RT9368 4-Channel Charge Pump White LED Driver with Low Dropout Current Source General Description Features The RT9368 is a high efficiency and cost effective charge pump white LED driver. It supports up to 4 white LEDs with regulated constant current for uniform intensity. The RT9368 maintains the highest efficiency by utilizing a x1/ x1.5/x2 charge pump and low dropout current regulators. z User can easily configure each LED current from 1.25mA to 20mA by a PWM dimming control. The dimming of white LEDs current can be achieved by applying a PWM signal to the EN pin. z z z z z z z z z RT9368 is available in a WQFN 3x3-16L package. z Very High Efficiency Over 80% of Battery Life Support up to 4 White LEDs Support up to 80mA Output Current 1% Typical LED Current Matching Soft Start Function Auto Charge Pump Mode Selection 250kHz Fixed Frequency Oscillator Output Over Voltage Protection PWM Dimming Control Low Input Noise and EMI RoHS Compliant and 100% Lead (Pb)-Free Ordering Information Applications RT9368 z Package Type QW : WQFN-16L 3x3 (W-Type) Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) z z Mobile Phone, DSC, MP3 White LED Backlighting LCD Display Supply Pin Configurations Note : (TOP VIEW) ments of IPC/JEDEC J-STD-020. For marking information, contact our sales representative directly or through a Richtek distributor located in your area. DS9368-07 April 2011 1 NC 2 GND 3 C1P 4 VIN LED1 12 EN 11 ISET 10 GND 17 9 5 6 7 8 VOUT Marking Information 16 15 14 13 LED4 C1N Suitable for use in SnPb or Pb-free soldering processes. VIN ` LED2 RoHS compliant and compatible with the current require- C2N ` LED3 Richtek products are : C2P WQFN-16L 3x3 www.richtek.com 1 RT9368 Typical Application Circuit + CIN 2.2uF RSET C2N C2P COUT 2.2uF VOUT VIN RT9368 EN GPIO C1N C1P CPUMP1 CPUMP2 LED4 LED3 ISET LED2 GND LED1 Figure 1. 4-WLEDs Application Circuit with PWM Dimming Function + CIN 2.2uF RSET C2N C2P COUT 2.2uF VOUT VIN RT9368 EN GPIO C1N C1P CPUMP1 CPUMP2 LED4 LED3 ISET LED2 GND LED1 Figure 2. 3-WLEDs Application Circuit with PWM Dimming Function + CIN 2.2uF RSET C2N C2P COUT 2.2uF VOUT VIN EN GPIO C1N C1P CPUMP1 CPUMP2 RT9368 LED4 LED3 ISET LED2 GND LED1 Figure 3. 2-WLEDs Application Circuit with PWM Dimming Function C PUMP1 CPUMP2 Maximum output current (total) 0.22uF 0.22uF 60mA 0.47uF 0.47uF 100mA 1uF 1uF 160mA www.richtek.com 2 DS9368-07 April 2011 RT9368 Functional Pin Description Pin No. 1 Pin Name LED 4 2, 17 (Exposed Pad) NC Pin Function Output Current for LED4. (If not in use, this pin must be connected to GND). No Internal Connection. 3, 10 GND Ground. 4 C1P Positive Terminal of Bucket Capacitor 1. 5 VIN Power Input Voltage. 6 C2N Negative Terminal of Bucket Capacitor 2. 7 C1N Negative Terminal of Bucket Capacitor 1. 8 VOUT Output Voltage Source. 9 C2P 11 ISET Positive Terminal of Bucket Capacitor 2. LED current is set by the value of the resistor R SET connected from the ISET pin to ground. Do not short the ISET pin to GND directly. 12 EN Chip Enable (Active High). Note that this pin is high impedance. 13 VIN Power Input Voltage. 14 LED 1 Output Current for LED1. (If not in use, this pin must be connected to GND). 15 LED 2 Output Current for LED2. (If not in use, this pin must be connected to GND). 16 LED 3 Output Current for LED3. (If not in use, this pin must be connected to GND). Function Block Diagram C1P C1N C2P C2N VOUT VIN OVP Soft Start Circuit + Gate Driver 250kHz OSC Mode Decision Vr2 - Min VDS UVLO LED1 LED2 LED3 LED4 16 Steps Pulse Dimming Controller EN ISET Shutdown Delay Current Source GND Current Bias DS9368-07 April 2011 www.richtek.com 3 RT9368 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 2) WQFN-16L 3x3, θJA ------------------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------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 1.47W 68°C/W 150°C 260°C −40°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 = COUT = CFLY = 1uF (ESR = 30mΩ), TA = 25°C, unless otherwise specification) Parameter Symbol Test Condition Min Typ Max Units 2.8 -- 5.0 V 1.6 2.1 2.5 V -- 100 -- mV 0.5 1 2 mA 1.5 2.5 5 mA 0 0.1 10 μA V TS_x1.5 VF = 3.5V, IOUT = 80mA, ILEDx = 20mA -- 3.7 -- V V TS_x2 -- 3.0 -- V -- 100 -- mV 1.25 -- 20 mA −8 -- +8 % −5 -- +5 % Input Input Supply Voltage V IN Under-voltage Lockout Threshold VIN Rising Under-voltage Lockout Hysteresis Quiescent of x1 Mode IQ_x1 Quiescent of x2 Mode IQ_x2 Shutdown Current ISHDN x1 mode to x1.5 mode Transition Voltage (V IN falling) x1.5 mode to x2 mode Transition Voltage (V IN falling) x1 Mode, No Load, All LED pins connected to GND, VIN = 4V x2 Mode, No Load, All LED pins floating, VIN = 3.5V VEN = 0.4V, VIN = 2.8V to 5.5V VF = 3.5V, IOUT = 80mA, ILEDx = 20mA Hysteresis of Mode Transition Output Current Range of ILEDx 2.8 < VIN < 5.5@V F = 3.2, IOUT = 60mA 3.0 < VIN < 5.5@V F = 3.4, IOUT = 80mA 3.3 < VIN < 5.5@V F = 3.8, IOUT = 80mA ILEDx Accuracy Current Matching ILED-ERR 100% Setting To be