHDN Shutdown ILEDX % 5/6 00% /6 5/6 /6 /6 /6 /6 Shutdown Figure 5. Pulse Dimming Waveform Functional Pin Description Pin No. Pin Name Pin Function Current Sink for. (If not in use, this pin must be connected to V IN ). Current Sink for. (If not in use, this pin must be connected to V IN ). Current Sink for. (If not in use, this pin must be connected to V IN ). Negative Terminal of Bucket Capacitor. 5 CP Positive Terminal of Bucket Capacitor. 6, (Exposed Pad) Ground. The exposed pad must be soldered to a large PCB and connected to for maximum power dissipation. Input Voltage. Output Voltage Source for ~. 9 ISET LED Current Adjust Input. 0 Chip Enable (Active High). DS96A-0 April 0

4 Function Block Diagram CP OVP Soft Start Circuit Gate Driver MHz OSC + - Vr Mode Decision UVLO 6 Steps Pulse Dimming Controller Current Bias Min VDS ISET Shutdown Delay Current Source R SET R SET Selection DS96A-0 April 0

5 Absolute Maximum Ratings (Note ) Electrical Characteristics Supply Input Voltage V to 6V Output Voltages V to 6V Power Dissipation, P T A = 5 C WDFN 0L x W Package Thermal Resistance (Note ) WDFN 0L x, θ JA C/W WDFN 0L x, θ JC C/W Junction Temperature C Lead Temperature (Soldering, 0 sec.) C Storage Temperature Range C to 50 C ESD Susceptibility (Note ) HBM (Human Body Mode) kv MM (Machine Mode) V Recommended Operating Conditions (Note ) Junction Temperature Range C to 5 C Ambient Temperature Range C to 5 C (V IN =.6V, C IN = C OUT =.uf, C FLY = uf, V F =.5V, I = I = I = 0mA, ESR = 0.0Ω, TA = 5 C, unless otherwise specified). Input Power Supply Parameter Symbol Test Conditions Min Typ Max Unit Input Supply Voltage V IN V V UVLO_R V Under Voltage Lockout Threshold VUVLO_F mv Quiescent Current of x Mode I Qx x Mode(~ connect to V IN ) ma Quiescent Current of x Mode I Qx X Mode No Load ma Shutdown Current I SHDN = 0V, V IN = 5V -- ua LED Current I LED Accuracy I LED-ERR 00% Setting -- + % Current Matching I LED-LED-ERR 00% Setting % Charge Pump Oscillator Frequency F OSC khz x mode to x mode Transition Voltage Protection V TS V F =.5V, I OUT = 60mA V IN Falling V Over Voltage Protection V OVP Open Circuit at any LED Pin V To be continued DS96A-0 April 0 5

6 Digital Input Parameter Symbol Test Conditions Min Typ Max Unit Threshold Voltage Current Logic-High V _H Logic-Low V _L Logic-High I _H V = V IN -- Logic-Low I _L V = 0V V ua Low to Shutdown Delay T SHDN Refer to Figure ms High Time for Dimming T HI Refer to Figure us High Time for Holding T LO Refer to Figure us Note. 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. θja is measured in the natural convection at TA = 5 C on the high effective thermal conductivity four layers thermal test board of JEDEC 5- thermal measurement standard. The case point of θjc is on the expose pad. Note. Devices are ESD sensitive. Handling precaution is recommended. Note. The device is not guaranteed to function outside its operating conditions. 6 DS96A-0 April 0

7 Typical Operating Characteristics Efficiency (%) Efficiency vs. Input Voltage LED Vf =.V Input Voltage (V) LED Current (ma) LED Current vs. Input Voltage LED Vf =.V Input Voltage (V) x Mode LED Current vs. Temperature x Mode LED Current vs. Temperature LED Current (ma) 0 9 LED Current (ma) 0 9 =.0V =.V Quiescent Current (ma) x Mode Quiescent Current vs. Temperature =.5V Quiescent Current (ma) x Mode Quiescent Current vs. Temperature =.5V DS96A-0 April 0

8 Shutdown Current (ua) Shutdown Current vs. Temperature =.5V Frequency (khz) Frequency vs. Temperature =.5V x Mode Inrush Current Response x Mode Inrush Current Response (5V/Div) V OUT (V/Div) (V/Div) (5V/Div) V OUT (V/Div) (V/Div) IIN (00mA/Div) IIN (00mA/Div) =.V =.V Time (50us/Div) Time (50us/Div) x Mode Dimming Operation x Mode Ripple Voltage V IN (50mV/Div) (V/Div) V OUT (50mV/Div) (V/Div) ILED (0mA/Div) =.V ILED (0mA/Div) =.V Time (5ms/Div) Time (.5us/Div) DS96A-0 April 0

