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16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 batt lx bst gnd vl cs otp ref up dn shdn sync ss cc csav mindac top view max1610 so m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s ________________________________________________________________ maxim integrated products 1 19-1128; rev 0; 9/96 evaluation kit available for free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 _______________ge ne ra l de sc ript ion the max1610/max1611 are fully integrated, high- efficiency drivers for cold-cathode fluorescent lam ps (ccfls). they operate from a 4.5v to 26v power source. an on-board, high-switching-frequency power mosfet reduces external component count and mag- netics size. the max1610/max1611 protect against open or shorted lamps. the ccfl can be driven from an isolated transformer secondary winding to improv e efficiency and avoid flicker at dim tube settings. brightness is adjusted by scaling the lamp current, or by operating with a fixed lamp current and chopping the ccfl on and off at a rate faster than the eye c an detect. the max1610s digital inputs increment, decrement, or clear an internal, 5-bit up/down counter, which set s ccfl brightness. the max1611 uses a system management bus (smbus) 2-wire serial interface to directly set ccfl brightness. both devices include micropower shutdown and a linear regulator that eli mi- nates the need for a separate logic supply. the dig ital interface remains active in shutdown, preserving th e brightness setting. ________________________applic a t ions notebook/laptop computers point-of-sale terminals portable medical equipment instrument displays ____________________________fe a t ure s ? direct digital control of ccfl brightness ? low supply current: 3ma max operating 20a max shutdown ? low-voltage operation, down to 4.5v ? internal 26v, 0.7 w power switch ? protection against open or shorted lamps ? supports isolated transformer secondarywinding ? smbus serial interface (max1611) ? no flicker at low brightness (internal 280hz current chopping) ? high power-to-light efficiency ? selectable 290khz/145khz switching frequency ? oscillator sync input ? 16-pin narrow so package 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 batt lx bst gnd vl cs otp ref sda scl smbsus sync ss cc csav mindac max1611 so ___________________________________________________ _______pin configura t ions part max1610 cse max1611 cse 0c to +70c 0c to +70c temp. range pin-package 16 narrow so 16 narrow so ______________orde ring i nform a t ion downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (t a = 0c to +70c, batt = 8.2v, mindac = 0v, unless ot herwise noted. typical values are at t a = +25c.) stresses beyond those listed under absolute maximu m ratings may cause permanent damage to the device . these are stress ratings only, and functional operation of the device at these or any other condi tions beyond those indicated in the operational sec tions of the specifications is not implied. exposur e to absolute maximum rating conditions for extended per iods may affect device reliability. batt to gnd ........................................ ....................-0.3v to 28v bst to gnd ......................................... .....................-0.3v to 30v bst to lx .......................................... ..........................-0.3v to 6v lx to gnd .......................................... ......-0.6v to (batt + 0.3v) vl to gnd.......................................... .........................-0.3v to 6v cs, csav, cc, sync, ref, mindac, ss, otp to gnd..................................... .......-0.3v to (vl + 0.3v) shdn , up, dn to gnd .................................... ...........-0.3v to 6v smbsus, sda, scl to gnd ............................ ..........-0.3v to 6v batt, lx current ................................... ..................................1a sda current ........................................ ................................50ma vl current ......................................... ..................................50ma continuous power dissipation (t a = +70c) so (derate 8.70mw/c above +70c) .................. .......696mw operating temperature range max1610cse/max1611cse.............................. 0c to +70c storage temperature range .......................... ...-65c to +160c lead temperature (soldering, 10sec) ................ .............