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| mp24183 1a, 55v, programmable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 1 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the mp24183 is a 55v, 1a, white led driver suitable for either step-down or inverting step-up/down applications. it achieves 1a peak output current over a wide input supply range with excellent load and line regulation. current mode operation provides fast transient response and eases loop stabilization. fault condition protection includes thermal shutdown, cycle-by-cycle peak current limiting, input over voltage protection, open strings protection and output short circuit protection. the mp24183 incorporates both dc and pwm dimming onto a single control pin. the separate input reference ground pin allows for direct enable and/or dimming control for a positive to negative power conversion. the mp24183 requires a minimum number of readily available standard external components and is available in a 10-pin 3mm x 3mm qfn package. features ? 1a maximum output current ? unique step-up/down operation (buck- boost mode) ? wide 4.5v to 55v operating input range for step-down applications (buck mode) ? 0.28 ? internal power mosfet switch ? adjustable switching frequency ? analog and pwm dimming ? 0.198v reference voltage ? 5 a shutdown mode ? no minimum led required ? stable with low esr output ceramic capacitors ? cycle-by-cycle over current protection ? thermal shutdown protection ? open strings protection ? input over voltage protection ? output short circuit protection ? available in 10-pin 3x3 qfn package applications ? general led illuminations ? lcd backlight panels ? handheld computers ? automotive internal lighting ? portable multimedia players ? portable gps devices ?mps? and ?the future of analog ic technology? are trademarks of monolithic power systems, inc. typical application vdd ovp bst sw fb rset comp mp24183 vss ingnd en/dim off on l1 4.7 c3 100nf d1 b360a c2 2.2 c1 10 vin 4.5v mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 3 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristices v in = 12v, t a = +25 ? c, all voltages with respect to v ss , unless otherwise noted. parameters symbol condition min typ max units feedback voltage v fb 4.5v ? ? ? switch leakage v en = 0v, v sw = 0v 1 a current limit ( 5 ) 2.0 a oscillator frequency f sw v fb = 0.19v, rset=100k ? 0.5 mhz default oscillator frequency f sw_default v fb = 0.19v, rset open 1.05 1.35 1.65 mhz fold-back frequency v fb = 0v, v ovp =0v 250 khz maximum duty cycle v fb = 0.19v 90 % minimum on-time ( 5 ) t on 100 ns under voltage lockout threshold rising 3 3.3 3.6 v under voltage lockout threshold hysteresis 100 mv en input current v en = 2v 2.1 a en off threshold (w/respect to ingnd) v en falling 0.4 v en on threshold (w/respect to ingnd) v en rising 0.6 v minimum en dimming threshold v fb = 0v 0.6 0.7 0.8 v maximum en dimming threshold v fb = 0.2v 1.25 1.4 1.5 v supply current (quiescent) i q v en = 2v, v fb = 1v 0.8 1.0 ma supply current (quiescent) at en off i off v en =0v 3.4 15 a thermal shutdown ( 5 ) 150 c open led ov threshold v ovp th 1.1 1.2 1.3 v open led ov hysteresis v ovp h y s 60 mv notes: 5) guaranteed by design. mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 4 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pin functions pin # name description 1 vdd supply voltage. the mp24183 operates from a +4.5v to +55v unregulated input (with respect to vss). c1 is needed to prevent large voltage spikes from appearing at the input. 2 vss power return pin. connect to the lowest potentia l in the circuit, which is typically the anode of the schottky rectifier. this pin is the voltage reference for the regulated output voltage. for this reason care must be taken in its layout. this node should be placed outside of the d1 to c1 ground path to prevent switching current spikes from inducing voltage noise into the part. the exposed pad is also connected to this pin. 3 ovp over voltage protection pin. use a voltage divider to program ovp threshold. when the ovp pin voltage reaches the shutdown threshold 1.2v, the switch will be turned off and will recover when ovp voltage decreases sufficiently. when the ovp pin voltage (with respect to vss) is lower than 0.4v and fb pin voltage is lower than 0.1v, the chip reecognizes this as short circuit condition and the operating frequency will be folded back. program the ovp pin voltage from 0.4v to 1.2v for normal operation. 4 fb led current feedback input. mp24183 regulates the voltage across the current sensing resistor between fb and vss. conne ct the current sensing resistor from the bottom of the led strings to vss. the fb pin is connect ed to the bottom of the led strings. the regulation voltage is 0.198v. 5 comp output of error amplifier. connect a 1nf or larger capacitor on comp to improve the stability and to provide a soft on at start up and pwm dimming. 