eup2530 ds2530 ver1.0 sep. 2012 1 bkf 10 white led boost converter with pwm dimming and single-wire series interface description the eup2530 is a constant current step-up converter specifically designed to drive white leds. with a 4 5v rated integrated switch fet, the step-up converter supports up to 10 white leds in series connection, so the led currents are identical for uniform brightne ss. the boost converter runs at 1.0mhz fixed switching frequency with 1.3a switch current limit, and allow s for the use of a high brightness led in general lig hting. the maximum white led current is set with the external sensor resistor r fb , and the feedback voltage is regulated to 200mv, as shown in the typical applica tion. during the operation, the led current can be controlled through the en pin in two modes. with a 8khz or higher frequency pwm dimming signal on en pin, eup2530 operates in pwm dimming mode, which the duty cycle determines the feedback refere nce voltage. eup2530 can operate in digital dimming mod e also, which a single wire interface on the en pin i s integrated to adjust the fb voltage in 32 steps. in either digital or pwm mode, the eup2530 does not generate audible noises on the output capacitor. for the protection, the eup2530 provides 41v ovp to prevent damage from led open. the eup2530 is available in low profile tsot23-6 package. typical application circuit features 2.6v to 5.5v input range 41v output over voltage protection internal soft-start internal compensation single-wire serial pulse interface to set led current with 32-step scale external pwm dimming with 8khz - 100khz frequency range internal 45v n-fet 1mhz fixed switching frequency over voltage protection over thermal protection v in under voltage lockout available in tsot23-6 package rohs compliant and 100% lead (pb)-free halogen-free applications mobile phones gps navigation systems portable media players handheld devices, digital camera portable game machines figure 1. white led application
eup2530 ds2530 ver1.0 sep. 2012 2 pin configurations package type pin configurations tsot23-6 pin description pin tsot23-6 description sw 1 switch pin. this is the drain of the internal power switch. connect inductor/diode here. minimize trace area at this pin to reduce emi. gnd 2 common ground. connect the pin to the ground plane. fb 3 feedback pin. reference voltage is 0.2v. connect ca thode of lowest led and resistor here. calculate resistor value according to the for mula: r fb =0.2/iled en 4 enable pin of the boost regulator. it is a multi-fu nctional pin which can be used for enable control, digital and pwm dimming control. out 5 output voltage and over voltage protection. in 6 input supply voltage.
eup2530 ds2530 ver1.0 sep. 2012 3 ordering information order number package type marking operating temperat ure range EUP2530OIR1 tsot23-6 xxxxx a200 -40 c to +85c eup2530 lead free code 1: lead free, halogen free packing r: tape & reel operating temperature range i: industry standard package type o: tsot block diagram figure 2.
eup2530 ds2530 ver1.0 sep. 2012 4 absolute maximum ratings (1) in, en, fb to gnd --------------------------------- --------------------------------- -0.3v to 6v out,sw to gnd ------------------------------------- ------------------------------- -0.3v to 45v power dissipation, p d @ t a =25c tsot23-6 ------------------------------------------ ----------------------------------- 0.5w package thermal resistance tsot23-6, ja -------------------------------------------------- ---------------------- 200c/w maximum junction temperature ---------------------- ----------------------------- 125c lead temperature (soldering, 10sec.) -------------- ------------------------------- 260c storage temperature range ------------------------- -------------------------------- -65c to +150c recommend operating conditions (2) operating temperature range --------------------------------------------------- - -40c to +85c supply voltage , v in --------------------------------------------------- -------------- 2.6v to 5.5v note (1): stress beyond those listed under absolut e maximum ratings may damage the device. note (2): the device is not guaranteed to function outside the recommended operating conditions. electrical characteristics (v in =3.6v, v out =34v, c out =1f, c in =4.7f, l1=10h, r fb =8 ,t a = -40c to+85c. unless otherwise noted. typical values are at t a = +25c) eup2530 symbol parameter conditions min. typ. max. unit uvlo under voltage lock out rising 2.0 2.2 2.4 v maximum output voltage no switching 41 v i cc1 supply current v cc =3.6v, continuous switching 0.75 1.5 ma i cc2 quiescent current v cc =3.6v, fb=1.3v, no switching 300 700 a i cc3 shutdown current v cc =3.6v, v en <0.4v 0.1 1 a oscillator fosc operation frequency 0.8 1 1.3 mhz dmax maximum duty cycle 92 % reference voltage v fb feedback voltage 190 200 210 mv mosfet rds (on) on resistance of mosfet 0.5 0.9 ilx current limit 1.0 1.3 1.6 a control and protection v en1 shutdown voltage 0.4 0.6 v v en2 enable voltage 0.8 1.4 v r en en pin pull low resistance 500 750 k ovp ovp threshold 39 41 43 v