+300c sync = ref sync = gnd or vl conditions % 89 91 power-switch maximum duty cycle v 4.0 sync input high voltage v 0.5 sync input low voltage m a -1 1 sync input current ns 200 batt = 25v sync low pulse width ns 200 sync high pulse width khz 240 350 oscillator sync pin synchronization range khz 125 145 165 4.75v < batt < 26v oscillator frequency 250 290 330 m a 10 no load lx switch off-leakage current w 0.7 1.0 i source = 100 m a batt-to-lx switch on-resistance switching regulator bst - lx = 4.1v batt input voltage range v 4.75 26 supply and reference sync = ref mv 62 0 sync = gnd ref load regulation v 1.92 2.0 2.08 ref output voltage v 3.0 3.6 4.75 vl output voltage, shutdown mode v 4.25 4.5 4.75 vl output voltage, operate mode ma 1.5 3 batt quiescent supply current, operate mode m a 10 20 batt quiescent supply current, shutdown mode units min typ max parameter ss = gnd m a 2.5 4.0 5.5 ss source current ss = 0.5v ma 2 ss sink current downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s _______________________________________________________________________________________ 3 electrical characteristics (continued) (t a = 0c to +70c, batt = 8.2v, mindac = 0v, unless ot herwise noted. typical values are at t a = +25c.) gnd < otp < vl guaranteed monotonic otp rising conditions max1610 logic levels mv 500 cs overcurrent cutoff threshold m a -1 1 otp input bias current mv -20 20 otp voltage trip point open and shorted tube protection m a 20 cc source current m a 80 d/a at full scale cc sink current m mho 85 csav to cc voltage-to-current converter transconductance cc = 2v, csav = 1v, d/a at 1lsb dac resolution bits 5 cc = 2v, csav = 1v, d/a at 1lsb dac and error amplifier m a -5 5 csav input bias current mv 232 247 260 cc = 2v, csav = 0v, d/a at full scale csav regulation point v 0 1.0 csav input voltage range v 3 mindac digital pwm threshold v 01 mindac input voltage range m a -1 1 mindac input bias current units min typ max parameter d/a at 1lsb 12 referred to ref v 0.8 shdn , up, dn input low voltage v 2.4 shdn , up, dn input high voltage m a -1 1 shdn , up, dn input bias current max1611 logic levels v 0.8 smbsus, sda, scl input low voltage v 2.2 smbsus, sda, scl input high voltage m a -1 1 smbsus, sda, scl input bias current v sda = 0.6v ma 6 sda output low sink current downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 4 _______________________________________________________________________________________ note 1: guaranteed by design. timing characteristicsmax1611 (figures 2 and 3, t a = +25c, unless otherwise noted.) (note 1) (note 1) conditions m s 1 t r scl, sca rise time m s 4.7 t low m s 4 t high scl serial clock high period scl serial clock low period ns 500 t su:dat sda valid to scl rising edge setup time, slave clocking in data m s 0.3 t f scl, sda fall time m s 4.7 t su:sta start condition setup time m s 4 t hd:sta start condition hold time units min typ max symbol parameter m s 1 t dv scl falling edge to sda valid, reading out data (note 1) ns 0 t hd:dat scl falling edge to sda transition timing characteristicsmax1610 (figure 1, t a = +25c, unless otherwise noted.) conditions m s 1 t 3 up, dn pulse separation m s 1 t 2 m s 1 t 1 up, dn pulse width high up, dn pulse width low m s 1 t 4 counter reset time units min typ max symbol parameter downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s _______________________________________________________________________________________ 5 1.0 0 batt supply current vs. batt voltage (shdn = vl) max1610/1611-toc2 batt (v) batt current (ma) 1.2 1.4 1.6 1.8 2.0 4 1216202428 8 shdn = vl, otp = 3v 0 0 batt supply current vs. batt voltage (shdn = ov) max1610/1611-toc5 batt (v) batt current ( m a) 2 4 6 8 10 4 1216202428 8 shdn = ov 2.0 0 vl output voltage vs. batt voltage (shdn = ov) max1610/1611-toc6 batt (v) vl (v) 2.5 3.0 3.5 4.0 4.5 5.0 4 1216202428 8 no load on vl, shdn = ov 2.0 0 vl output voltage vs. vl output current max1610/1611-toc3 vl output current (ma) vl voltage (v) 2.5 3.0 3.5 4.5 4.0 5.0 20 30 40 10 shdn = vl, otp = 3v batt = 12v batt = 5v 3.30 0 vl output voltage vs. vl load current max1610/1611-toc4 vl load current ( m a) vl voltage (v) 3.35 3.40 3.45 3.50 3.55 3.65 3.60 3.70 400 800 600 1000 200 shdn = gnd batt = 12v batt = 5v 1.5 1 ref output voltage vs. ref output current max1610/1611-toc1 ref output current (a) ref output voltage (v) 1.6 1.7 1.8 1.9 2.0 2.1 2.2 10 100 1000 10000 shdn = vl, batt = 5v 2.0 0 vl output voltage vs. batt voltage (shdn = vl) max1610/1611-toc7 batt (v) vl (v) 2.5 3.0 3.5 4.0 4.5 5.0 4 1216202428 8 no load on vl, shdn = vl __________________________________________typic a l o pe ra t ing cha ra c t e rist ic s (t a = +25c, unless otherwise noted.) downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 6 _______________________________________________________________________________________ max1610 max1611 name 1 up pin 1 sda 2 dn 8 8 mindac 7 7 csav 6 6 cc 2 scl 13 13 gnd 12 12 vl 11 11 cs 10 10 otp 9 9 ref function logic-level input. a rising edge on up