RT9293BGJ6

RT9293 Small Package, High Performance, Asynchronies Boost for 10 WLED Driver General Description Features The RT9293 is a high frequency, asynchronous boost converter. The internal MOSFET can support up to 10 White LEDs for backlighting and OLED power application, and the internal soft start function can reduce the inrush current. The device operates with 1-MHz fixed switching frequency to allow small external components and to simplify possible EMI problems. For the protection, the RT9293A provides 50V OVP and the RT9293B provides 50V/20V OVP to allow inexpensive and small-output capacitors with lower voltage ratings. The LED current is initially set with the external sense resistor RSET. The RT9293 is available in the tiny package type TSOT-23-6 and WDFN-8L 2x2 packages to provide the best solution for PCB space saving and total BOM cost. z z z z z z z z z z z Applications z z Ordering Information RT9293 (- ) z z Package Type J6 : TSOT-23-6 QW : WDFN-8L 2x2 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) OVP Voltage Default : 50V (RT9293A/B) 20 : 20V (RT9293B) Feedback Voltage Reference A : 104mV B : 300mV Note : VIN Operating Range : 2.5V to 5.5V Internal Power N-MOSFET Switch Wide Range for PWM Dimming (100Hz to200kHz) Minimize the External Component Counts Internal Soft Start Internal Compensation Under Voltage Protection Over Voltage Protection Over Temperature Protection Small TSOT-23-6 and 8-Lead WDFN Packages RoHS Compliant and Halogen Free Cellular Phones Digital Cameras PDAs and Smart Phones and MP3 and OLED. Portable Instruments Pin Configurations (TOP VIEW) VIN VOUT EN 6 5 4 2 3 LX GND FB TSOT-23-6 ` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. GND 1 VIN 2 VOUT 3 EN 4 GND Richtek products are : 9 8 7 6 5 LX NC FB GND WDFN-8L 2x2 Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. DS9293-01 April 2011 www.richtek.com 1 RT9293 Typical Application Circuit L 22µH to 47µH D VOUT LX VIN VOUT VIN CIN 2.2µF COUT 1µF RT9293 10 WLEDs Chip Enable EN GND FB RSET Functional Pin Description Pin No. RT9293□ GJ6 RT9293□ GQW 1 8 2 1, 5, 9 (Exposed pad) 3 Pin Name Pin Function LX Switching Pin. GND Ground Pin. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 6 FB Feedback Pin, put a resistor to GND to setting the current. 4 4 EN Chip Enable (Active High). 5 3 VOUT Output Voltage Pin. 6 2 VIN Input Supply. -- 7 NC No Internal Connection. Function Block Diagram LX VIN UVLO VOUT OCP Internal Compensation Internal Soft Start OVP OTP Logic Control, Minimum On Time PWM CurrentSense + + EA GM Driver GND + - Slope Compensation LPF Enable Logic Shutdown 20ms PWM Oscillator Reference Voltage VREF 1µA FB www.richtek.com 2 Bias Current EN DS9293-01 April 2011 RT9293 Absolute Maximum Ratings z z z z z z z z z (Note 1) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ −0.3V to 6V Switching Pin, LX ---------------------------------------------------------------------------------------------------------- −0.3V to 50V VOUT ------------------------------------------------------------------------------------------------------------------------- −0.3V to 46V Other Pins ------------------------------------------------------------------------------------------------------------------- −0.3V to 6V Power Dissipation, PD @ TA = 25°C TSOT-23-6 ------------------------------------------------------------------------------------------------------------------WDFN−8L 2x2 -------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) TSOT-23-6, θJA ------------------------------------------------------------------------------------------------------------WDFN−8L 