eup2530 ds2530 ver1.0 sep. 2012 5 0 50 100 150 200 0 10 20 30 code vfb (m v) 28 33 38 43 48 2.5 3.5 4.5 5.5 vin(v) surface temp( ) 55% 60% 65% 70% 75% 80% 85% 90% 2.5 3 3.5 4 4.5 5 5.5 v i n ( v ) v i n ( v ) v i n ( v ) v i n ( v ) efficiency(%) iled=20m a led=6 iled=30m a led=6 iled=20m a led=10 iled=30m a led=10 0 5 10 15 20 0 20 40 60 80 100 pw m duty(%) iled (m a ) f=8k f=10k f=20k f=50k f=80k f=100k 0 typical operating characteristics unless others specified, vin=3.6v, l=10 h, cin=4.7 f, cout=1 f, rfb=10ohm, iled=20ma, led array:10s1p efficiency vs. vin single wire dimming thermal vs. vin@iled=20ma vin=3.6v en direct pwm dimming vs. iled vin=3.6v soft start vin=3.6v en turn off 2ms/div v en =3.6v 2v/div v out 10v/div v fb 100mv/div i in 200ma/div 2ms/div v en =3.6v 2v/div v out 10v/div v fb 100mv/div i in 200ma/div
eup2530 ds2530 ver1.0 sep. 2012 6 typical operating characteristics (continued) unless others specified, vin=3.6v, l=10 h, cin=4.7 f, cout=1 f, rfb=10ohm, iled=20ma, led array:10s1p led open protection steady operating characteristic vin line regulation 3.6v<-->5v 10ms/div v in =3.6v 2v/div v out 10v/div v fb 100mv/div i in 100ma/div 1 s/div v out 100mv/div v fb 100mv/div v in 2v/div 200ms/div v out 50mv/div v fb 100mv/div sw 20v/div v in =3.6v 100mv/div
eup2530 ds2530 ver1.0 sep. 2012 7 application information soft-start soft-start circuitry is integrated into the ic to a void a high inrush current during start-up. after the devi ce is enabled, the eup2530 attain soft-start by reduce th e internal gm to 1/20 to limit the start-up duty cycl e, which ensures that the output voltage rises slowly to reduce the input current. shutdown the eup2530 enter shutdown when en is less than 0.4 v for more than 8ms. in shutdown mode, the input supp ly current for the device is less than 1 a (max). although the internal fet does not switch in shutdown, there is still a dc current path between the input and the l eds through the inductor and schottky diode. the minimu m forward voltage of the led array must exceed the maximum input voltage to ensure that the leds remai n off in shutdown. ovp/otp/uvlo/oc the over voltage protection is detected by an inter nal resistor divider from out to gnd. once v out goes over the threshold voltage, sw pin stops switching and recover until v out voltage drops 2.0v. the over thermal protection will occurs as the junc tion temperature is higher then 150c, the chip also wil l re-enter normal operation when the junction tempera ture cools to 130c. the eup2530 is also disabled until v in exceeds the uvlo threshold of 2.2v (typ). hysteresis on uvlo is approximately 0.2v. the eup2530 also integrated a 1.3a cycle-to-cycle o ver current protection to prevent the external componen t damage. led current setting eup2530 led current can be set in two modes through en pin, pwm dimming and single wire dimming. in both dimming modes, led current is calculated using equation1. ---------------------------------(1) where: i led = output current of leds v fb = regulated voltage of fb r fb = current sense resistor in order to have an accurate led current, precision resistors are preferred (1% is recommended). led current dimming mode selection the en pin is used for the control input for both dimming modes, pwm dimming and the single wire dimming. the dimming mode for the eup2530 is selected each time when the device is enabled. the default dimming mode is pwm dimming. to enter singl e wire mode, the figure 4 digital pattern on the en p in must be recognized by the ic every time the ic star ts from the shutdown mode. 1. pull en pin high to enable the eup2530, and to s tart the single wire detection window; 2. en first high level hold on time between 1ms to 4ms(2.5ms is recommended), eup2530 will enter single wire mode. otherwise, eup2530 will operate in pwm dimming mode; 3. mode selection window re-starts only after en pi n pull low more than 8ms, and then en encounter a low to high transition; pwm dimming control when the en pin is constantly high, the fb voltage is regulated to 200mv typically. however, the en pin allows a pwm signal to reduce this regulation volta ge; therefore, it achieves led