increments t he 5-bit counter for the 5-bit dac. up = dn = 1 presets the counter to mid-scale. system management bus serial data input and open-dr ain output logic-level input. a rising edge on dn decrements t he 5-bit counter for the 5-bit dac. up = dn = 1 presets the counter to mid-scale. the voltage at mindac sets the dacs minimum-scale output voltage. tying mindac to vl enables the internal 280hz current-chopping mode . input to the voltage-to-current converter, which av erages the voltage on csav using the capacitor on cc. output of the voltage-to-current converter; input t o the pwm comparator, which sets the current limit. a capacitor placed at cc sets the cu rrent-regulator-loop bandwidth. system management bus serial clock input system ground output of the internal linear regulator. vl can be overdriven by a voltage greater than 4.75v to operate the chip from +5v 5%, and to conserve p ower. bypass with 0.1 m f to gnd. low-side current-sense input. the current-mode regu lator terminates the switch cycle when the voltage at cs exceeds ref - cc. open-tube protection comparator. as long as otp exc eeds the reference voltage, the n-channel batt-to-lx switch is forced off. 2.0v reference output. bypass with 0.1 m f to gnd. ___________________________________________________ ___________pin de sc ript ion 14 14 bst power input to the high-side gate driver, which swi tches the internal n-channel mosfet on and off. 15 15 lx ground connection for the internal high-side gate d river; source-connection point for the internal n-channel mosfet 16 16 batt 4.5v to 25v battery-voltage input point. connects t o the internal n-channel power mosfets drain, and to the input of the internal linear regu lator that powers the chip. 3 shdn 3 smbsus 4 4 sync 5 5 ss logic-level shutdown input pin. applying a logic lo w to shdn places the chip in a low- supply-current shutdown mode. system management bus suspend mode input. smbsus se lects one of two chip- configuration settings, which are preprogrammed ser ially. oscillator synchronization input. tying sync to ref sets the oscillator frequency to 290khz. tying sync to gnd or vl lowers the oscillator frequ ency to 145khz. soft-start pin. a 4a current source feeds the capa citor placed on ss. the voltage on this pin limits the peak current in the switch. when the lamp is turned off, ss pulls to gnd. downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s _______________________________________________________________________________________ 7 t 3 t 1 up dn t 2 t 4 t su:sta t su:dat t su:dat t hd:dat t hd:dat t hd:sta scl start condition a5 clocked into slave a4 clocked into slave a3 clocked into slave most significant address bit (a6) clocked into slave sda t low t high ? ? ? ? figure 1. max1610 up and dn signal timing figure 2. max1611 smb serial-interface timingaddr ess downloaded from: http:///
_______________de t a ile d de sc ript ion ge t t ing st a rt e d a cold-cathode fluorescent lamp (ccfl) has two term i- nals. for the ccfl to emit light, the two lamp term inals must be driven with a high-voltage (approximately 550v ac rms) and high-frequency (approximately 45khz) sine wave. the max1610/max1611 use a vary- ing dc input voltage to create this high-voltage, h igh- frequency sine-wave drive. to select the correct component values for the max1610/max1611 circuit, several ccfl parameters and the minimum dc input voltage must be specified; these are listed in tabl e 1. table 3 shows the recommended component values to use with the circuit of figure 4, depending on the par- ticular ccfl parameters. the c2 values in table 3 have been selected such that the normal operating voltage on the secondary of t1 is as close as possi ble to the ccfl strike voltage (where the strike voltag e (v s ) is assumed to be approximately 1.8 times the ccfl operating voltage (v l )). components t1, c1, r2, q1, and q2 form a royer oscillator. a royer oscillator is a resonant tank c ircuit that oscillates at a frequency dependent on c1, the pri- mary magnetizing inductance of t1 (l p ), and the impedance seen by the t1 secondary. the max1610/max1611 regulate the current fed into the royer oscillator by sensing the voltage on r1. for a given current through the royer oscillator (i r1 ), the power delivered to the ccfl depends on the royer oscillator frequency. the r1 values in table 3 have been selected to ensure that the power into the ccf l does not exceed its maximum rating, despite t1, c1, and c2 component-value variations. the royer oscillator waveforms for the circuit of figure 4 are shown in figures 5 and 6. ana log circ uit ry the max1610/max1611 maintain fixed ccfl bright- ness with varying input voltages on batt by regulat ing the current fed into