2x2, θJA -------------------------------------------------------------------------------------------------------WDFN−8L 2x2, θJC -------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------- Recommended Operating Conditions z z 0.392W 0.606W 255°C/W 165°C/W 20°C/W 260°C 150°C −65°C to 150°C (Note 3) Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.7V, CIN = 2.2μF, COUT = 0.47μF, IOUT = 20mA, L = 22μH, TA = 25°C, unless otherwise specified) Parameter Symbol Input Voltage VIN Under Voltage Lock Out VUVLO Test Conditions UVLO Hysteresis Min Typ Max Unit 2.5 -- 5.5 V 2 2.2 2.45 V -- 0.1 -- V Quiescent Current IQ FB = 1.5V, No Switching -- 400 600 μA Supply Current IIN FB = 0V, Switching -- 1 2 mA Shutdown Current ISHDN VEN < 0.4V -- 1 4 μA Line Regulation VIN = 3 to 4.3V -- 1 -- % Load Regulation 1mA to 20mA -- 1 -- % 0.75 1 1.25 MHz Maximum Duty Cycle 90 92 -- % Clock Rate 0.1 -- 200 kHz 94 104 114 285 300 315 -- 0.7 1.2 Operation Frequency Feedback Reference Voltage On Resistance fOSC RT9293A RT9293B VREF RDS(ON) mV Ω To be continued DS9293-01 April 2011 www.richtek.com 3 RT9293 Parameter EN Threshold Voltage Symbol Test Conditions Typ Max Logic-High VIH 1.4 -- -- Logic-Low VIL -- -- 0.5 EN Sink Current IIH EN Hysteresis Over-Voltage Threshold Min OVP = 50V RT9293B-20 VOVP -- 1 -- -- 0.1 -- 42 46 50 16 17.5 20 Unit V μA V V Over-Current Threshold IOCP 1 1.2 -- A OTP TOTP -- 160 -- °C -- 30 -- °C -- 20 -- ms OTP Hysteresis Shutdown Delay TSHDN   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 low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. The case point of θJC is on the expose pad for the WDFN package. Note 3. The device is not guaranteed to function outside its operating conditions. www.richtek.com 4 DS9293-01 April 2011 RT9293 Typical Operating Characteristics Efficiency vs. Input Voltage Efficiency vs. Output Current 100 100 VIN = 4.5V 80 80 VIN = 4V Efficiency (%) 70 Efficiency (%) ILOAD = 30mA 90 90 60 50 40 30 20 ILOAD = 10mA 70 ILOAD = 20mA 60 50 40 30 20 10 10 VOUT = 10V VOUT = 34V 0 0 0 0.05 0.1 0.15 0.2 0.25 0.3 2.5 3 3.5 Output Current (A) 4.5 5 Quiescent Current vs. Input Voltage 500 35 450 Quiescent Current (µA) 40 30 25 20 15 400 350 300 250 VFB = 1.5V VIN = 3.7V, VOUT = 34V 200 10 5 15 25 35 45 55 65 75 2.5 85 3 3.5 4 4.5 5 5.5 Input Voltage (V) Output Current (mA) Frequency vs. Temperature Frequency vs. Input Voltage 1100 1100 1050 1050 Frequency (kHz) Frequency (kHz) 5.5 Input Voltage (V) Output Voltage vs. Output Current Output Voltage (V) 4 1000 950 900 1000 950 900 850 850 VIN = 3.7V, ILED = 20mA ILED = 20mA 800 800 2.5 3 3.5 4 4.5 Input Voltage (V) DS9293-01 April 2011 5 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (°C) www.richtek.com 5 RT9293 Reference Voltage vs. Input Voltage Reference Voltage vs. Temperature 0.32 0.34 Reference Voltage (V) Reference Voltage (V) 0.33 0.29 VOUT = 34V, IOUT = No Load 0.26 10WLED, ILED = 20mA 0.23 0.2 0.32 VIN = 3V 0.31 VIN = 3.7V 0.30 VIN = 4.2V 0.29 0.28 0.27 ILED = 20mA 0.17 0.26 2.5 3 3.5 4 4.5 5 5.5 -40 -15 35 60 85 Temperature (°C) Input Voltage (V) Reference Voltage vs. Output Current Enable Threshold vs. Input Voltage 1.00 0.314 0.98 VIN = 3V 0.310 Rising 0.96 0.306 VIN = 4.2V VIN = 3.7V 0.302 0.298 Enable Voltage (V) Reference Voltage (V) 10 0.94 0.92 0.90 0.88 Falling 0.86 0.84 0.294 VOUT = 34V 0.82 0.80 0.290 0 5 10 15 20 25 2.5 30 3 3.5 4 4.5 Output Current (mA) Input Voltage (V) LED Current vs. Duty Power On from EN 5 5.5 25 LED Current (mA) 20 VEN (2V/Div) 15 f f f f 10 = 200Hz = 2kHz = 20kHz = 200kHz 5 VOUT (10V/Div) 6WLED, ILED = 20mA, VIN = 3.7V VIN = 3.7V, ILED = 20mA 0 0 10 20 30 40 50 60 70 80 90 100 Time (1ms/Div) Duty (%) www.richtek.com 6 DS9293-01 April 2011 RT9293 Power Off from EN Ripple Voltage VIN (20mV/Div) VEN (2V/Div) VOUT (20mV/Div) VOUT (10V/Div) VIN = 3.7V, ILED = 20mA VIN = 3.7V, ILED = 20mA Time (1ms/Div) Time (500ns/Div) PWM Dimming from EN PWM Dimming from EN f = 20kHz f = 200Hz VEN (4V/Div) VEN (4V/Div) I LED (10mA/Div) I LED (10mA/Div) VIN = 3.7V, ILED = 20mA Time (1ms/Div) DS9293-01 April 2011 VIN = 3.7V, ILED = 20mA Time (10μs/Div) www.richtek.com 7 RT9293 Applications Information LED Current Setting The loop of Boost structure will keep the FB pin voltage equal to the reference voltage VREF. Therefore, when RSET connects FB pin and GND, the current flows from VOUT through LED and RSET to GND will be decided by the current on RSET , which is equal to following equation : V ILED = REF RSET filtered reference voltage is low and the offset can cause bigger variation of the output current. So the RT9293A is not recommend to be dimming by the EN pin. For the RT9293B, the minimum duty vs frequency is listed in following table. 300mV EN VA Dimming Control a. Using a PWM Signal to EN Pin For the brightness dimming control of the RT9293, the IC provides typically 300mV feedback voltage when the EN pin is pulled constantly high. However, EN pin allows a PWM signal to reduce this regulation voltage by changing the PWM duty cycle to achieve LED brightness dimming control. The relationship between the duty cycle and FB voltage can be calculated as following equation : VFB = Duty x 300mV Where Duty = duty cycle of the PWM signal 300mV = internal reference voltage As shown in Figure 1, the duty cycle of the PWM signal is used to cut the internal 300mV reference voltage. An internal low pass filter is used to filter the pulse signal. And then the reference voltage can be made by connecting the output of the filter to the error amplifier for the FB pin voltage regulation. However, the internal low pass filter 3db frequency is 500Hz. When the dimming frequency is lower then 500Hz, VA is also a PWM signal and the LED current is controlled directly by this signal. When the frequency is higher than 500Hz, PWM is filtered by the internal low pass filter and the VA approach a DC signal. And the LED current is a DC current which elimate the audio noise. Two figures of PWM Dimming from EN are shown in Typical Operating Characteristics section and the PWM dimming frequency is 200Hz and 20kHz respectively. But there is an offset in error amplifier which will cause the VA variation. In low PWM duty signal situation, the www.richtek.com 8 + EA - To Controller FB Figure 1. Block Diagram of Programmable FB Voltage Using PWM Signal Duty Minimum Dimming frequency < 500Hz Dimming frequency > 500Hz 4% 10% b. Using a DC Voltage Using a variable DC voltage to adjust the brightness is a popular method in some applications. The dimming control using a DC voltage circuit is shown in Figure 2. As the DC voltage increases, the current f lows through R3 increasingly and the voltage drop on R3 increase, i.e. the LED current decreases. For example, if the VDC range is from 0V to 2.8V and assume the RT9293 is selected which VREF is equal to 0.3V, the selection of resistors in Figure 2 sets the LED current from 21mA to 0mA. The LED current can be calculated by the following equation. R3 × (VDC − VREF ) VREF − R4 ILED = RSET VIN 2.5V to 5.5V L 10µH to 47µH VOUT D COUT 1µF CIN 2.2µF RT9293 VIN GND FB LX VOUT EN WLEDs Chip Enable R3 10k R4 85k RSET 16 VDC Dimming 