brightness dimming. the relationship between the duty cycle and fb voltage is given by equation2. ----------------------------(2) where: duty = duty cycle of the pwm signal 200mv = internal reference voltage as shown in figure 3, the ic chops up the internal 200mv reference voltage at the duty cycle of the pw m signal. the pulse signal is then filtered by an int ernal low pass filter. the output of the filter is connected to the error amplifier as the reference voltage for the fb pin regulation. therefore, although a pwm signal is use d for brightness dimming, only the wled dc current is modulated, which is often referred as analog dimmin g. this eliminates the audible noise which often occur s when the led current is pulsed in replica of the frequency and duty cycle of pwm control. for optimu m performance, use the pwm dimming frequency in the range of 8khz to 100khz. but there is an offset in error amplifier which wil l cause the v a variation. in low pwm duty signal situation, the filtered reference voltage is low and the offset ca n cause bigger variation of the output current, so pwm dimm ing duty less than 5% is not recommended. figure 3. block diagram of programmable fb voltage using pwm signal fb fb r v led i = mv 200 duty v fb =
eup2530 ds2530 ver1.0 sep. 2012 8 single wire dimming control the en pin also provides a simple digital interface to allow single wire dimming control. the digital dimm ing can save the processor power and battery life as it does not require a pwm signal all the time, and the proc essor can enter idle mode if available. the following digital pattern on the en pin is must be sent for single wire dimming operation: figure 4. single wire dimming signal on en the number of rising edges on en pin is detected internally and decoded to the current level as illu strated in table 1 below. table1. single wire v fb setting en no. v fb (mv) en no. v fb (mv) 1 6.25 17 106.25 2 12.5 18 112.5 3 18.75 19 118.75 4 25 20 125 5 31.25 21 131.25 6 37.5 22 137.5 7 43.75 23 143.75 8 50 24 150 9 56.25 25 156.25 10 62.5 26 162.5 11 68.75 27 168.75 12 75 28 175 13 81.25 29 181.25 14 87.5 30 187.5 15 93.75 31 193.75 16 100 32 200 but there is an offset voltage in error amplifier, which cause v fb variate from the idea value. so, in low lighting situation, the lowest two codes are not recommended . capacitors selection a 4.7 f to 10 f ceramic input capacitor (c in ) and a 1 f to 4.7 f ceramic output capacitor (c out ) are sufficient for most applications. during direct pwm dimming control, a larger output capacitor will significant ly reduce audio noise induced by output capacitor, and a smal ler will enlarge the audio noise, a 1 f c out is recommended. under normal condition, a 4.7 f input capacitor is sufficient. for applications with higher output pow er, a larger input capacitor of 10 f may be appropriate. x5r and x7r capacitor types are ideal due to their stab ility across temperature range. inductor selection the recommended value of inductor for 2 to 10 wleds applications are 4.7h to 47h. small size and bett er efficiency are the major concerns for portable devi ce, such as eup2530 used for mobile phone. the inductor should have low core loss at 1mhz and low dcr for better efficiency. to avoid inductor saturation cur rent rating should be considered. schottky diode selection the current rating of the schottky diode must excee d the peak current flowing through it. the schottky diode performance is rated in terms of its forward voltag e at a given current. in order to achieve the best efficie ncy, this forward voltage should be as low as possible. the response time is also critical since the driver is operating at 1mhz. board layout careful pc board layout is required due to fast swi tching. all components must be placed as close to the devic e as possible. keep the path between the inductor l1, di ode d1, and output capacitor c out extremely short for minimal noise and ringing. the feedback components such as the sense resistor r fb must be kept close to the fb pin to prevent noise injection on the fb pin tra ce. the ground return of c in and c out should be tied close to the gnd pin. see the eup2530 demo board layout for reference. figure 5. demo board
eup2530 ds2530 ver1.0 sep. 2012 9 packaging information tsot23-6 millimeters inches symbols min. normal max. min. normal max. a 0.70 - 1.00 0.028 - 0.039 a1 0.00 - 0.15 0.000 - 0.006 b 0.30 - 0.50 0.012 - 0.020 d 2.70 2.90 3.10 0.106 0.114 0.122 e1 1.45 1.60 1.75 0.057 0.063 0.069 e 0.95 ref 0.037 ref e 2.60 2.80 3.00 0.102 0.110 0.118 l 0.30 - 0.60 0.012 - 0.024
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