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RT9293 1 ds9293-01 april 2011 www.richtek.com ordering information note : richtek products are : ` rohs compliant and compatible with the current require- ments of ipc/jedec j-std-020. ` suitable for use in snpb or pb-free soldering processes. pin configurations wdfn-8l 2x2 (top view) marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. applications z cellular phones z digital cameras z pdas and smart phones and mp3 and oled. z portable instruments tsot-23-6 gnd vin lx nc fb vout 7 6 5 1 2 3 4 8 en gnd 9 gnd small package, high performance, asynchronies boost for 10 wled driver general description 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 r set . 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. features z z z z z vin operating range : 2.5v to 5.5v z z z z z internal power n-mosfet switch z z z z z wide range for pwm dimming (100hz to200khz) z z z z z minimize the external component counts z z z z z internal soft start z z z z z internal compensation z z z z z under voltage protection z z z z z over voltage protection z z z z z over temperature protection z z z z z small tsot-23-6 and 8-lead wdfn packages z z z z z rohs compliant and halogen free lx gnd fb vin vout en 4 23 5 6 package type j6 : tsot-23-6 qw : wdfn-8l 2x2 (w-type) lead plating system g : green (halogen free and pb free) feedback voltage reference a : 104mv b : 300mv RT9293 ovp voltage default : 50v (RT9293a/b) 20 : 20v (RT9293b) ( ) -
RT9293 2 ds9293-01 april 2011 www.richtek.com function block diagram functional pin description pin no. RT9293 gj6 RT9293 gqw pin name pin function 1 8 lx switching pin. 2 1, 5, 9 (exposed pad) gnd ground pin. the exposed pad must be soldered to a large pcb and connected to gnd for maximum power dissipation. 3 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. typical application circuit vin en fb vout gnd RT9293 c in 2.2f r set chip enable l 22h to 47h 10 wleds lx v in c out 1f v out d logic control, minimum on time current- sense ocp driver - + + slope compensation + - pwm ea gm lpf 20ms shutdown enable logic ovp otp uvlo v ref 1a lx gnd fb vout vin en internal compensation internal soft start pwm oscillator reference voltage bias current
RT9293 3 ds9293-01 april 2011 www.richtek.com electrical characteristics parameter symbol test conditions min typ max unit input voltage v in 2.5 -- 5.5 v under voltage lock out v uvlo 2 2.2 2.45 v uvlo hysteresis -- 0.1 -- v quiescent current i q fb = 1.5v, no switching -- 400 600 a supply current i in fb = 0v, switching -- 1 2 ma shutdown current i shdn v en < 0.4v -- 1 4 a line regulation v in = 3 to 4.3v -- 1 -- % load regulation 1ma to 20ma -- 1 -- % operation frequency f osc 0.75 1 1.25 mhz maximum duty cycle 90 92 -- % clock rate 0.1 -- 200 khz RT9293a 94 104 114 feedback reference voltage RT9293b v ref 285 300 315 mv on resistance r ds(on) -- 0.7 1.2 to be continued recommended operating conditions (note 3) z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c absolute maximum ratings (note 1) z supply input voltage, v in ------------------------------------------------------------------------------------------------ ? 0.3v to 6v z switching pin, lx ---------------------------------------------------------------------------------------------------------- ? 0.3v to 50v z vout ------------------------------------------------------------------------------------------------------------------------- ? 0.3v to 46v z other pins ------------------------------------------------------------------------------------------------------------------- ? 0.3v to 6v z power dissipation, p d @ t a = 25 c tsot-23-6 ------------------------------------------------------------------------------------------------------------------- 0.392w wdfn ? 8l 2x2 -------------------------------------------------------------------------------------------------------------- 0.606w z package thermal resistance (note 2) tsot-23-6, ja ------------------------------------------------------------------------------------------------------------- 255 c/w wdfn ? 8l 2x2, ja -------------------------------------------------------------------------------------------------------- 165 c/w wdfn ? 8l 2x2, jc -------------------------------------------------------------------------------------------------------- 20 c/w z lead temperature (soldering, 10 sec.) ------------------------------------------------------------------------------- 260 c z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z storage temperature range -------------------------------------------------------------------------------------------- ? 65 c to 150 c (v in = 3.7v, c in = 2.2 f, c out = 0.47 f, i out = 20ma, l = 22 h, t a = 25 c, unless otherwise specified)
RT9293 4 ds9293-01 april 2011 www.richtek.com 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. ja is measured in the natural convection at t a = 25 c on a low effective single layer thermal conductivity test board of jedec 51-3 thermal measurement standard. the case point of jc is on the expose pad for the wdfn package. note 3. the device is not guaranteed to function outside its operating conditions. parameter symbol test conditions min typ max unit logic-high v ih 1.4 -- -- en threshold voltage logic-low v il -- -- 0.5 v en sink current i ih -- 1 -- a en hysteresis -- 0.1 -- v ovp = 50v 42 46 50 over-voltage threshold RT9293b-20 v ovp 16 17.5 20 v over-current threshold i ocp 1 1.2 -- a otp t otp -- 160 -- c otp hysteresis -- 30 -- c shutdown delay t shdn -- 20 -- ms ?