6 rset frequency set pin. connect a resistor to vss to set the switching frequency and an 1nf capacitor to vss to bypass the noise. leavi ng this pin open gets a default operating frequency 1.35mhz. 7 en/dim on/off control input and dimming command input. a voltage greater than 0.6v will turn on the chip. both dc and pwm dimming are implemented on this pin. when the en/dim pin voltage (with respect to ingnd) rises from 0. 7v to 1.4v, the led current will change from 0% to 100% of the maximum led current. to use pwm dimming, apply a 100hz to 2khz square wave signal with amplitude greater than 1.4v to this pin. 8 ingnd input ground reference. this pin is the reference for the en/dim signal. 9 bst bootstrap. a capacitor is connected between sw and bst pin to form a floating supply across the power switch driver. a 100nf or larger ceramic capacitor is recommended to provide sufficient energy to drive the powe r switch?s gate above the supply voltage. 10 sw switch output. sw is the source of the inte rnal mosfet switch. connect this pin to the power inductor and the cathode of the schottky rectifier. exposed pad should be connect ed to vss in step up/down mode. mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 5 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics vin=20v, iled=0.7a, two 3w led in series, step down application, unless otherwise noted. wled current vs dimming duty 0 100 200 300 400 500 600 700 800 0 0.2 0.4 0.6 0.8 1 1.2 dimming duty wled current(ma) wled current vs ven -100 0 100 200 300 400 500 600 700 800 0 400 800 1200 1600 ven(mv) wled current(ma) efficiency 0 10 20 30 40 50 60 70 80 90 100 0102030405060 input voltage(v) efficiency(%) 3wled, 710ma 1wled, 710ma 2wled, 710ma mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 6 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics (continued) vin=20v, iled=0.7a, two 3w led in series, step down application, unless otherwise noted. v in 10v/div. v out 5v/div. sw 10v/div. sw 10v/div. pwm 5v/div. i inductor 500ma/div. i inductor 500ma/div. i inductor 500ma/div. i inductor 500ma/div. i inductor 1a/div. i wled 500ma/div. i wled 500a/div. sw 10v/div. en 5v/div. i wled 500ma/div. sw 10v/div. en 5v/div. i wled 500ma/div. v led+ 5v/div. v dd 20v/div. sw 50v/div. sw 10v/div. ovp 1v/div. i inductor 500ma/div. 400ns/div. 2ms/div. 40us/div. 4us/div. 20ms/div. 2us/div. steady state pwm dimming en on en off open led protection vdd-vss ovp protection mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 7 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. functional block diagram figure 1?functional block diagram mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 8 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation the mp24183 is a current mode regulator. the ea output voltage is proportional to the peak inductor current. at the beginning of a cycle, m1 is off. the ea output voltage is higher than the current sense amplifier output, and the current comparator?s output is low. the rising edge of the 1.35mhz clk signal sets the rs flip-flop. its output turns on m1 thus connecting the sw pin and inductor to the input supply. the increasing inductor current is sensed and amplified by the current sense amplifier. ramp compensation is summed to the current sense amplifier output and compared to the error amplifier output by the pwm comparator. when the sum of the current sense amplifier output and the slope compensation signal exceeds the ea output voltage, the rs flip- flop is reset and m1 is turned off. the external schottky rectifier diode (d1) conducts the inductor current. if the sum of the current sense amplifier output and the slope compensation signal does not exceed the ea output for a whole cycle, then the falling edge of the clk resets the flip-flop. the output of the error amplifier integrates the voltage difference between the feedback and the 0.198v reference. the polarity is a fb pin voltage lower than 0.198v increases the ea output voltage. since the ea output voltage is proportional to the peak inductor current, an increase in its voltage also increases the current delivered to the output. open led protection if the led is open, there is no voltage on the fb pin. the duty cycle will increase until v(vdd)-v(vss) reaches 55v or ovp-vss reaches the shutdown threshold set by the external resistor divider. the top switch will turn off till the voltage v(vdd)-v(vss) and ovp- vss decreases sufficiently. dimming control the mp24183 allows both dc and pwm dimming. when the voltage on en is less than 0.6v, the chip is turned off. for analog dimming, when the voltage on en is from 0.7v to 1.4v, the led current will change from 0% to 100% of the maximum led current. if the voltage on en pin is higher than 1.4v, maximum led current will be generated. for pwm dimming, its amplitude (vdim ? vingnd) must exceed 1.4v. the pwm frequency is recommended in range of 100hz to 2khz to get a good dimming linearity. output short circuit protection the mp24183 integrates output short circuit protection. when the