® RT9387A 700mA Charge Pump Flash LED Driver with Safety Timer General Description Features The RT9387A is a high current charge pump designed specifically for use with white LEDs in camera flash applications. Pulse Dimming Control One 700mA Flash LED Channel User Programmable Flash and Torch Current Tx Mask Function User Adjustable Safety Timer for Flash LED Protection Automatic x1/x1.5/x2 Charge Pump Mode Transition Low Input Noise and EMI Charge Pump 5.6V Over-Voltage Protection Power On/Mode Transition In-rush Protection Thermal Regulation Over-Temperature Protection Typical 0.3μ μA Low Shutdown Current Small 16-Lead WQFN Package RoHS Compliant and Halogen Free The charge pump can support one flash LED with up to 700mA of regulated constant current for uniform intensity. Highest efficiency is maintained by utilizing a x1/x1.5/x2 fractional charge pump and low dropout current regulators. The RT9387A also offers a built-in flash timeout function as a safety feature associated with the high power flash driver. The safety timer is adjustable via an external capacitor. The RT9387A provides protection features such as OverTemperature Protection (OTP) and Over-Voltage Protection (OVP). A soft-start circuitry is also included to prevent excessive inrush current at start-up and mode transitions. The RT9387A is available in the WQFN -16L 2x3 package. Applications Marking Information Camera Phone, Digital Still Cameras 07 : Product Code 07W W : Date Code Simplified Application Circuit CFLY1 C1P C1N C2P C2N VIN VBAT RFS CIN RTS Enable Flash Enable Torch Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 CFLY2 RFS RT9387A RTS ENF ENT Flash FLED VOUT CT PGND COUT CT AGND is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9387A Ordering Information Pin Configurations RT9387A (TOP VIEW) CT NC FLED Package Type QW : WQFN-16L 2x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) 16 15 14 RFS RTS ENF ENT AGND Note : Richtek products are : RoHS compliant and compatible with the current require- 12 GND 3 4 17 5 11 10 9 6 ments of IPC/JEDEC J-STD-020. 13 2 AGND VOUT C2N C1N PGND 7 8 VIN C2P C1P 1 Suitable for use in SnPb or Pb-free soldering processes. WQFN-16L 2x3 Functional Pin Description Pin No. Pin Name Pin Function 1 RFS Flash Current Setting Input. (7.86k < RFS < 367k) 2 RTS Torch Current Setting Input. (7.86k < RTS < 367k) 3 ENF Flash Mode Enable. If ENF and ENT go high together, it will enter to Tx MASK function. 4 ENT Torch Mode Enable. AGND Analog Ground. 6 VIN Power Input. (VIN must be ready before ENT and ENF) 7 C2P Fly Capacitor 2 Positive Connection. 8 C1P Fly Capacitor 1 Positive Connection. 9 PGND Power Ground. 10 C1N Fly Capacitor 1 Negative Connection. 11 C2N Fly Capacitor 2 Negative Connection. 12 VOUT Charge Pump Output. 14 FLED Flash LED Current Sink. 15 NC No Internal Connection. 16 CT Flash Timer Control Input. Connect a capacitor from CT to GND to set the flash timer. Connect to the GND pin to disable timer functionality. Connect to the VIN pin to use internal timer (1 second). 5, 13 17 GND (Exposed Pad) Ground. 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. DS9387A-02 July 2014 RT9387A C2N C2P C1P C1N Function Block Diagram x1/x1.5/x2 Charge Pump VIN OVP PGND VOUT Gate Driver Oscillator OTP Soft-Start Circuit Minimum Circuit Current Bias x1/x1.5/x2 Mode Decision FLED UVLO ENF ENT Shutdown Delay POR Bandgap Reference Current Regulation RFS MUX Current Logic Timer ENT ENF CT Low Dropout Current Source (max = 700mA/CH) Thermal Regulation VOUT AGND RTS Table 1. ENT, ENF Logic Table ENF ENT OUT 0 0 Shutdown 0 1 Torch 1 0 Flash 1 1 TX (Torch) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9387A Operation Input ULVO Tx Mask Function VIN is under voltage detection. Users can easily set Flash LED current to Torch LED current by set ENT = Hi when ENF = Hi. This function can decrease LED current and avoid interference when power amp. is active. Soft-Start The charge pump provides a soft-start function to limit the inrush current and prevent input voltage droop. The soft-start function clamps the input current over a typical period of 50μs. Pulse Dimming The RT9387A implements a pulse dimming method to control the brightness of the white LED. Users can easily configure the LED current by applying serial pulse signals to the ENT pin. There are a total of 16 steps of current level which can be set by users. Flash Safety Timer The RT9387A allows users to configure the flash timer by connecting a capacitor between CT and AGND to set the flash pulse duration. For example, a 100nF ceramic capacitor will set the flash timer to 0.294s. If CT is tied to VIN, the flash timer will be equal to the default time of 1s. To disable the flash timer, connect CT to AGND. