RT9385BGQW

® RT9385 5 Channels 125mA x1/x1.5/x2 Charge Pump White LED Driver General Description Features The RT9385 is a 5 Channel WLED driver with auto mode selection of x1, x1.5 and x2 mode with low dropout voltage in current sources. The RT9385 can power up to 5 white z 85% Average Efficiency Over Li-ion Battery Discharge z LEDs with regulated constant current for uniform intensity. Each channel (LED1 to LED5) can support up to 25mA. The part maintains highest efficiency by utilizing x1/x1.5/ x2 fractional charge pump and low dropout current regulators. For the brightness control, user can easily use a PWM signal generated from GPIO to control the brightness of WLEDs. z Support Up to 5 White LEDs Support Up to 25mA/Per Channel PWM Brightness Control 60mV Current Source Dropout 1% LED Current Accuracy 0.7% LED Current Matching Automatic x1/x1.5/x2 Charge Pump Mode Transition Low Input Noise and EMI Over Voltage Protection Power On/Mode Transition Inrush Protection 1MHz Switching Frequency 0.4μ μA Low Shutdown Current RoHS Compliant and Halogen Free The RT9385 is available in a WQFN-16L 2x3 package. Small 1μF capacitors can be used for fly capacitors. It provides the best backlighting solution with high efficiency and smallest board space for portable application. z z z z z z z z z z Ordering Information RT9385 Package Type QW : WQFN-16L 2x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Note : Richtek products are : ` z Applications z z Camera Phone, Smart Phone White LED Backlighting Pin Configurations (TOP VIEW) RoHS compliant and compatible with the current LED2 LED1 VIN 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. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385-02 January 2014 16 15 14 LED3 LED4 LED5 VOUT PGND 1 13 2 12 GND 3 4 17 5 11 10 9 6 AGND CF VIN EN C2P 7 8 C2N C1N C1P ` WQFN-16L 2x3 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9385 Typical Application Circuit CFLY2 1µF CFLY1 1µF 7 8 C1P 14,11 CIN 1µF 6 9 C1N C2P C2N VIN PWM Input 10 EN LED1 LED2 LED3 LED4 LED5 RT9385 4 VOUT COUT 1µF 12 CF CCF 0.1µF AGND 13 15 16 1 2 3 PGND 5 Functional Pin Description Pin No. Pin Name Pin Function 1 2 LED3 LED4 Current Sink for LED3. (If not in use, this pin should be connected to VIN) Current Sink for LED4. (If not in use, this pin should be connected to VIN) 3 LED5 Current Sink for LED5. (If not in use, this pin should be connected to VIN) 4 VOUT Charge Pump Output. 5 PGND Ground. 6 C2N Fly Capacitor 2 Negative Connection. 7 C1N Fly Capacitor 1 Negative Connection. 8 C1P Fly Capacitor 1 Positive Connection. 9 C2P Fly Capacitor 2 Positive Connection. 10 EN Chip Enable (Active High). 11, 14 VIN Power Input. 12 CF PWM Filter Capacitor Connection, No Connection if this pin is not in use. 13 AGND Ground. 15 LED1 Current Sink for LED1. (If not in use, this pin should be connected to VIN) 16 LED2 Current Sink for LED2. (If not in use, this pin should connected to VIN) 17 (Exposed Pad) GND The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS9385-02 January 2014 RT9385 Function Block Diagram C1P C1N C2P C2N VIN VOUT Soft Start Circuit OVP UVLO Gate Driver 1MHz OSC Mode Decision CF EN PGND AGND Shutdown Delay Current Bias Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385-02 January 2014 LED1 LED2 LED3 LED4 LED5 PWM Dimming Controller Current Source is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9385 Absolute Maximum Ratings z z z z z z z (Note 1) Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WQFN-16L 2x3 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WQFN-16L 2x3, θJA ------------------------------------------------------------------------------------------------------WQFN-16L 2x3, θJC -----------------------------------------------------------------------------------------------------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 5V 1.111W 90°C/W 15°C/W 150°C 260°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, VF = 3.5V, CIN = COUT = 1uF, CFLY1 = CFLY2 = 1μF, ILED1 to LED5 = 25mA, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit 2.8 -- 4.5 V 1.8 2 2.5 V -- 100 -- mV Input Power Supply Input Supply Voltage Under-Voltage