the royer oscillator. this cur rent is sensed via resistor r1 between csav and gnd. an internal switch from batt-to-lx pulse-width modulat es at a fixed frequency to servo the csav pin to its r egula- tion voltage. the csav regulation voltage can be adjusted via the digital interface to set ccfl brig ht- ness. the max1610 and max1611 differ only in the digital interface they use to adjust the internal 5 -bit digi- tal-to-analog converter (dac) that sets the csav re gu- lation voltage. the minimum-scale (min-scale) csav regulation voltage is resistor adjustable using the min- dac pin, setting the minimum ccfl brightness. the d/a setting at max1610/max1611 power-up is preset to mid-scale (10000 binary) (figure 7). mindac sets the minimum scale the mindac pin sets the lowest ccfl brightness level. the voltage at mindac is divided by eight, a nd sets the minimum csav regulation voltage. for exam- ple, in the circuit of figure 4, r5 (150k ) and r6 (51k ) form a resistor divider from ref, which sets mindac to 507mv (ref = 2.0v). this sets a minimum csav regulation voltage of 63mv with a full-scale csav regulation voltage of 247mv. m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 8 _______________________________________________________________________________________ t dv t dv scl rw bit clocked into slave acknowledged bit clock into master most significant bit clocked slave pulling sda low sda ? ? ? ? figure 3. max1611 smb serial-interface timingackn owledge downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s _______________________________________________________________________________________ 9 c9 c4 c3 c8 r5 r6 batt ss cc sync ref mindac gnd csav cs otp lx bst vl d2 r3 r4 d1 c5 max1610 max1611* c2 ccfl c1 r1 r2 6 5 34 2 1 10 q2 q1 v in 12 14 15 10 11 7 13 4 6 5 16 + 9 8 c7 l1 t1 c6 d3 r7 * digital interface not shown table 1. necessary ccfl specifications once a ccfl has been struck, the voltage required t o maintain light output falls to approximately 550v rms . small tubes may operate on as little as 250v rms . the operating voltage of the ccfl stays relatively constant, even as the tubes brightness is varied. although ccfls typically operate at 550v rms, a higher voltage is required initially to light up the tube. ccfl minimum strike voltage (kick-off voltage) ccfl typical operating voltage (lamp voltage) description specification v l v s symbol v rms v rms units i l ma rms the maximum root-mean-square ac current through a c cfl is almost always 5ma rms. no dc current is allowed through any ccfl. ccfl maximum operating current (lamp current) f l khz the maximum ac-lamp-current frequency. ccfl maximum frequency (lamp frequency) v min v the minimum dc input voltage to the max1610/max1611 circuit determines the turns ratio required for the dc-ac c onversion transformer. decreasing the minimum input voltage i ncreases the size of the transformer required for a given ou tput power. dc power source minimum input voltage figure 4. typical floating-lamp application circuit downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 10 ______________________________________________________________________________________ toler- ance working voltage c1 20% 25v c2 10% 3kv symbol c3, c5 20% 25v c4, c6, c7, c8 -20% 25v c9 -50% 35v 0.1 m f (note 1) (pf) value 27nf 0.1 m f 10 m f b) capacitors c) other components notes d f 0.001 @ 1khz high voltage ceramic, larger values acceptable tantalum, low esr generic part surface-mount part q1, q2 2n2222a fmmt619, sot23 d1, d3 1n4148 cmpd4448, sot23 symbol d2 1n5818 ec10qs04 l1 cdr125-101 manufacturer zetex central t1 ctx110605 nihon sumida coiltronics 1a npn switching transistor, v ceo 3 50v 50ma silicon diode, v br 3 40v description 1a schottky diode, v br 3 30v 100h, 1a inductor 6w royer oscillator transformer, turns ratio 67:1, secondary (pins 10 and 6) : primary (pins 1 and 3), primary magnetizing inductance (l p ) of 44h 20% note: component values depend on lamp characteristics. se e table 3 to select values. note: f roy = royer oscillator damped resonant oscillation freq uency. t1 primary magnetizing inductance (l p ) = 44h 20%. vct = average voltage from the t1 center tap to the emitters of q1 and q2 (ignoring q1, q2 v ce,sat ). c1 = 0.1f 20%; c2 = 10% tolerance; r1 = 1% tole rance. table 3. selecting circuit values for figure 4 table 2. typical application circuit component values tolerance power rating r1 1% 1/8w r2 10% 1/8w r3 5% 1/16w r4 5% 1/16w r7 10% 1/16w r6 5% 1/16w r5 5% 1/16w (note) 510 w value 51k w 8.2k w 20 w 51k w 150k w symbol 600 5 53.6 63.1 78.1 0.698 w 8.41v 15pf min typ max vct (v max ) 7.29v 7.17v 6.55v 4.14v 3.63v 3.61v 4.30v c2 18pf 18pf 20pf 36pf 22pf 43pf 18pf i l (ma rms ) f roy (khz) 550 5 52.5 