RT9293 5 ds9293-01 april 2011 www.richtek.com typical operating characteristics frequency vs. input voltage 800 850 900 950 1000 1050 1100 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) frequency (khz) i led = 20ma output voltage vs. output current 10 15 20 25 30 35 40 5 1525354555657585 output current (ma) output voltage (v) v in = 3.7v, v out = 34v efficiency vs. input voltage 0 10 20 30 40 50 60 70 80 90 100 2.533.544.555.5 input voltage (v) efficiency (%) v out = 34v i load = 10ma i load = 20ma i load = 30ma efficiency vs. output current 0 10 20 30 40 50 60 70 80 90 100 0 0.05 0.1 0.15 0.2 0.25 0.3 output current (a) efficiency (%) v out = 10v v in = 4v v in = 4.5v quiescent current vs. input voltage 200 250 300 350 400 450 500 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) quiescent current (a ) v fb = 1.5v frequency vs. temperature 800 850 900 950 1000 1050 1100 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) frequency (khz ) v in = 3.7v, i led = 20ma
RT9293 6 ds9293-01 april 2011 www.richtek.com enable threshold vs. input voltage 0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98 1.00 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) enable voltage (v) reference voltage vs. input voltage 0.17 0.2 0.23 0.26 0.29 0.32 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) reference voltage (v) v out = 34v, i out = no load 10wled, i led = 20ma rising falling reference voltage vs. output current 0.290 0.294 0.298 0.302 0.306 0.310 0.314 0 5 10 15 20 25 30 output current (ma) reference voltage (v) v out = 34v v in = 3v v in = 3.7v v in = 4.2v led current vs. duty 0 5 10 15 20 25 0 102030405060708090100 duty (%) led current (ma) f = 200hz f = 2khz f = 20khz f = 200khz 6wled, i led = 20ma, v in = 3.7v power on from en time (1ms/div) v out (10v/div) v en (2v/div) v in = 3.7v, i led = 20ma reference voltage vs. temperature 0.26 0.27 0.28 0.29 0.30 0.31 0.32 0.33 0.34 -40 -15 10 35 60 85 temperature (c) reference voltage (v) i led = 20ma v in = 3v v in = 3.7v v in = 4.2v
RT9293 7 ds9293-01 april 2011 www.richtek.com ripple voltage v in (20mv/div) time (500ns/div) v out (20mv/div) v in = 3.7v, i led = 20ma power off from en time (1ms/div) v out (10v/div) v en (2v/div) v in = 3.7v, i led = 20ma pwm dimming from en time (10 s/div) i led (10ma/div) v en (4v/div) v in = 3.7v, i led = 20ma f = 20khz pwm dimming from en time (1ms/div) i led (10ma/div) v en (4v/div) v in = 3.7v, i led = 20ma f = 200hz
RT9293 8 ds9293-01 april 2011 www.richtek.com applications information led current setting the loop of boost structure will keep the fb pin voltage equal to the reference voltage v ref . therefore, when r set connects fb pin and gnd, the current flows from v out through led and r set to gnd will be decided by the current on r set , which is equal to following equation : ref led set v i = r 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 flows 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 v ref 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. dcref ref led set r3(vv) v r4 i = r - - figure 2. dimming control using a dc voltage figure 1. block diagram of programmable fb voltage using pwm signal 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 : v fb = 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, v a 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 v a 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 v a variation. in low pwm duty signal situation, the 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. duty minimum dimming frequency < 500hz 4% dimming frequency > 500hz 10% + - ea fb to controller 300mv en v a lx fb vin en vout RT9293 gnd c in 2.2 f l c out v in 10 h to 47 h 2.5v to 5.5v 1 f v out r set wleds d chip enable r3 10k r4 85k 16 v dc dimming 0v to 2.8v
