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description the a6262 is a linear, programmable current regulator providing up to 100 ma from each of four outputs to drive arrays of high brightness leds. the regulated led current from each output, accurate to 5%, is set by a single reference resistor. current matching in each string is better than 10% without the use of ballast resistors. driving leds with constant current ensures safe operation with maximum possible light output. output control is provided by an enable input, giving direct control for pwm applications, and by a debounced switch input, proving an on/off toggle action. optimum performance is achieved when driving 4 strings with 1 to 3 leds in each string, at a total current of up to 100 ma in each string. outputs can be connected in parallel or left unused as required. short detection is provided to protect the leds and the a6262 during a short-to-ground at any led output pin. the output will automatically resume the regulated current when the short is removed. a temperature monitor is included to reduce the led drive current if the chip temperature exceeds an adjustable thermal threshold. the device packages are a 10-pin msop (ly) and a 16-pin tssop (lp), both with exposed pad for enhanced thermal dissipation. they are lead (pb) free, with 100% matte tin leadframe plating. a6262-ds, rev. 4 features and benefits ? total led drive current up to 400 ma ? current shared equally up to 100 ma by up to 4 strings ? 6 to 50 v supply ? low dropout voltage ? led output short-to-ground and thermal protection ? on/off toggle switch input ? enable input for pwm control ? current slew rate limit during pwm ? current set by reference resistor ? automotive k-temperature range (?40c to 150c) applications: typical application diagram a6262 automotive led array driver ? dome light, map light, space lighting, mood lighting a6262 + ? la1 vin automotive 12 v power net pwm dimming input from lcu gnd la2 la3 la4 en sw on/off iref thth packages not to scale 10-pin msop with exposed thermal pad (suffix ly) 16-pin tssop with exposed thermal pad (suffix lp)
automotive led array driver a6262 2 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com absolute maximum ratings 1 characteristic symbol notes rating unit load supply voltage v in ?0.3 to 50 v pin en ?0.3 to 50 v pins la[1:4] ?0.3 to 50 v pins iref, thth, sw ?0.3 to 6.5 v ambient operating temperature range 2 t a k temperature range ?40 to 125 c maximum continuous junction temperature t j (max) 150 c transient junction temperature t tj over temperature event not exceeding 10 s, lifetime duration not exceeding 10 h, guaranteed by design characterization 175 c storage temperature range t stg ?55 to 150 c 1 with respect to gnd. 2 limited by power dissipation. selection guide part number ambient operating temperature, t a (c) packing package a6262klptr-t ?40 to 125 4000 pieces per 13-in. reel 16-pintssop with exposed thermal pad, 4.4 5 mm case A6262KLYTR-T ?40 to 125 4000 pieces per 13-in. reel 10-pin msop with exposed thermal pad 3 3 mm case thermal characteristics* may require derating at maximum conditions, see application information characteristic symbol test conditions* value unit package thermal resistance (junction to ambient) r ja lp package on 4-layer pcb based on jedec standard 34 oc/w on 2-layer pcb with 3.8 in. 2 of copper area each side 43 oc/w ly package on 4-layer pcb based on jedec standard 48 oc/w on 2-layer pcb with 2.5 in. 2 of copper area each side 48 oc/w package thermal resistance (junction to pad) r jp 2 oc/w *to be verified by characterization. additional thermal information available on the allegro ? website.
automotive led array driver a6262 3 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com la1 vin vbat current regulators gnd pad te m p comp te m p monitor slew limit current reference control logic la2 la3 la4 en sw iref r ref r th thth deglitch dq cq r functional block diagram pin-out diagrams lp package ly package thth iref gnd la1 la2 sw en vin la4 la3 1 2 3 4 5 10 9 8 7 6 pad nc nc thth iref gnd la1 la2 nc nc nc sw en vin la4 la3 nc 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 pad terminal list table name number function lp ly en 13 9 enable sw 14 10 switch input gnd 5 3 ground reference iref 4 2 current reference la1 6 4 led anode (+) connection 1 la2 7 5 led anode (+) connection 2 la3 10 6 led anode (+) connection 3 la4 11 7 led anode (+) connection 4 nc 1,2,8, 9,15,16 ? no connection; connect to gnd pad ? ? exposed thermal pad thth 3 1 thermal threshold vin 12 8 supply
automotive led array driver a6262 4 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com supply and reference v in functional operating range 2 6 ? 50 v v in quiescent current i inq la[1:4] connected to vin ? ? 10 ma v in sleep current i ins en = gnd, v in = 16 v ? ? 15 a startup time t on vin > 7 v to i la1 < ?5 ma, r ref = 125 51530 s current regulation reference voltage v iref 0.7 ma < i ref < 8.8 ma 1.15 1.2 1.25 v reference current ratio g h i lax / i ref ? 12.5 ? ? current accuracy 3 e ilax ?10 ma > i lax > ?100 ma ?5 4 5 % current matching 4 e imlax ?20 ma > i lax > ?100 ma, v lax match to within 1 v ? 5 10 % output current, high level i lax en = high ? g h i ref ?? i ref = 8 ma, en = high ?105 ?100 ?95 ma maximum output current i laxmax i ref = 9.2 ma, en = high ? ? ?110 ma minimum drop-out voltage v do v in ? v lax , i lax = ?100 ma ? ? 800 mv v in ? v lax , i lax = ?40 ma ? ? 660 mv current slew time current rising or falling between 10% and 90% 50 80 110 s logic inputs en and sw input low voltage v il ? ? 0.8 v input high voltage v ih 2?? v input hysteresis (en pin) v ihys 150 350 ? mv pull-down resistor (en pin) r pd ?50? k pull-up current (sw pin) i pu ? 100 ? a sw input debounce time t sw 10?50ms protection short detect voltage v scd measured at lax 1.2 ? 1.8 v short circuit source current i scs short present lax to gnd ?2 ?0.8 ?0.5 ma short release voltage v scr measured at lax ? ? 1.9 v short release voltage hysteresis v schys v scr ? v scd 200 ? 500 mv thermal monitor activation temperature t jm t j with i sen = 90%, thth open 95 115 130 c thermal monitor slope di sen /dt j i sen = 50%, thth open ?3.5 ?2.5 ?1.5 %/c thermal monitor low current temperature t jl t j at i sen = 25%, thth open 120 135 150 c overtemperature shutdown t jf temperature increasing ? 170 ? c overtemperature hysteresis t jhys recovery = t jf ? t jhys ?15? c 1 for input and output current specifications, negative current is defined as coming out of (sourcing) the specified device pin. 2 function is correct but parameters are not guaranteed outside the general limits (7 to 40 v). 3 when en = high, e ilax = 100 [( | i lax | r ref / 15 ) ?1], with i lax in ma and r ref in k . 4 e imla = 100 [ max ( | i lax ? i la(av) | ) / i la(av) ] , where i la(av) is the average current of all active outputs. electrical characteristics 1 valid at t j = ?40c to 150c, v in = 7 to 40 ; unless otherwise noted characteristics symbol test conditions min. typ. max. unit