61.8 76.7 500 5 52.1 61.0 75.1 450 5 51.1 59.7 73.3 300 5 45.6 52.8 64.7 250 250 3 50.3 58.6 71.8 5 43.3 49.7 60.3 300 3 52.1 61.0 75.1 r1 0.665 w 0.715 w 0.732 w 0.681 w 1.21 w 0.715 w 1.18 w v l (v rms ) a) resistors downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s ______________________________________________________________________________________ 11 6v -1a 5s/div 0v 1a t1 center-tap voltage c1 current batt = 10v, i batt = 0.20a, mindac = 0.5v, d/a value = 11111 figure 4 circuit, c2 = 15pf, i r1 = 462ma, ccfl vl = 500v rms 3v 0v 10ms/div 0v 6v ss voltage t1 center-tap voltage figure 4 circuit, c2 = 15pf, r1 = 545 w , ccfl vl = 500v rms , batt = 15v, mindac = 0.5v, d/a value = 10000 figure 5. royer oscillator typical operating wavefo rms for circuit of figure 4 figure 6. start-up waveforms for circuit of figure 4 mid-scale ref / 8 = 250mv full-scale min-scale = mindac / 8 omv dac code csav regulation voltage note: dac code 00000 forces the batt-to-lx switch o ff regardless of csav or mindac voltage. 00000 00001 00010 00011 00100 00101 00110 00111 01000 01001 01010 01011 01100 01101 01110 01111 10000 10001 10010 10011 10100 10101 10110 10111 11000 11001 11010 11011 11100 11101 11110 11111 figure 7. csav regulation voltage range downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 12 ______________________________________________________________________________________ figure 8. transformer primary/secondary voltage rel ationship t1 primary center-tap voltage (pin 2) t1 secondary voltage (pin 10pin 6) 2 p w p v ct 2 2 p w n p v ct 2 -n p v ct 2 note: v ct = average voltage from the t1 center to the emitte rs of q1 and q2 (ignoring q1, q2 v ce, sat ). w = 2 p f roy . open-tube protection (otp) any real transformer used in a royer oscillator wil l have a maximum-allowed secondary voltage. if the maximum- allowed secondary voltage is exceeded, the winding insulation can break down, leading to permanent tra ns- former damage. the maximum-allowed secondary volt- age can be exceeded either when the ccfl drive circ uit is turned on without the ccfl being in place, or wh en the ccfl becomes disconnected during normal opera- tion due to a mechanical failure. to protect agains t these fault conditions, use the otp pin to sense the volt age on the transformer center tap (pin 2 of figure 4). whe never the voltage on otp exceeds the ref reference voltag e, the batt-to-lx power switch is forced off. for example, in figure 4, the ctx110605 transformer has a maximum-allowed continuous secondary voltage of 1340v rms. d1 and c5 detect the peak voltage on the center tap of t1. r3 and r4 determine the limit on the center tap peak voltage. the relationship betwe en the voltage on the center tap of t1 and the seconda ry voltage is diagrammed in figure 8. neglecting the q1/q2 saturation voltage and the voltage on the r1 current-sense resistor yields equation 1: where v sec is the maximum root-mean-square voltage allowed on the secondary, n is the secondary-to-pri ma- ry turns ratio, and v ctpk is the peak voltage on the transformer center tap. bloc k dia gra m of t he ana log se c t ion figure 9 shows a functional diagram of the analog c ir- cuitry in the max1610/max1611. the chips have ident i- cal analog circuitry, and differ only in their digi tal interface. loop-compensation capacitor (cc) the batt-to-lx switch turns on at fixed frequency, and turns off when the current-sense voltage on the cs pin exceeds cc - ref. as the cc pin voltage rises, the cs current limit rises as well. a transconductance amp lifier compares the voltage on csav to the desired regulat ion voltage and outputs a current proportional to this error to the cc pin. a capacitor from cc to gnd sets the bandwidth of this regulation loop, as shown in equa tion 2: where bw is the bandwidth of the csav regulation lo op in khz, and c3 is the capacitance from cc to gnd in nf. soft start (ss) soft start prevents the triggering of otp upon powe r- up. placing a capacitor from ss to gnd soft starts the royer oscillator by slowly raising the cs current-l imit voltage. internal circuitry pulls ss to gnd during power-on reset, or whenever the lamp is turned off (dac = 00000, shutdown mode, on-1 = 0, or on-0 = 0) (figures 10 and 11). when ss is not pulled to gnd, a n internal 4a current sources into the capacitor at the ss pin. this pin is internally diode clamped to ref so that it rises to a maximum voltage of about 2.7v. regardless of the voltage on cc, the cs current-sen se voltage is never allowed to exceed the voltage on s s divided by 5. frequency selection and synchronization the sync pin performs two functions: it sets the b att- to-lx switching frequency, and it allows the batt-t o-lx switching frequency to be synchronized to an extern al oscillator. sync tied to gnd or vl sets a 145khz switching frequency; sync tied to ref sets a 290khz bw = 85 2c3 p v = v2 2n ctpk sec downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s ______________________________________________________________________________________ 13 osc 5-bit dac + 2.0v - 8 level shifter 4.5v reg vl gnd dmos power switch 5 digital interface up (sda) dn (scl) shdn (smbsus) r s 4a q (note) mindac sync ss otp ( ) are for max1611 note: circuitry to detect mindac = vl not shown. s ee chopping the lamp current section. 