® RT9385B 5 Channels 125mA x1/x1.5/x2 Charge Pump White LED Driver General Description Features The RT9385B 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 RT9385B can power up to 5 white 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. An internal 5-bit DAC is used for brightness control. Users can easily configure up to 32 steps of LED current by enable pin. z 85% Average Efficiency Over Li-ion Battery Discharge z Support Up to 5 White LEDs Support Up to 25mA/Per Channel Support Up to 125mA Output Current Flexible 32 Step 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 Charge Pump 5V Over Voltage Protection Power On/Mode Transition Inrush Protection 1MHz Frequency Oscillator 0.4μ μA Low Shutdown Current RoHS Compliant and Halogen Free z z z z z z z z z z Ordering Information RT9385B Package Type QW : WQFN-16L 2x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Note : Richtek products are : ` RoHS compliant and compatible with the current z z Applications z z Camera Phone, Smart Phone White LED Backlighting Pin Configurations (TOP VIEW) require` LED2 LED1 VIN ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Marking Information 16 15 14 LED3 LED4 LED5 VOUT PGND 1 13 2 12 GND 3 4 17 5 Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385B-02 January 2014 10 9 C2N 6 For marking information, contact our sales representative directly or through a Richtek distributor located in your area. 11 AGND NC VIN EN C2P 7 8 C1P The RT9385B 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 WQFN-16L 2x3 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9385B Typical Application Circuit CFLY2 1µF CFLY1 1µF 7 8 C1P 14,11 CIN 1µF 6 9 C1N C2P C2N VIN Pulse Input 10 EN LED1 LED2 LED3 LED4 LED5 RT9385B 4 VOUT COUT 1µF AGND 13 15 16 1 2 3 PGND 5 Functional Pin Description Pin No. Pin Name Pin Function 1 LED3 Current Sink for LED3. (If not in use, this pin should be connected to VIN) 2 LED4 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 NC No Internal Connection. 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 be connected to VIN) The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 17 (Exposed Pad) GND Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS9385B-02 January 2014 RT9385B Function Block Diagram C1P C1N C2P C2N VIN VOUT Soft Start Circuit OVP UVLO Gate Driver 1MHz OSC Mode Decision LED1 LED2 LED3 LED4 LED5 Pulse Dimming Controller EN PGND AGND Shutdown Delay Current Bias Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385B-02 January 2014 Current Source is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9385B 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 = 1μF, CFLY1 = CFLY2 = 1μF, ILED1 to LED5 = 25mA, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Units 2.8 -- 4.5 V 1.8 2 2.5 V -- 100 -- mV Input Power Supply Input Supply Voltage V IN Under-Voltage Lockout Threshold V UVLO Under-Voltage Lockout Hysteresis 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 VIN Rising LED Current LED Current Accuracy Current Matching Charge Pump Oscillator Frequency fOSC Mode Decision x1 Mode to x1.5 Mode Transition Voltage (V IN Falling) IOUT = 125mA, ILEDx = 25mA -- 3.65 3.8 V Mode Transition Hystersis IOUT = 125mA, ILEDx = 25mA -- 200 -- mV 4.5 5 5.5 V Protection OVP VIN – VO UT Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS9385B-02 January 2014 RT9385B Parameter Symbol Test Conditions Min Typ Max Units 3 -- -- ms Dimming EN Low to Shutdown Delay EN Low Time for Dimming TIL 0.5 -- 500 μs EN High T ime for Dimming TIH 0.5 -- -- μs En Pull Low Current IEN -- 2 -- μA Logic-Low Voltage V IL -- -- 0.2 V Logic-High Voltage V IH 1 -- 4.5 V -- 2 EN Threshold EN Pull Low Current 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. DS9385B-02 January 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9385B 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. DS9385B-02 January 2014 RT9385B 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) Pulse Dimming Operation Ripple & Spike VIN (50mV/Div) VIN = 3.7V EN (2V/Div) VOUT (50mV/Div) C2P (5V/Div) ILED (10mA/Div) IIN (200mA/Div) Time (5ms/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385B-02 January 2014 VIN = 3.1V Time (1μs/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9385B Applications Information The RT9385B 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 RT9385B 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. Soft Start 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 droop. The soft-start clamps the input current over a typical period of 50us. Mode Decision The RT9385B 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 RT9385B 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. Capacitors Selecting To get the better performance of the RT9385B, 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. Brightness Control The RT9385B implements a pulse dimming method to control the brightness of white LEDs. 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 EN pin. There are totally 32 steps of current could be set by users. The detail operation of brightness dimming is shown in the Figure 1. 30us < tIH, INIT EN Shutdown ILEDX 0 1 0.5us < tIH 2 3 0.5us < tIL < 500us 4 5 31 30 100% 31/32 30/32 29/32 28/32 3/32 3ms < tSHDN 0 1 100% 2/32 31/32 1/32 Shutdown LED connection The RT9385B 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. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 Figure 1. 32 Step Pulse Dimming and Shutdown Delay is a registered trademark of Richtek Technology Corporation. DS9385B-02 January 2014 RT9385B Thermal Considerations Layout 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 : For best performance of the RT9385B, 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. ` 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. ` The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. 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 the RT9385B, 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 All the traces of LED pins running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. 51-7 four layers thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula : Maximum Power Dissipation (W) 1.2 Four Layers PCB 1.1 1.0 0.9 WQFN-16L 2x3 0.8 0.7 0.6 Output capacitor (COUT) should be placed close to VOUT and connected to ground plane to reduce noise coupling from charge pump to LEDs. 16 15 14 LED3 1 13 AGND LED4 2 12 NC 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 PCB should be GND 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. PGND 5 17 9 C2P C2N C1N C1P The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. For RT9385B package, the Figure 2 of derating curve allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. LED2 LED1 VIN PD(MAX) = (125°C − 25°C) / (90°C/W) = 1.111W for WQFN-16L 2x3 package Figure 3. PCB Layout Guide 0.5 0.4 0.3 0.2 0.1 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 2. Derating Curve for RT9385B Package Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9385B-02 January 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9385B 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 DS9385B-02 January 2014