output is shorted to vss, the voltage on ovp pin which detects the output voltage gets smaller than 0.4v, and fb pin senses no voltage (<0.1v) as no current goes through the wled. at this condition, the operating frequency is folded back to decrease the power consumption. in buck-boost application, when there is possibility that the led+ short circuit to vss, it is recommended to add a diode from vss to ingnd to protect the ic, as shown in below figure 2 . figure 2?buck-boost application when led+ possibly short to vss mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 9 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. application information setting the led current the external resistor is used to set the maximum led current (see the schematic on front page) through the use of the equation: s e n s e l e d 0 . 1 9 8 v r i ? setting the operating frequency the resistor on rset pin is used to set the operating frequency. a 1nf capacitor is recommended to bypass this pin to gnd. the relationship between the operating frequency and the rest resistor is as the following curve. a 20k ? to 200k ? rset resistor is recommended, which sets the operating frequency from around 1.3mhz to 250khz. leaving the rset pin open will set the operating frequency to the default operating frequency 1.35mhz. frequency vs. rset 0 200 400 600 800 1000 1200 1400 0 50 100 150 200 250 frequency (khz) series1 selecting the inductor (step-down applications, see figure 3) a 1 h to 47 h inductor with a dc current rating of at least 25% percent higher than the maximum load current is recommended for most applications. for high efficiency, the inductor?s dc resistance should be less than 200m ? . refer to table 2 for suggested surface mount inductors. for most designs, the required inductance value can be derived from the following equation. sw l in out in out f i v ) v v ( v l ? ? ? ? ? ? where i l is the inductor ripple current. choose the inductor ripple current to be 30% of the maximum load current. the maximum inductor peak current is calculated from: 2 i i i l load ) max ( l ? ? ? under light load conditions below 100ma, a larger inductance is recommended for improved efficiency. also note that the maximum recommended load current is 2a if the duty cycle exceeds 35%. selecting the input capacitor the input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. the input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from passing through the input. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 4.7 f capacitor is sufficient. selecting the output capacitor the output capacitor keeps the output voltage ripple small and ensures feedback loop stable. the output capacitor impedance should be low at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended for their low esr characteristics. for most applications, a 2.2 f ceramic capacitor will be sufficient. pc board layout the high current paths (vss, vdd and sw) should be placed very close to the device with short, direct and wide traces. the input capacitor needs to be as close as possible to the vdd and vss pins. the external feedback resistors should be placed next to the fb pin. keep the switch node traces short and away from the feedback network. mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 10 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. table 2?suggested surface mount inductors manufacturer part number inductance( h) max dcr( ? ) current rating (a) dimensions l x w x h (mm 3 ) toko a921cy-4r7m 4.7 0.027 1.66 6 x 6.3 x 3 sumida cdrh4d28c/ld 4.7 0.036 1.5 5.1 x 5.1 x 3 wurth electronics 7440530047 4.7 0.038 2.0 5.8 x 5.8 x 2.8 typical application circuits figure 3?step-down white led driver application figure 4? step-up/down white led driver application mp24183 ? 1a, 55v, programable frequency white led driver mp24183 rev. 1.0 www.monolithicpower.com 11 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. figure 5? step-up white led driver application mp24183 ? 1a, 55v, programable frequency white led driver notice: the information in this document is subject to change wi thout notice. users should warra nt and guarantee that third party intellectual property rights are not infringed upon w hen integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp24183 rev. 1.0 www.monolithicpower.com 12 8/28/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information 3mm x 3mm qfn10 side view top view 1 10 6 5 bottom view 2.90 3.10 1.45 1.75 2.90 3.10 2.25 2.55 0.50 bsc 0.18 0.30 0.80 1.00 0.00 0.05 0.20 ref pin 1 id marking 1.70 0.50 0.25 recommended land pattern 2.90 note: 1) all dimensions are in millimeters. 2) exposed paddle size does not include mold flash. 3) lead coplanarity shall be 0.10 millimeter max. 4) drawing conforms to jedec mo-229, variation veed-5. 5) drawing is not to scale. pin 1 id see detail a 2.50 0.70 pin 1 id option b r0.20 typ. pin 1 id option a r0.20 typ. detail a 0.30 0.50 pin 1 id index area |
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