5 ref cc csav cs lx bst batt gm ?? s figure 9. functional diagram downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 switching frequency. any rising edge on sync restar ts a batt-to-lx switch cycle by forcing the switch on. ________m ax 1 6 1 0 digit a l i nt e rfa c e the max1610 contains an internal 5-bit up/down coun ter that sets the value of the internal 5-bit dac. at p ower-on, or when both the up and dn pins are held high simul ta- neously, the 5-bit up/down counter is preset to 100 00 binary, which corresponds to mid-scale. a rising ed ge on up increments the 5-bit up/down counter. a risin g edge on dn decrements the 5-bit up/down counter. th e counter will not roll over on either underflow or o verflow. for example, if the ccfl is at maximum intensity le vel, rising edges on up will not change the output. the shdn pin provides a way to lower the max1610 supply current to 10a without resetting the 5-bit up/down counter. with shdn = 1, the max1610 oper- ates normally with vl at 4.5v. when the batt-to-lx power switch operates, an additional 3ma of current (other than the supply current) is consumed through the bst pin, requiring vl to source at least 4.5ma of current. with shdn = 0, all analog circuitry turns off, except for a coarse regulator that can source up to 500a from vl. the coarse regulator preserves the state of the internal logic and keeps the digital i nterface active during shutdown ( shdn = 0). ________m ax 1 6 1 1 digit a l i nt e rfa c e a single byte of data written over the intel system management bus (smbus?) controls the max1611. figures 10 and 11 show example single-byte writes. the max1611 contains two 7-bit latches for storing conf igu- ration data. only one of the 7-bit latches is activ e at a time. the max1611 responds only to its own address, 0101101 binary. the smbsus pin selects which of the two sets of configuration data is used. figure 12 s hows a schematic diagram of the max1611s digital circui try. notice that the smbsus pin selects which one of the digit a lly cont rolle d ccfl ba c k light pow e r supplie s 14 ______________________________________________________________________________________ start condition most significant address bit least significant address bit slave pulls sda low slave pulls sda low regsel d4-0 stdby-0 shdnb-0 d3-0 d2-0 d1-0 d0-0 slave acknowledge slave acknowledge most significant data bit least significant data bit scl sda r/w bit start condition most significant address bit least significant address bit slave pulls sda low slave pulls sda low regsel d4-1 stdby-1 shdnb-1 d3-1 d2-1 d1-1 d0-1 slave acknowledge slave acknowledge most significant data bit least significant data bit scl sda r/w bit figure 10. max1611 serial-interface single-byte wr ite example (regsel = 0) figure 11. max1611 serial-interface single-byte wr ite example (regsel = 1) downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s ______________________________________________________________________________________ 15 multiplexer y shdnb stdby ss circuitry bias generators clr otpok ref vl otp otp comparator r s q pre 5-bit dac d_ smbsus a s b y = a when s is low 7 7 7 5 8 7 7-bit latch-0 le 8-bit shift register control logic otpok scl sda in data le 7-bit latch-1 le figure 12. max1611 serial-interface circuitry bloc k diagram downloaded from: http:///
name description 7 regsel register select. a zero in this bit writes the rema ining seven bits into the 7-bit latch-0 (figure 13). 6 shdnb-0 complete shutdown. pulling smbsus low with shdnb-0 = 0 places the max1611 into a low-quiescent-current shutdown mode, with the refer ence off and the vl linear-regulator output switched to a low-current, coarse regulation mode. pulling smbsus low with shdnb-0 = 1 puts the max1611 into its normal operat ional mode, with the reference and internal vl linear regulator fully on. shdnb-0 supe rsedes stdby-0. as long as shdnb-0 = 0 and smbsus = 0, it doesn't matter what stdby-0 is; the max1611 still shuts down. bit 5 stdby-0 standby, disables ccfl supply only. as long as smbs us stays low and stdby-0 = 0, the internal power switch is kept off and ss is held sh orted to gnd; neither the internal refer- ence nor the linear regulator is affected. with std by = 1 and smbsus low, the max1611 operates normally. 