x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m july 2011 rev. 1.0.0 exar corporation www.exar.com 48720 kato road, fremont ca 94538, usa tel. +1 510 668-7000 ? fax. +1 510 668-7001 general description the xrp7618 is an 8-channel, high voltage, constant-current sink led driver capable of driving up to 100ma current per channel. with outputs rated at 30v, the xrp7618 can control strings of multiple leds with better than 1.5% channel to channel current matching. led channel current is programmed via an external resistor within a 10ma to 100ma range. dimming control is supported through a standard pwm scheme up to 25khz or through an analog signal. featuring exar?s smart talk tm technology, when combined with a boost converter, the xrp7618 maximizes th e overall system efficiency by dynamically reporting the minimum led voltage necessary to maintain current regulation mode. multiple channels can be combined to increase current driving capability per channel and multiple xrp7618s can be placed in parallel to drive over 8 strings of leds. an under voltage lock out, open led and over temperature protections insure safe operations under abnormal operating conditions. the xrp7618 is available in rohs compliant, ?green?/halogen free space saving 20-pin tssop (ep) package. applications ? lcd backlighting ? desktop, notebook and tv displays ? industrial and medical displays ? signage backlighting features ? 8 constant-current channels ? adjustable up to 100ma per channel ? channel paralleling for higher current ? 1.5% current matching accuracy ? up to 30v led channel voltage range ? 5v biasing voltage and control ? smart talk tm power optimization ? parallel operations support ? pwm and analog dimming ? uvlo, open led & over temperature protection ? rohs compliant halogen free, 20-pin tssop (ep) package typical application diagram fig. 1: xrp7618 typical application diagram
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 2/10 rev. 1.0.0 absolute maximum ratings these are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. v cc , iset, en, fb, sdb, pwm ...................... -0.3v to 6.0v chx .......................................................... -0.3v to 30v junction temp erature .......................................... 150c storage temperatur e .............................. - 65c to 150c power dissipat ion ................................ internal ly limited lead temperature (sol dering, 10 se c) ................... 260c esd rating (hbm - huma n body mode l) .................... 6kv esd rating (mm - machine model) ........................... 200v operating ratings input voltage range v cc .............................. 4.2v to 5.5v pwm dimming frequency .......................0.1khz to 25khz current per channel ..................................................... v chx 0.5v ........................................... 10ma to 25ma v chx 1v .............................................. 10ma to 65ma v chx 1.5v ......................................... 10ma to 110ma operating temperature range ................... -40c to 85c thermal resistance ja (tssop-20) ..................... 35c/w electrical specifications specifications with standard type are fo r an operating junction temperature of t j = 25c only. minimum and maximum limits are guaranteed through test, design, or statistical co rrelation. typical values represent the most likely parametric norm at t j = 25c, and are provided for reference purp oses only. unless otherwise indicated, v cc = 5v, r iset = 8.2k ? , t a = 25c. parameter min. typ. max. units conditions operating input voltage range v cc 4.2 5.0 5.5 v shutdown supply current 0.1 1 a v en =0v quiescent supply current 0.5 1 ma no load under voltage lockout threshold 3.6 3.8 4.0 v falling edge under voltage lockout hysteresis 200 mv iset reference voltage 1.170 1.194 1.218 v current multiplication ratio 370 400 430 i chx /i set maximum output current per channel 23 45 ma v chx =0.5v 65 70 v chx =1.0v 110 120 v chx =1.5v led current matching -1.5 1.5 % any 2 channels v chx =1.0v, i chx =60ma current sink saturation voltage 0.45 v i chx =20ma 0.8 i chx =60ma 1.2 i chx =100ma output current line regulation 2 %/v v cc =4.2v to 5.5v output current load regulation 4 % v chx =0.5v to 2.8v enable logic low 0.8 v xrp7618 is disabled enable logic high 1.8 v xrp7618 is active pwm pin logic low 0.8 v xrp7618 is disabled pwm pin logic high 1.8 v xrp7618 is active sdb pin logic low 0.4 v sdb pin logic high 2.4 v feedback output current 5 15 a thermal shutdown die temperature 160 c thermal shutdown hysteresis 20 c