9 Application information The uses a fractional switched capacitor charge pump to power up to three white LEDs with a programmable current. The part integrates current sources and automatic mode selection charge pump. It maintains the high efficiency by utilizing an x/x fractional charge pump and current sources. The small equivalent x mode open loop resistance and ultra-low dropout voltage of current source extend the operating time of x mode and optimize the efficiency in white LED applications. The operating voltage range is from.v to 5.5V. Internal soft start circuitry effectively reduces the in-rush current while both start-up and mode transition. The load is disconnected from V IN while shutdown and the shutdown current is less than ua. High Efficiency x/x Charge Pump Before the discussion of efficiency in, 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 6, It shows the 0% battery life of Li-ion is arranged from.65v to.0v. The other voltage range occupies less than 0% battery energy and is insignificant. In the backlight application, the forward voltage of white LEDs most likely falls in. LED = 0mA. The developing concept of RT96 is based on the backlight application with Li-ion battery. is very cost-effective product for white LEDs backlight driving. It extends the 0% battery life by the reduction of open loop resistance at x mode and current source drop out voltage. Figure is the efficiency diagram of RT96 and 0% battery life is marked by red rectangle. The maximize the x mode operating range in the 0% battery life. Therefore, the efficiency is not significant different to that without x.5 mode charge pump. The peak efficiency of is 9% and the average is %. Comparing to the LED drivers with x.5 mode, only to % efficiency loss by x mode. (Assume 5% battery life in charge pump mode and the efficiency difference of x.5 and x modes is 5%, the efficiency loss thus is 5%x5% =.5%). Protection The includes a soft start circuit to limit the inrush current at power on and mode transition. Soft start circuit holds the input current level long enough for output capacitor C OUT reaching a desired voltage level. When the soft start off, the won't sink spike current from V IN. An over voltage protection function protect the output voltage from dangerous high voltage. The OVP turns off charge pump when the voltage difference between V IN and V OUT is over the designed target. LED Current Setting In Backlighting part, an internal R SET is used to set the initial current (0mA) of white LED and implements a -bit DAC for brightness control. Users can easily configure the LED current by a serial pulse. The dimming of white LEDs' current can be achieved by applying a pulse signal to the pin. There are totally 6 steps of current could be set by users. An automatic R SET selection is implemented in this part. can automatically select the internal or external R SETs by the connection of ISET pin. The LED current can be calculated by the following equation. SET I LED = 6 V R SET where V SET =.V (typ.) and R SET is the external resistor connected from ISET pin to. LED Current Setting Table R SET LED current (ma) 0k 0..k 5. 5k 0. 0k 5. 0.k 0. DS96A-0 April 0 9

10 Typical Operation As shown in the typical application circuit, the power of the is provided from the external adapter or battery. When pin is low, the white LED for backlighting is turned off and draws a very low current from battery supply. When pin is high, provides a twice mode load switch (x) and high efficiency (x) charge pump device intended for white LED backlight applications. To maximize the power conversion efficiency, an internal sensing circuit monitors the voltage required on each constant sink input and sets the load switch and charge pump modes based on the input battery voltage and the current sink input voltage. provides the option to control the 6-steps brightness of white LEDs with a digital pulse signal applied to pin and the detailed timing of pulse dimming is shown in Figure 5. Capacitors Selection To get the better performance of, the selection 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 the output ripple, increasing the output capacitance C OUT 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 the output ripple. Input ripple is controlled by input capacitor C IN, increasing the value of input capacitance can further reduce the ripple. Practically, the input voltage ripple depends on the power supply's impedance. Tantalum capacitors are not recommended for the. If tantalum must capacitors are needed, C IN and C FLY must larger than 0μF and μf. Because tantalum capacitors' values are less than normal when using for high frequency applications. So tantalum capacitor values and ceramic capacitor values can't be the same. But C OUT can't use tantalum capacitor, because during the x mode charge pump the V OUT is negative voltage. Figure 6. Li-ion Battery Energy Capacity Versus Battery Voltage. Efficiency (%) Battery Voltage (V) Figure. Efficiency of. (I LED = 60mA, V F =.5V) PCB Board Layout All the traces of LED and running from chip to LEDs should be wide and short to reduce the parasitic connection resistance and shielded, isolated by ground plane. The Anodes of LEDs must connect to C IN, not battery directly. C FLY CP 5 0% Battery Life The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation LED Efficiency vs. V IN V IN (V) Output capacitor must be placed close to the and connect to plane. R SET 0 9 ISET C OUT 9 The exposed pad, pad should be connected to a strong ground plane for heat sinking and noise prevention. Figure. PCB Layout Guide Capacity (mah) C IN Input capacitor must be placed close to the and connect to plane. 0 DS96A-0 April 0

11 Outline Dimension D D L E E SEE DETAIL A e b A A A DETAIL A Pin # ID and Tie Bar Mark Options Note : The configuration of the Pin # identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A A A b D D E E e L W-Type 0L DFN x Package Richtek Technology Corporation Headquarter 5F, No. 0, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (6)5569 Fax: (6)5566 Richtek Technology Corporation Taipei Office (Marketing) 5F, No. 95, Minchiuan Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (6)6699 Fax: (6)66 marketing@richtek.com 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. DS96A-0 April 0