Lockout Threshold Under-Voltage Lockout Hysteresis VIN VUVLO VIN Rising ΔV UVLO Quiescent Current IQ x1 Mode -- 1 2 mA Shutdown Current ISHDN VIN = 4.5V -- 0.4 2 μA ILEDx ILEDx = 25mA −5 0 +5 % ILEDx = 25mA −2 0 +2 % -- 1000 -- kHz PWM Dimming Frequency 1 -- 200 kHz Internal CF Resistance -- 160 -- kΩ LED Current LED Current Accuracy Current Matching Charge Pump Oscillator Frequency fOSC Mode Decision x1 Mode to x1.5 Mode Transition Voltage (VIN Falling) IOUT = 125mA, ILEDx = 25mA. -- 3.65 3.8 V Mode Transition Hystersis IOUT = 125mA, ILEDx = 25mA. -- 200 -- mV Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS9385-02 January 2014 RT9385 Parameter Symbol Test Conditions Min Typ Max Unit 4.5 5 5.5 V 3 -- -- ms Protection OVP V IN – VOUT Enable EN Low Time for Shutdown EN Threshold Logic-Low Voltage V IL -- -- 0.2 Logic-High Voltage V IH 1 -- 4.5 -- 2 -- EN Pull Low Current V μA 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 TA = 25°C on a high effective four layers thermal conductivity test board of JEDEC 51-7 thermal measurement standard. The case point of θJC is on the exposed pad for the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385-02 January 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9385 Typical Operating Characteristics LED Current vs. Input Voltage Efficiency vs. Input Voltage 100 90 LED Current (mA) 80 Efficiency (%) 70 60 50 40 30 20 10 LED VF = 3.02V 0 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 LED1 LED2 LED3 LED4 LED5 LED VF = 3.02V 2.8 5 3 4 4.2 4.4 4.6 4.8 5 Input Voltage (V) Input Voltage (V) x2 Mode Quiescent Current vs. Input Voltage x1 Mode Quiescent Current vs. Input Voltage 1.30 4.5 1.25 Quiescent Current (mA) Quiescent Current (mA) 3.2 3.4 3.6 3.8 1.20 1.15 1.10 1.05 1.00 4.0 3.5 3.0 2.5 2.0 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 Input Voltage (V) Input Voltage (V) Shutdown Current vs. Input Voltage x1 Mode Inrush Current Response 5 1 Shutdown Current (μA) 0.9 EN (5V/Div) 0.8 0.7 VOUT (1V/Div) 0.6 0.5 C2P (2V/Div) 0.4 0.3 0.2 IIN (200mA/Div) 0.1 VIN = 3.2V 0 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 Time (100μs/Div) Input Voltage (V) Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS9385-02 January 2014 RT9385 x1.5 Mode Inrush Current Response x2 Mode Inrush Current Response EN (5V/Div) VIN = 3.15V EN (5V/Div) VIN = 3.1V VOUT (1V/Div) VOUT (1V/Div) C2P (2V/Div) C2P (2V/Div) IIN (200mA/Div) IIN (200mA/Div) Time (100μs/Div) Time (100μs/Div) PWM Dimming Operation Ripple & Spike VIN = 3.7V, CCF = 56nF, Duty = 50%, f = 10kHz EN (2V/Div) VIN (50mV/Div) VOUT (50mV/Div) C2P (5V/Div) ILED (10mA/Div) IIN (200mA/Div) Time (250μs/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385-02 January 2014 VIN = 3.1V Time (1μs/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9385 Applications Information The RT9385 uses a fractional switched capacitor charge pump to power up to five 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/x2 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. Input UVLO The input operating voltage range of the LED driver is from 2.8V to 4.5V. 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. The RT9385 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 2V typically with a hysteresis of 100mV. Capacitors Selection To get the better performance of the RT9385, the selection of peripherally appropriate capacitor and value is very important. These capacitors determine some parameters such as input/output ripple voltage, power efficiency and 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 CFLY1 and CFLY2 determine the supply current capability of the charge pump to influence the overall efficiency of the system. The lower value will improve efficiency. However, it will limit the LED's current at low input voltage. For 5x25mA load over the entire input range of 2.8V to 4.5V, it is recommended to use a 1μF ceramic capacitor on the flying capacitor CFLY1 and CFLY2. Soft Start Brightness Control The charge pump employs a soft start feature to limit the inrush current. The soft-start circuit prevents the excessive inrush current and input voltage drop. The soft-start