4 3 2 1 0 d4-0 d3-0 d2-0 d1-0 d0-0 dac input data. with the smbsus pin low, bits d4-0 through d0-0 set the dac. table 4. max1611 configuration byte with regsel = 0table 5. max1611 configuration byte with regsel = 1 por state* 0 0 1 0 0 0 0 * initial register state after power-up. * initial register state after power-up. m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s 16 ______________________________________________________________________________________ name description 7 regsel register select. a one in this bit writes the remai ning seven bits into the 7-bit latch-1 (figure 13). 6 shdnb-1 complete shutdown. pulling smbsus high with shdnb-1 = 0 places the max1611 into a low-quiescent-current shutdown mode, with the refer ence off and the vl linear regulator output switched to a low-current coarse regulation mode. pulling smbsus high with shdnb-1 = 1 puts the max1611 into its normal operat ional mode, with the reference and internal vl linear regulator fully on. shdnb-1 supe rsedes stdby-1. as long as shdnb-1 = 0 and smbsus = 0, it doesnt matter what stdby-1 is; the max1611 still shuts down. bit 5 stdby-1 standby, disables ccfl supply only. as long as smbs us stays high and stdby-1 = 0, the internal power switch is kept off and ss is hel d shorted to gnd; neither the internal ref- erence nor the linear regulator is affected. with s tdby-1 = 1 and smbsus high, the max1611 operates normally. 4 3 2 1 0 d4-1 d3-1 d2-1 d1-1 d0-1 dac input data. with the smbsus pin high, bits d4-1 through d0-1 set the dac. por state* 1 1 1 0 0 0 0 downloaded from: http:///
two 7-bit registers is used. tables 4 and 5 describ e the data format for the configuration data. status information can be read from the max1611 using the smbus read-byte protocol. figure 13 shows an example status read. table 6 describes the statu s information data format. during shutdown (smbsus = 0 and shdnb-0 = 0, or smbsus = 1 and shdnb-1 = 0), the max1611 serial interface remains fully functional and can be used to set either the shdnb-0 or shdnb-1 bits in order to retu rn the max1611 to its normal operational state. _______ chopping t he la m p curre nt chopping the lamp current allows lower sustainable light levels without lamp flicker. intensity is varied by control- ling the on-time duty cycle. tying mindac to vl act i- vates a special mode, which allows the ccfl intensi ty to be varied by turning the lamp on and off at a frequ ency faster than the eye can detect. the ss pin pulls to gnd during off time and rises to 2.7v during on time. d uring on time, the csav pin regulates to ref / 8 (250mv). during off time, the batt-to-lx power switch is for ced off and the cc compensation node goes high imped- ance. omit r5, r6, and c4 of the circuit in figure 4. in this mode, leave ss floating and increase the cc capacitance to 0.1f. also, insert a 330 resistor in series with d1 (figure 4) to prevent the open-lamp detecti on cir- cuit from being tripped by the repeated striking of the lamp. the ss pin will oscillate at the switching fr equency divided by 1024 (283hz with sync = ref). the intens ity can be varied with the duty cycle at the ss pin. th e duty cycle is set by the dac in 3% increments. duty cycl e will vary with intensity. full-scale yields a 100% duty cycle. dac codes 00001, 00010, and 00011 all yield the m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s ______________________________________________________________________________________ 17 figure 13. max1611 serial-interface read example start condition most significant address bit least significant address bit slave pulls sda low otpok max1611 drives sda da4 da3 da2 da1 da0 slave acknowledge most significant data bit scl sda r/w bit * initial register state after power-up. table 6. max1611 status bits name function 7 otpok latched open-tube detection. otpok = 0 indicates th at open-tube detection has been triggered. as soon as the voltage on the otp pin ex ceeds ref, the otpok bit is cleared. reset the otpok pin by entering shutdown or standby . 