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 Over-Temperature Protection When IC's junction temperature exceeds thermal protection temperature, charge pump will be turned off and re-turn on with a thermal hysteresis. Thermal Regulation When IC's junction temperature exceeds specific temperature (always lower than thermal protection temperature), LED current will be decreased to cool down IC's junction temperature. Output OVP When VDD − VOUT is over OVP voltage, charge pump will be off and VDD − VOUT will be clamped to OVP voltage. is a registered trademark of Richtek Technology Corporation. DS9387A-02 July 2014 RT9387A Absolute Maximum Ratings (Note 1) Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------Output Pin, VOUT ---------------------------------------------------------------------------------------------------------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 Model) ----------------------------------------------------------------------------------------------MM (Machine Model) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions −0.3V to 6V −6V to 0.3V 2.17W 46°C/W 11.5°C/W 150°C 260°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 2.8V to 5V 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 = 4.7μF, CFLY1 = CFLY2 = 1μF, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit 1.8 2 2.5 V -- 100 -- mV x1 Mode -- 1 2 x1.5 Mode -- 1.5 5 x2 Mode -- 2 5 IFLED = 250mA, ENF = 0V, ENT = VIN, RTS = 22k (Note 5) 8 0 8 % IFLED = 250mA -- 100 -- mV Start-Up Current of LEDx LED VF = 1.6V 50 60 100 A Flash Current Setting IFLED, ENF = VIN, ENT = 0V, RFS = 7.86k (Note 6), VIN > 3.6V (VF < 3.8V) -- -- 700 mA -- 1000 -- kHz Input Power Supply Under-Voltage Lockout Threshold VIN Rising Under-Voltage Lockout Hysteresis Quiescent Current IQ IFLED Accuracy Dropout Voltage VDROP Oscillator Frequency mA x1 Mode to x1.5 Mode Transition Voltage (VIN falling) VF = 3.5V, IFLED = 250mA -- 3.60 3.85 V Mode Transition Hysteresis VF = 3.5V, IFLED = 250mA -- 250 -- mV Over-Voltage Protection VIN = 4.5V 5 5.6 6 V Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9387A Parameter Symbol Test Conditions Min Typ Max Unit ENF, ENT Shutdown Current ISHDN -- 0.5 2 A ENF, ENT Low to Shutdown Delay tSHDN 3 -- -- ms -- 1 -- s IEN -- 2.5 10 A Logic-High VIH 1.5 -- -- Logic-Low VIL -- -- 0.4 Thermal Shutdown TSD -- 160 -- °C Thermal Shutdown Hysteresis TSD -- 20 -- °C Logic-High THI 2 -- -- Logic-Low TLO 3 -- 300 TOUT (By external capacitor CT = 340nF) (Note 7) Flash Time-Out EN Pull Low Current EN Input Voltage Dimming V s Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 may affect device reliability. Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of 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. Note 5. Torch Mode : RTS = 5500 IFLED Note 6. Flash Mode : RFS = 5500 IFLED Note 7. Flash Time-Out = 2.94 (s) CT F If CT pin connects to VIN, the internal timer will be enabled (1 second). If CT pin connects to GND, the external programmable timeout will be disabled. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS9387A-02 July 2014 RT9387A Typical Application Circuit CFLY1 1µF 10 8 C1P VBAT 2.8V to 5V CIN 4.7µF RFS 7.86k RTS 22k 6 VIN 1 RFS 2 CFLY2 1µF 11 7 C1N C2P C2N FLED VOUT 12 RT9387A CT 16 RTS PGND 9 5, 13 3 ENF 4 ENT Enable Flash Enable Torch Flash 14 CT COUT 4.7µF AGND Figure 1. Application Circuit of Using External Programmable Timeout CFLY1 1µF 10 8 C1P VBAT 2.8V to 5V CIN 4.7µF 6 VIN RFS 7.86k 1 RFS RTS 22k 2 CFLY2 1µF 11 7 FLED 14 VOUT 12 RT9387A RTS CT 16 PGND 9 5, 13 3 ENF 4 ENT Enable Flash Enable Torch Flash C1N C2P C2N VBAT 2.8V to 5V COUT 4.7µF AGND Figure 2. Application Circuit of Using Internal Fixed Timeout CFLY1 1µF 8 C1P VBAT 2.8V to 5V CIN 4.7µF RFS 7.86k RTS 22k Enable Flash Enable Torch 6 VIN 1 RFS 2 CFLY2 1µF 10 7 FLED RT9387A RTS 3 ENF 4 ENT 11 C1N C2P C2N Flash 14 VOUT 12 CT 16 PGND 9 AGND COUT 4.7µF 5, 13 Figure 3. Application Circuit of Disabled Timeout Function Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9387A Timing Diagram VIN 