clamps the input current in a typical period of 50μs. The RT9385 implements a PWM dimming method to control the brightness of white LEDs. When an external PWM signal is connected to the EN pin, brightness of white LED is adjusted by the duty cycle. The suggested PWM dimming frequency range is from 1kHz to 200kHz. Mode Decision The RT9385 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 RT9385 automatically switches to x1.5 or x2 mode whenever the dropout condition is detected from the current source and returns to x1 mode whenever the dropout condition releases. LED connection The RT9385 supports up to 5 white LEDs. The 5 LEDs are connected from VIN to pin1, 2, 3, 15 and 16 respectively. If the LED is not used, the LED pin should be connected to VIN directly. Thermal Considerations For continuous operation, do not exceed absolute maximum operation junction temperature. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction to ambient. The maximum power dissipation can be calculated by following formula : PD(MAX) = ( TJ(MAX) − TA ) / θJA Where T J(MAX) is the maximum operation junction temperature, TA is the ambient temperature and the θJA is the junction to ambient thermal resistance. For recommended operating conditions specification of Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS9385-02 January 2014 RT9385 PD(MAX) = (125°C − 25°C) / (90°C/W) = 1.111W for WQFN-16L 2x3 package The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. For RT9385 package, the Figure 1 of derating curve allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. Four Layers PCB 1.1 1.0 0.9 ` The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. All the traces of LED pins running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. Output capacitor (COUT) should be placed close to VOUT and connected to ground plane to reduce noise coupling from charge pump to LEDs. The trace from CF pin to external capacitance should be as short as possible. 16 15 14 LED3 1 13 AGND LED4 2 12 CF LED5 3 11 VIN VOUT 4 10 EN GND Battery Input capacitor (CIN) should be 6 7 8 placed close to VIN and connected to ground plane. The trace of VIN in the GND GND PCB should be placed far away The traces running from pins to flying capacitor from the sensitive should be short and wide to reduce parasitic devices or shielded resistance and prevent noise radiation. by the ground. WQFN-16L 2x3 0.8 Input capacitor (CIN) should be placed close to VIN and connected to ground plane. The trace of VIN in the PCB should be placed far away from the sensitive devices or shielded by the ground. PGND 5 17 9 C2P C2N C1N C1P Maximum Power Dissipation (W) 1.2 ` LED2 LED1 VIN the RT9385, The maximum junction temperature is 125°C. The junction to ambient thermal resistance θJA is layout dependent. For WQFN-16L 2x3 package, the thermal resistance θJA is 90°C/W on the standard JEDEC 51-7 four layers thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula : 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Figure 2. PCB Layout Guide 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve for RT9385 Package Layout Considerations For best performance of the RT9385, the following layout guidelines should be strictly followed : ` Output Capacitor (COUT) should be placed close to VOUT and connected to ground plane to reduce noise coupling from charge pump to LEDs. ` All the traces of LED pins running from chip to LED's should be wide and short to reduce the parasitic connection resistance. ` The trace from CF pin to external capacitance should be as short as possible. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385-02 January 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9385 Outline Dimension D D2 SEE DETAIL A e E E2 L b 1 1 2 2 A A1 A3 DETAIL A Pin #1 ID and Tie Bar Mark Options 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 0.150 0.250 0.006 0.010 D 1.900 2.100 0.075 0.083 D2 0.700 0.800 0.028 0.031 E 2.900 3.100 0.114 0.122 E2 1.700 1.800 0.067 0.071 e L 0.400 0.325 0.016 0.425 0.013 0.017 W-Type 16L QFN 2x3 Package Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. www.richtek.com 10 DS9385-02 January 2014