continued www.richtek.com 4 DS9368-07 April 2011 RT9368 Parameter Symbol Test Condition Min Typ Max Units Logic-High VIH 1.5 -- -- V Logic-Low VIL -- -- 0.4 V Enable EN Threshold Voltage Logic-High IIH V IH = VIN -- 1 10 μA Logic-Low IIL V IL = GND -- 1 10 μA T SHDN PWM Dimming -- 8 -- ms PWM Dimming Frequency fPWM Minimum Turn On > 30μs 250 -- 32k Hz Oscillator Frequency fOSC -- 250 -- kHz EN Current EN Low Time for Shut Down Frequency 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 highly recommended. Note 4. The device is not guaranteed to function outside its operating conditions. DS9368-07 April 2011 www.richtek.com 5 RT9368 Typical Operating Characteristics Efficiency vs. Input Voltage Input Current vs. Input Voltage 4.5 95 90 x2 Mode 3.5 85 3 80 Efficiency (%) Input Current (mA) 4 2.5 2 x1 Mode 1.5 75 x1.5 65 1 60 0.5 55 0 x1 70 x2 50 2.6 3.1 3.6 4.1 4.6 5.1 5.6 2.6 3 3.4 Input Voltage (V) 3.8 4.2 4.6 5 5.4 5.8 Input Voltage (V) LED Current vs. Input Voltage Output Voltage vs. Input Voltage 22 5.5 21 Output Voltage (V) LED Current (mA) 5 20 LED1 LED2 LED3 LED4 19 18 17 4.5 4 3.5 16 15 3 2.6 VIN ac (100mV/Div) 3 3.4 3.8 4.2 4.6 5 5.4 2.4 3.2 3.6 4 4.4 4.8 5.2 5.6 Input Voltage (V) EN Pin Shutdown Response x1.5 Mode Inrush Current Response VIN = 3.6V VIN ac (200mV/Div) VOUT (2V/Div) VOUT (2V/Div) EN (1V/Div) EN (1V/Div) IIN (200mA/Div) ILED (10mA/Div) Time (5ms/Div) www.richtek.com 6 2.8 Input Voltage (V) VIN = 3.3V Time (50us/Div) DS9368-07 April 2011 RT9368 x1.5 Mode Ripple & Spike x2 Mode Ripple & Spike VIN = 3.1V, CIN = COUT = 2.2μF VIN = 3.0V, CIN = COUT = 2.2μF VIN (200mV/Div) VIN (200mV/Div) VOUT (200mV/Div) VOUT (200mV/Div) C2N (2V/Div) C2N (2V/Div) Time (1us/Div) DS9368-07 April 2011 Time (1us/Div) www.richtek.com 7 RT9368 Applications Information The RT9368 is a high efficiency charge pump white LED driver. It provides 4 channels low dropout voltage current source to regulated 4 white LEDs current. For high efficiency, the RT9368 implements x1/x1.5/x2 mode charge pump. An external RSET is used to set the current of white LED. RT9368 has input current regulation to reduce the input ripple. Soft Start The RT9368 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 off, the RT9368 won’ t sink spike current from V IN. Mode Decision The RT9368 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 When an external PWM signal is connected to the EN pin, brightness of white LED is adjusted by the duty cycle. LED Current Setting The current of white LED connected to RT9368 can be set by RSET. Every current flows through the white LED is 250 times greater than the current of RSET. The white LED can be estimated by following equation : V ILED = ( SET ) × 250 R SET Where VSET = 1.2V, and RSET is the resistor connected from ISET to GND. If the LED is not used, the LEDs pin should be connected to GND. Figure 4 shows the connection for 3LEDs application, LED4 pin is connection to GND directly. www.richtek.com 8 LED4 LED3 LED2 LED1 Figure 4. Application for 3 LEDs Layout Consideration The RT9368 is a low dropout current source for white LED driver. Careful PCB layout is necessary. For best performance, place all peripheral components 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 RT9368. ` All the traces of LED pins 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 (Pin 5) and connected to ground plane. The trace of VIN in the PCB should be placed far away the sensitive devices or shielded by the ground. ` The GND should be connected to a strong ground plane for heat sinking and noise protection. ` The connection of RSET should be isolated from other noisy traces. The short wire is recommended to prevent EMI and noise coupling. ` Output capacitor (COUT) should be placed close to VOUT and connected to ground plane to reduce noise coupling from charge pump to LEDs. ` 6. The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. DS9368-07 April 2011 RT9368 LED3 LED2 LED1 VIN 16 15 14 13 All the traces of LED pins running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. The connection of RSET should be isolated from other noisy traces. The short wire is recommended to prevent EMI and noise coupling. GND 3 10 GND C1P 4 9 C2P C1 8 ISET VOUT 11 7 2 C1N NC 6 EN C2N 12 5 1 VIN LED4 The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. CIN RSET The GND should be connected to a strong ground plane for heat sinking and noise protection. C2 COUT Output capacitor (COUT) should be placed close to VOUT and connected to ground plane to reduce noise coupling from charge pump to LEDs. Input capacitor (CIN) should be placed Ground Plane Battery close to VIN (Pin 5) and connected to ground plane. The trace of VIN in the PCB should be placed far away the sensitive devices or shielded by the ground. Figure 5 DS9368-07 April 2011 www.richtek.com 9 RT9368 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 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 10 DS9368-07 April 2011