RT9293 9 ds9293-01 april 2011 www.richtek.com 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 (<100mv), the recommended frequency of 2.8v pwm signal should be above 2khz. to fix the frequency of pwm signal and change the duty cycle of pwm signal can get different output current. the led current can be calculated by the following equation : pwmref ref dc led set r3(vdutyv) v r4r i = r - - + figure 3. dimming control using a filtered pwm signal by the above equation and the application circuit shown in figure 3, and assume the RT9293 is selected which v ref 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. constant output voltage control the output voltage of the r9293 can be adjusted by the divider circuit on the fb pin. figure 5 shows the application circuit for the constant output voltage. the output voltage can be calculated by the following equations : outref r1r2 v = v ; r2 >10k r2 + 0 2 4 6 8 10 12 14 16 18 20 0 20 40 60 80 100 pwm duty (%) led current (ma) figure 4. pwm duty cycle vs. led current figure 5. constant output voltage application figure 6. application for driving 3 x 13 wleds lx fb vin en vout RT9293 gnd c in 2.2 f l c out v in 10 h to 47 h 2.5v to 5.5v 1 f v out r1 d chip enable r2 lx en vin fb vout RT9293 gnd l 22 h d c in 2.2 f v in chip enable c out 1 f v out r set 3 x 13 wleds lx fb vin en vout RT9293 gnd c in 2.2 f l c out v in 10 h to 47 h 2.5v to 5.5v 1 f v out r set wleds d chip enable r3 10k r4 3k r dc 82k 16 c dc 1 f pwm signal 0v 2.8v
RT9293 10 ds9293-01 april 2011 www.richtek.com 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 power- on. 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 v out goes over the detecting voltage, lx pin stops switching and the power n-mosfet will be turned off. then, the v out will be clamped to be near v ovp . 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. application for driving 3 x 13 wleds 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 r set which is equal to following equation. ref total set v i = r inductor selection the recommended value of inductor for 10 wleds applications is from 10 m h to 47 m h. 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. capacitor selection input ceramic capacitor of 2.2 m f and output ceramic capacitor of 1 m f 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 : p d(max) = ( t j(max) - t a ) / q ja where t j(max) is the maximum operation junction temperature, t a is the ambient temperature and the q ja 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 q ja 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 t a = 25 c can be calculated by following formula : p d(max) = (125 c - 25 c) / (165 c/w) = 0.606w for wdfn-8l 2x2 packages p d(max) = (125 c - 25 c) / (255 c/w) = 0.392w for tsot-23-6 packages
RT9293 11 ds9293-01 april 2011 www.richtek.com the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance q ja . 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. figure 7. derating curves for RT9293 packages 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 25 50 75 100 125 ambient temperature ( c) maximum power dissipation (w) wdfn-8l 2x2 ( c) tsot-23-6 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. r set v in gnd wleds 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. 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. c in should be placed as closed as possible to vin pin for good filtering. the c out should be connected directly from the output schottky diode to ground rather than across the wleds 4 2 3 5 6 1 vin vout en lx gnd fb l d c in c out figure 8. the layout consideration of the RT9293 reference qty part number description manufacture d 1 sr26 schottky diode panjit c in 1 emk107bj225ma-t capacitor, ceramic, 2.2 m f/16v x5r taiyo yuden c out 1 gmk107bj105ka capacitor, ceramic, 1 m f/50v x5r taiyo yuden r set 1 rc0603fr resistor 15 w , 1% yageo l 1 nr4018t220m inductor, 22 m h taiyo yuden table 1. recommended components for typical application circuit
RT9293 12 ds9293-01 april 2011 www.richtek.com outline dimension tsot-23-6 surface mount package 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 a a1 e b b d c h l
RT9293 13 ds9293-01 april 2011 www.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. richtek technology corporation headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 richtek technology corporation taipei office (marketing) 5f, no. 95, minchiuan road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)86672399 fax: (8862)86672377 email: marketing@richtek.com w-type 8l dfn 2x2 package 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 0.500 0.020 l 0.300 0.400 0.012 0.016 1 1 2 2 note : the configuration of the pin #1 identifier is optional, but must be located within the zone indicated. detail a pin #1 id and tie bar mark options d 1 e a3 a a1 d2 e2 l b e see detail a

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