0 tOUT (by external CT) ENF 0 ENT 0 0 0 Flash IFLED 0 TxMASK 0 0 0 Flash Flash TxMASK 0 0 0 Torch tSHDN > 3ms tOUT (by external CT) 0 Flash Torch TxMASK 0 Torch 0 0 Figure 4 (a). Flash LED 3µs < TLO < 300µs VIN 0 ENF TSHDN > 3ms THI > 2µs TOUT = 1s 0 0 0 ENT 1 2 3 4 5 15 0 0 0 1 0 0 0 0 0 0 0 0 Flash Flash Flash Flash ILEDx 0 Torch TxMASK 0 TxMASK 100% Torch 0 0 15/16 14/16 11/16 13/16 12/16 100% Torch 1/16 15/16 100% 0 Torch 0 Figure 4 (b). Flash LED 16 Steps Dimming Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS9387A-02 July 2014 RT9387A Typical Operating Characteristics LED Current vs. Input Voltage Efficiency vs. Input Voltage 300 100 250 LED Current (mA) Efficiency (%) 80 60 40 20 200 150 100 50 LED VF = 3.1V, Torch Mode LED VF = 3.1V, ILED = 250mA 0 0 2.8 3.24 3.68 4.12 4.56 2.8 5 3.24 4.12 4.56 5 Input Voltage (V) x1 Mode Quiescent Current vs. Input Voltage x2 Mode Quiescent Current vs. Input Voltage 1.0 3.0 Quiescent Current (mA) Quiescent Current (mA) Input Voltage (V) 3.68 0.8 0.6 0.4 0.2 0.0 2.5 2.0 1.5 1.0 0.5 0.0 2.8 3.24 3.68 4.12 4.56 5 2.8 3.24 3.68 4.12 4.56 Input Voltage (V) Input Voltage (V) Shutdown Current vs. Input Voltage x1 Mode Inrush Current Response 5 1.0 ENT (5V/Div) VOUT (1V/Div) Shutdown Current (µA)1 0.9 0.8 0.7 0.6 C2P (2V/Div) 0.5 0.4 I IN (200mA/Div) 0.3 0.2 0.1 VIN = 3.7V, VF = 3.38V, ILED = 250mA 0.0 2.8 3.25 3.7 4.15 4.6 5.05 5.5 Time (500μs/Div) Input Voltage (V) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9387A x2 Mode Inrush Current Response x1.5 Mode Inrush Current Response ENT (5V/Div) VOUT (1V/Div) ENT (5V/Div) VOUT (2V/Div) C2P (2V/Div) C2P (5V/Div) I IN (200mA/Div) I IN (500mA/Div) VIN = 3.2V, VF = 3.38V, ILED = 250mA Time (1ms/Div) VIN = 2.8V, VF = 3.38V, ILED = 250mA Time (1ms/Div) Ripple & Spike VIN (50mV/Div) VOUT (50mV/Div) C2P (2V/Div) I IN (500mA/Div) VIN = 3.2V, VF = 3.38V, ILED = 250mA Time (1μs/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 is a registered trademark of Richtek Technology Corporation. DS9387A-02 July 2014 RT9387A Applications Information The RT9387A integrates a x1/x1.5/x2 fractional switched capacitor charge pump with current sources to power a high current LED with a programmable current for uniform intensity. It maintains high efficiency by utilizing the charge pump's automatic mode selection feature with current sources. In x1 mode, the small equivalent open loop resistance and ultra-low dropout voltage of current sources extend the x1 mode operating time and optimize the efficiency in white LED application. Soft-Start The charge pump provides a soft-start feature to limit the inrush current and prevent input voltage droop. The softstart function clamps the input current over a typical period of 50μs. Over-Temperature Protection (OTP) The RT9387A includes an Over-Temperature Protection (OTP) feature to prevent the device from being damaged due to excessive power dissipation. When IC's junction temperature exceeds thermal protection temperature, charge pump will be turned off and re-turn on with a thermal hysteresis. Input UVLO The Under-Voltage Lockout (UVLO) circuitry compares the input voltage with the UVLO threshold to ensure that the input voltage is sufficient for reliable operation. Once the input voltage exceeds the UVLO rising threshold (2V typ.), start-up begins. A 120mV (typ.) hysteresis is included to prevent supply transients from causing a shutdown. Torch Mode LED Current In Torch Mode, the current range of FLED is from 20mA to 250mA. The LED current can be set via a resistor between the RTS pin and GND. To obtain the desired LED current, follow the equation below to calculate the required resistor value : Torch Mode : RTS = 5500 IFLED Mode Select Inputs (ENF, ENT) To enter shutdown mode, pull ENF and ENT low for 3ms delay time. To enter Torch Mode, pull ENF low and pull ENT high. Please refer to section on Torch Mode LED Current for details of Torch Mode current setting. To enter Flash Mode, pull ENF high and pull ENT low. Please refer to section on Flash Mode LED current section for details of Flash Mode current setting. To enter Flash Inhibit Mode, pull ENT and ENF high. In Flash Inhibit Mode, the RT9387A limits the flash LED current to the Torch Mode current level during an RF PA pulse to reduce high loads on the battery. Table 2. ENT, ENF Logic Table ENF ENT OUT 0 0 Shutdown 0 1 Torch 1 0 Flash 1 1 TX (Torch) Brightness