0V to 2.8V Figure 2. Dimming Control Using a DC Voltage DS9293-01 April 2011 RT9293 c. Using a Filtered PWM signal Another common application is using a filtered PWM signal as an adjustable DC voltage for LED dimming control. A filtered PWM signal acts as the DC voltage to regulate the output current. The recommended application circuit is shown as Figure 3. In this circuit, the output ripple depends on the frequency of PWM signal. For smaller output voltage ripple (10k R2 VOUT L 10µH to 47µH D VIN 2.5V to 5.5V COUT 1µF CIN 2.2µF By the above equation and the application circuit shown in Figure 3, and assume the RT9293 is selected which VREF is equal to 0.3V. Figure 4 shows the relationship between the LED current and PWM duty cycle. For example, when the PWM duty is equal to 60%, the LED current will be equal to 8.6mA. When the PWM duty is equal to 40%, the LED current will be equal to 12.7mA. L 10µH to 47µH COUT 1µF RT9293 GND CIN 2.2µF LX VIN VOUT RT9293 LX VIN WLEDs GND Chip Enable EN FB R3 10k VOUT EN FB R4 3k R1 Chip Enable RSET 16 R2 CDC 1µF RDC 82k Figure 5. Constant Output Voltage Application 2.8V 0V PWM Signal Figure 3. Dimming Control Using a Filtered PWM Signal VIN V OUT L 22µH D 20 18 COUT 1µF CIN 2.2µF RT9293 16 LED Current (mA) VOUT D VIN 14 GND 12 10 Chip Enable 8 EN LX … VOUT FB 3 x 13 WLEDs 6 RSET 4 Figure 6. Application for Driving 3 X 13 WLEDs 2 0 0 20 40 60 80 100 PWM Duty (%) Figure 4. PWM Duty Cycle vs. LED Current DS9293-01 April 2011 www.richtek.com 9 RT9293 Application for Driving 3 x 13 WLEDs Inductor Selection The RT9293 can drive different WLEDs topology. For example, the Figure 6 shows the 3x13 WLEDs and total current is equal to 260mA. The total WLEDs current can be set by the RSET which is equal to following equation. The recommended value of inductor for 10 WLEDs applications is from 10µH to 47µH. Small size and better efficiency are the major concerns for portable devices, such as the RT9293 used for mobile phone. The inductor should have low core loss at 1MHz and low DCR for better efficiency. The inductor saturation current rating should be considered to cover the inductor peak current. ITotal = VREF RSET Power Sequence In order to assure the normal soft start function for suppressing the inrush current the input voltage should be ready before EN pulls high. Soft-Start The function of soft-start is made for suppressing the inrush current to an acceptable value at the beginning of poweron. The RT9293 provides a built-in soft-start function by clamping the output voltage of error amplifier so that the duty cycle of the PWM will be increased gradually in the soft-start period. Current Limiting The current flow through inductor as charging period is detected by a current sensing circuit. As the value comes across the current limiting threshold, the N-MOSFET will be turned off so that the inductor will be forced to leave charging stage and enter discharging stage. Therefore, the inductor current will not increase over the current limiting threshold. OVP/UVLO/OTP The Over Voltage Protection is detected by a junction breakdown detecting circuit. Once VOUT goes over the detecting voltage, LX pin stops switching and the power N-MOSFET will be turned off. Then, the VOUT will be clamped to be near VOVP. As the output voltage is higher than a specified value or input voltage is lower than a specified value, the chip will enter protection mode to prevent abnormal function. As the die temperature is higher then 160°C, the chip also will enter protection mode. The power MOSFET will be turned off during protection mode to prevent abnormal operation. Capacitor Selection Input ceramic capacitor of 2.2µF and output ceramic capacitor of 1µF are recommended for the RT9293 applications for driving 10 series WLEDs. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges. 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 the recommended operating conditions specification of RT9293, the maximum junction temperature of the die is 125°C. The junction to ambient thermal resistance θJA is layout dependent. The junction to ambient thermal resistance for TSOT-23-6 package is 255°C/W and for WDFN-8L 2x2 package is 165°C/W on the standard JEDEC 51-3 single layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula : PD(MAX) = (125°C − 25°C) / (165°C/W) = 0.606W for WDFN-8L 2x2 packages PD(MAX) = (125°C − 25°C) / (255°C/W) = 0.392W for TSOT-23-6 packages www.richtek.com 10 DS9293-01 April 2011 RT9293 The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. For RT9293 packages, the Figure 7 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed. Maximum Power Dissipation (W) 0.8 Single Layer PCB Layout Consideration For best performance of the RT9293, the following guidelines must be strictly followed. } Input and Output capacitors should be placed close to the IC and connected to ground plane to reduce noise coupling. } The GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection. } Keep the main current traces as possible as short and wide. } LX node of DC-DC converter is with high frequency voltage swing. It should be kept at a small area. } Place the feedback components as close as possible to the IC and keep away from the noisy devices. 0.7 WDFN-8L 2x2 0.6 0.5 0.4 TSOT-23-6 0.3 0.2 0.1 The inductor should be placed as close as possible to the switch pin to minimize the noise coupling into other circuits. LX node copper area should be minimized for reducing EMI. GND 0 0 25 50 75 100 125 Ambient Temperature (°C) The COUT should be connected directly from the output schottky diode to ground rather than across the WLEDs COUT Figure 7. Derating Curves for RT9293 Packages VIN CIN should be placed as closed as possible to VIN pin for good filtering. D L LX 1 6 VIN GND 2 5 VOUT 3 4 EN CIN RSET FB WLEDs FB node copper area should be minimized and keep far away from noise sources (LX pin) and RS should be as close as possible to FB pin. Figure 8. The Layout Consideration of the RT9293 Table 1. Recommended Components for Typical Application Circuit Reference Qty Part Number Description D 1 SR26 CIN 1 EMK107BJ225MA-T Capacitor, Ceramic, 2.2µF/16V X5R Taiyo Yuden COUT 1 GMK107BJ105KA Capacitor, Ceramic, 1µF/50V X5R Taiyo Yuden RSET 1 RC0603FR Resistor 15Ω, 1% YAGEO L 1 NR4018T220M Inductor, 22µH Taiyo Yuden DS9293-01 April 2011 Schottky Diode Manufacture PANJIT www.richtek.com 11 RT9293 Outline Dimension H D L C B b A A1 e Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.300 0.559 0.012 0.022 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 TSOT-23-6 Surface Mount Package www.richtek.com 12 DS9293-01 April 2011 RT9293 D2 D L E E2 1 SEE DETAIL A 2 e A A1 1 2 1 b 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. Dimensions In Millimeters Dimensions In Inches Symbol 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 0.200 0.300 0.008 0.012 D 1.950 2.050 0.077 0.081 D2 1.000 1.250 0.039 0.049 E 1.950 2.050 0.077 0.081 E2 0.400 0.650 0.016 0.026 e L 0.500 0.300 0.020 0.400 0.012 0.016 W-Type 8L DFN 2x2 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: 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. DS9293-01 April 2011 www.richtek.com 13