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 3/10 rev. 1.0.0 block diagram fig. 2: xrp7618 block diagram pin assignment fig. 3: xrp7618 pin assignment
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 4/10 rev. 1.0.0 pin description name pin number description chx 1, 2, 3, 4, 7, 8, 9, 10 ch1 to ch8 pins connect an led between each pin and led supply rail voltage (v led ). current value is controlled by r set . connect unused channel(s) to gnd. nc 12 not connected pwm 11 pwm pin this must be held high to enable the outp ut drivers. it can be used for pwm dimming up to 25khz. if not used, connect to v cc . fbx 13 fbx input pin used in parallel configuration as an interface terminal by connecting it to fb pin of the next xrp7618. if not used, leave it unconnected. iset 14 iset pin connect resistor r set from this pin to ground to set led channel current as per i channel =1.194x400/r set fb 15 fb pin samples the led cathode voltage on each channel and outputs the lowest voltage to the step-up converter. sdb 16 sdb output pin sdb signal is synchronous with the pwm signal during pwm dimming. it outputs low logic to the step-up converter under conditions such as shutdown or when all channels are inactive. sdbx 17 sdbx input pin used in parallel configuration as an interface terminal by connecting it to sdb pin of the next xrp7618. if not used, connect it to gnd. agnd 18 ground pin vcc 19 input voltage pin must be closely decoupled to gnd pin with a 0.1 f ceramic capacitor. en 20 enable pin this pin must be held high to enable the xrp7618. pgnd 5, 6 ground pin ep exposed pad exposed pad connect to ground ordering information part number temperature range marking package packing quantity note 1 note 2 xrp7618igb-f -40c t a +85c exar xrp7618igb yywwf xxxx tssop-20 bulk halogen free rohs compliant exposed pad XRP7618IGBTR-F 1.5k/tape & reel xrp7618evb xrp7618 evaluation board ?yy? = year ? ?ww? = work week ? ?x? = lot number, when applicable.
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 5/10 rev. 1.0.0 typical performance characteristics all data taken at v cc = 5v, r iset = 8k ? , t a = 25c, unless otherwise specified - schematic and bom from application information section of this datasheet. fig. 4: current per channel vs temperature fig. 5: pwm dimming: current per channel vs duty cycle fig. 6: current per channel vs input voltage fig. 7: current per channe l vs voltage per channel fig. 8: maximum output current vs voltage per channel fig. 9: current per chan nel vs rset resistor 0 2 4 6 8 10 12 14 16 18 20 0 20 40 60 80 100 current per channel (ma) duty cycle (%) 1khz 100hz 25khz 56 57 58 59 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 current per channel (ma) input voltage (v) 56 57 58 59 0.5 1.0 1.5 2.0 2.5 3.0 current per channel (ma) voltage per channel (v) 10 20 30 40 50 60 70 80 90 100 0 10203040 current per channel (ma) rset (k ? )
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 6/10 rev. 1.0.0 theory of operation the xrp7618 is an eight channel programmable constant current led driver capable of up to 100ma per channel. a single external resistor adjust s the current for each channel over a 10ma to 100ma range with tight matching between channels. dimming is supported through a standard pwm scheme or through an analog signal. furthermore, the xrp7618 maximizes the overall system efficiency by dynamically reporting the minimum led voltage necessary to remain in current regulation mode when used with a boost converter. multiple xrp7618s can be placed in parallel to drive over 8 strings of leds; however, unused channels should be tied to ground. built-in under voltage lo ck out, open led and over temperature protections insure safe operations under abnormal operating conditions. led c hannels c urrent s etting the maximum led current can be set up to 100ma per channel through the iset pin. to set the reference current i set , connect a resistor r set between this pin and ground. the value of r set can be calculated by the following formula: 1.194 this reference current is multiplied internally with a gain (k) of 40 0 then mirrored on all enabled channels. this sets the maximum led current, referred to as 100% current (i ledmax ). the value can be calculated by the following formula: or, 1.194 400 1.194 the led current can be reduced from 100% by pwm dimming control. pwm d imming c ontrol the led current can be adjusted by applying a pwm signal to the pwm pin. in this mode, all enabled channels are adjusted at the same time and brightness is adjusted from 1% to 100% of i ledmax . the