Control Flash Mode LED Current In Flash Mode, the current range of FLED is from 300mA to 700mA. The LED current can be set via a resistor between the RFS pin and GND. To obtain the desired LED current, follow the equation below to calculate the required resistor value : Flash Mode : RFS = 5500 IFLED Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 The RT9387A implements a pulse dimming method to control the brightness of the white LED. Users can easily configure the LED current by applying serial pulse signals to the ENT pin. There are a total of 16 steps of current level which can be set by users. A detailed operation of brightness dimming is shown below in Figure 4. is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT9387A The RT9387A allows users to configure the flash timer by connecting a capacitor between CT and AGND to set the flash pulse duration. For example, a 100nF ceramic capacitor will set the flash timer to 0.294s. If CT is tied to VIN, the flash timer will be equal to the default time of 1s. To disable the flash timer, connect CT to AGND. Calculation of the flash timeout period is shown in the following equation. 2.94 (s) x CT Flash Timeout : F Capacitor Selection Selection of appropriate peripheral capacitors is important for achieving optimized performance of the RT9387A. These capacitors affect parameters such as input/output ripple voltage, power efficiency, and the charge pumps' maximum supply current. To effectively reduce input and output ripple, low ESR ceramic capacitors are recommended. For LED driver applications, the input voltage ripple is more critical than the output ripple. In practice, the input voltage ripple depends on the power supply impedance. Increasing the value of the input capacitor, CIN, can further reduce the input ripple. The flying capacitors, CFLY1 and CFLY2, determine the supply current capability of the charge pump to influence the overall efficiency of the system. Lowering the value will improve efficiency. However, this will limit the LED current at low input voltage. For a 250mA load over the entire input range from 2.8V to 5V, it is recommended to use a 2.2μF ceramic capacitor for the flying capacitors, CFLY1 and CFLY2. where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications, 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 46°C/W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : P D(MAX) = (125°C − 25°C) / (46°C/W) = 2.17W for WQFN-16L 2x3 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 5 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. 2.4 Maximum Power Dissipation (W)1 Flash Timer Four-Layer PCB 2.0 1.6 1.2 0.8 0.4 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 5. Derating Curve of Maximum Power Dissipation Thermal Considerations For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) − TA) / θJA Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS9387A-02 July 2014 RT9387A Layout Considerations For best performance of the RT9387A, the following PCB layout guidelines should be strictly followed : Output capacitor, COUT, should be placed close to VOUT and connected to the ground plane to reduce noise coupling from the charge pumps to LED. The FLED trace running from the chip to LED should be wide and short to reduce parasitic connection resistance. The FLED trace running from the chip to LED should be wide and short to reduce the parasitic connection resistance. Input capacitor, CIN, should be placed close to VIN and connected to the ground plane. The trace of VIN in the PCB should be placed far away from sensitive devices and shielded by the ground. The traces running from the pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. CT NC FLED Output capacitor, COUT, should be placed close to VOUT and connected to the ground plane to reduce noise coupling from the charge pumps to LED. 16 15 14 RFS 1 13 AGND RTS 2 12 VOUT ENF 3 11 C2N ENT 4 10 C1N AGND 5 9 PGND GND 17 6 8 VIN C2P C1P GND Plane 7 Battery Input capacitor, CIN, should be placed close to VIN and connected to the ground plane. The trace of VIN in the PCB should be placed far away from the sensitive devices and shielded by the ground. Figure 6. PCB Layout Guide Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9387A-02 July 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT9387A 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 14 DS9387A-02 July 2014