6 5 unused. these bits always return a logic one. bit 4 3 2 1 0 da4 da3 da2 da1 da0 displays the dac setting selected by smbsus. por state* 1 downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 minimum 9% duty cycle. dac code 00000 shuts off the lamp entirely (0% duty cycle). figure 14 shows the chopped waveforms with the dac set to mid-scale. __________ applic a t ions i nform a t ion dire c t ly re gula t ing t he la m p curre nt the max1610/max1611 can directly regulate the ccfl current by tapping into the secondary of t1 (figure 15). this allows more precise setting of the maximum lam p current (i l ). the disadvantage of this approach is that the secondary-to-ground voltage is twice that shown in figure 4, increasing the likelihood of the thermome ter effect, where one end of the lamp is brighter than the other. figure 15 uses the same component values as figure 4, except for r1, r40, d40, and d41. d40 and d41 are the same type of diode as d1. r1 should be 0.68 w 10% to set a peak current limit of about 735ma. use a 107 w 1% resistor for r40 to set a lamp current of 5ma rms . this circuit accepts a wide range of lamp types without component adjustments. com pone nt supplie rs table 7 lists three different sources for c1. c1 re quires a low dissipation factor to prevent overheating as energy is cycled between c1 and the t1 magnetizing induc- tance in the royer resonant tank. table 8 lists sup pliers for the high-voltage ballast capacitor, c2. digit a lly cont rolle d ccfl ba c k light pow e r supplie s 18 ______________________________________________________________________________________ 4v 0v 0v 500 m s/div 15v ss voltage t1 center-tap voltage batt = 15v, mindac = vl, ss = open, cc = 0.1 m f, c2 = 15pf, mid-scale setting, d/a value = 10000 figure 14. chopped waveforms figure 15. directly regulating the ccfl current c9 c4 c3 c8 r5 r6 batt ss cc sync ref mindac gnd csav cs otp lx bst vl d2 r3 r4 d1 d40 r40 d41 c5 max1610 max1611 c2 ccfl c1 r1 r2 6 5 34 2 1 10 q2 q1 vin 12 14 15 10 11 7 13 4 6 5 16 + 9 8 c7 l1 t1 c6 d3 r7 downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s ______________________________________________________________________________________ 19 table 7. capacitor c1 supplier informationtable 8. capacitor c2 supplier information ___________________chip i nform a t ion transistor count : 5457 5-70-11-51 (0621) 8785-0 914-347-2474 206-883-9200 phone dissipation factor (tan d ) at 1khz and 20c 0.008. 58-06-84-74 wima smd7.3104 (0621) 8710457158 914-347-7230 dissipation factor (tan d ) at 1khz 0.002. 206-881-6959 paccom electronics chev0025j104 notes/contact fax supplier part vancouver, wa olean, ny hong kong germany location 206-695-5836 206-696-2840 716-372-6316 716-372-6611 852-765-8185 852-363-3303 avx/kyocera 1808ha330katma 08131 9004-44 08131 9004-0 fax phone supplier part hong kong germany elmsford, ny redmond, wa location valencia, ca 805-295-5920 dissipation factor (tan d ) at 1khz and 20c 0.0015. 805-295-5928 novacap 4040n104m250 smyrna, ga 404-436-3030 404-436-1300 germany 49-911-6687193 49-911-66870 taiwan 886-2-536-6721 886-2-562-4218 murata ghm1040sl330j3k old bridge, nj 908-679-3222 908-679-3366 metuchen capacitors, inc. 302c1812a330k sylmar, ca 818-364-6100 818-364-9800 johanson dielectrics 302r29n330k downloaded from: http:///
m ax 1 6 1 0 /m ax 1 6 1 1 digit a lly cont rolle d ccfl ba c k light pow e r supplie s maxim cannot assume responsibility for use of any c ircuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the cir cuitry and specifications without notice at any tim e. 20 __________________m a x im i nt e gra t e d produc t s, 1 2 0 sa n ga brie l drive , sunnyva le , ca 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0 ? 1996 maxim integrated products printed usa is a reg istered trademark of maxim integrated products. maxim cannot assume responsibility for use of any c ircuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the cir cuitry and specifications without notice at any tim e. 20 __________________m a x im i nt e gra t e d produc t s, 1 2 0 sa n ga brie l drive , sunnyva le , ca 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0 ? 1996 maxim integrated products printed usa is a reg istered trademark of maxim integrated products. maxim cannot assume responsibility for use of any c ircuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the cir cuitry and specifications without notice at any tim e. 20 __________________m a x im i nt e gra t e d produc t s, 1 2 0 sa n ga brie l drive , sunnyva le , ca 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0 ? 1996 maxim integrated products printed usa is a reg istered trademark of maxim integrated products. ___________________________________________________ _____pa c k a ge i nform a t ion dim a a1 b c e e h l min 0.053 0.004 0.014 0.007 0.150 0.228 0.016 max 0.069 0.010 0.019 0.010 0.157 0.244 0.050 min 1.35 0.10 0.35 0.19 3.80 5.80 0.40 max 1.75 0.25 0.49 0.25 4.00 6.20 1.27 inches millimeters 21-0041a narrow so small-outline package (0.150 in.) dim d d d min 0.189 0.337 0.386 max 0.197 0.344 0.394 min 4.80 8.55 9.80 max 5.00 8.75 10.00 inches millimeters pins 8 14 16 1.27 0.050 l 0-8 h e d e a a1 c 0.101mm 0.004in. b downloaded from: http:///

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