supported external pwm signal frequency is 100hz to 25khz. a nalog d imming control besides pwm dimming control, the led current can be controlled continuously (from highest to lowest led current) by raising the voltage at the bottom of rset from 0v normally to 1v max, respectively. rset value may be determined as 1.194 400 where, 1.194v is a typical iset pin voltage, vmod is an adjustment voltage applied to the bottom side of rset, 400 is the typical current multiplication ratio, and i ledmax is the required led current per channel. fig. 10: xrp7618 analog dimming control if adjustment voltage vmod isn?t used, rset resistor should be connected to ground. s ystem p ower o ptimization the smart talk feature enables xrp7618 to maximize the overall system power efficiency, when used with a step-up converter, by dynamically reporting the minimum led channel voltage needed to maintain current regulation mode. the xrp7618 samples the voltage on each channel input and reports the lowest voltage of all st rings via the fb signal to the associated step up converter. if placed in shutdown through the en pin or if all channels are inactive, the xrp7618 outputs
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 7/10 rev. 1.0.0 a logic low to the converter via the sdb signal. furthermore, the sdb signal is synchronous to the pwm signal when pwm dimming is used. o pen led p rotection the xrp7618 provides a built-in protection for open led channel. upon detection of an open led channel event, the fb signal is driven low to allow the step-up converter to operate open loop which in turn raises the voltage on the remaining chx pins. upon reaching an internally pre-set threshold of 3v, the xrp7618 identifies the faulty channel and removes it from the control and reporting loop. at this point the fb signal resumes its normal function of repo rting the lowest led channel voltage and hence restores the proper operations of the converter. note that the open led channel is not disabled; however, its chx voltage is no longer reported. upon reconnection of the open led channel, current will be driven at the programmed level. p arallel m ode of o peration multiple xrp7618s can be placed in parallel to drive over 8 strings of leds; however, unused channels should be tied to ground. while the initial xrp7618 is connected to the step-up converter via its fb and sdb pins, the daisy chained xrp7618s are connected to each other through the respective fbx and sdbx pins. in this configurat ion, the initial xrp7618 reports the lowest led voltage and sdb signal of all the xrp7618s in pa rallel. refer to figure 12. typical application schematics fig. 11: single xrp7618 application
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 8/10 rev. 1.0.0 fig. 12: parallel operations with the xrp7618 fig. 13: single supply operations with the xrp7618
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 9/10 rev. 1.0.0 package specification 20-p in tssop (e xposed p ad ) unit: mm (inch)
x x r r p p 7 7 6 6 1 1 8 8 8 8 - - c c h h a a n n n n e e l l c c o o n n s s t t a a n n t t c c u u r r r r e e n n t t l l i i n n e e a a r r l l e e d d d d r r i i v v e e r r w w i i t t h h s s m m a a r r t t t t a a l l k k t t m m ? 2011 exar corporation 10/10 rev. 1.0.0 revision history revision date description 1.0.0 07/26/2011 initial release of datasheet for further assistance email: customersupport@exar.com exar technical documentation: http://www.exar.com/techdoc/default.aspx? e xar c orporation h eadquarters and s ales o ffices 48720 kato road fremont, ca 94538 ? usa tel.: +1 (510) 668-7000 fax: +1 (510) 668-7030 www.exar.com notice exar corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. exar corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and make s no representation that the circuits are free of patent infringement. charts and schedules contained here in are only for illustr ation purposes and may vary depending upon a user?s specific application. while the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. exar corporation does not recommend the us e of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause fa ilure of the life support system or to significantly affect it s safety or effectiveness. products are not authorized for use in such applications unless exar corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of exar corporation is adequately protected under the circumstances. reproduction, in part or whole, without the prior written consent of exar corporation is prohibited.
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