automotive led array driver a6262 5 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com functional description the a6262 is a linear current regulator that is designed to pro- vide drive current and protection for parallel strings of series- connected high brightness leds in automotive applications. it provides up to four matched programmable current outputs, at up to 100 ma, with low minimum dropout voltages below the main supply voltage. for 12 v power net applications optimum performance is achieved when driving 4 strings of 1 to 3 leds, at currents up to 100 ma per string. the a6262 is specifically designed for use in internal illumina- tion applications where the led activity is controlled by a pwm signal, by a logic signal, or by a push-to-make, ground-connected switch. current regulation is maintained and the leds protected during a short to ground at any point in the led string. a short to ground on any regulator output terminal will disable that output until the short is removed. open load on any output will be ignored. integrated thermal management reduces the regulated current level at high internal junction temperatures to limit power dis- sipation. pin functions vin supply to the control circuit and current regulators. a small value ceramic bypass capacitor, typically 100 nf, should be con- nected from close to this pin to the gnd pin. gnd ground reference connection. should be connected directly to the negative supply. en logic input to enable led current output. this provides a direct on/off action and can be used for direct pwm control. the en input overrides the sw input when en is high. when en transitions from high to low, sw input logic is reset to off. sw logic input to toggle led current output on and off. a single push-to-make switch between sw and gnd will provide push-to-make/push-to-break, on/off toggle action. the sw input is debounced by typically 30 ms and is internally pulled to typi- cally 3 v, with approximately 100 a. iref 1.2 v reference to set current reference. connect resistor, r ref , to gnd to set reference current. thth sets the thermal monitor threshold, t jm , where the output current starts to reduce with increasing temperature. connecting thth directly to gnd will disable the thermal monitor function. la[1:4] current source connected to the anode of the first led in each string. connect directly to vin to disable the respective output. in this document ?lax? indicates any one of the four outputs. led current level the led current is controlled by four matching linear current regulators between the vin pin and each of the lax outputs. the basic equation that determines the nominal output current at each lax pin is: given en = high, i lax = r ref 15 (1) where i lax is in ma and r ref is in k . the output current may be reduced from the set level by the ther- mal monitor circuit. conversely the reference resistors may be calculated from: i lax = r ref 15 (2) where i lax is in ma and r ref is in k . for example, where the required current is 90 ma the resistor value will be: 90 == r ref 167 15 it is important to note that because the a6262 is a linear regu- lator, the maximum regulated current is limited by the power dissipation and the thermal management in the application. all current calculations assume adequate heatsinking for the dissi- pated power. thermal management is at least as important as the electrical design in all applications. in high current high ambient temperature applications the thermal management is the most important aspect of the systems design. the application section below provides further detail on thermal management and the associated limitations. operation with fewer led strings or higher currents the a6262 may be configured to use fewer than four led strings: by connecting outputs together for higher currents, by leaving the outputs open, or by connecting the output directly to vin to disable the regulator for that output.
automotive led array driver a6262 6 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com sleep mode when en is held low the a6262 will be in shutdown mode and all sections will be in a low power sleep mode. the input current will be typically less than 10 a. this means that the complete circuit, including leds, may remain connected to the power sup- ply under all conditions. safety features the circuit includes several features to ensure safe operation and to protect the leds and the a6262: ? the current regulators between vin and each lax output pro- vide a natural current limit due to the regulation. ? each lax output includes a short-to-ground detector that will disable the output to limit the dissipation. ? the thermal monitor reduces the regulated current as the tem- perature rises. ? thermal shutdown completely disables the outputs under ex- treme overtemperature conditions. short circuit detection a short to ground on any led cathode (figure 1a) will not result in a short fault condition. the current through the remaining leds will remain in regulation and the leds will be protected. due to the difference in the voltage drop across the leds, as a result of the short, the current match- ing in the a6262 may exceed the specified limits. any lax output that is pulled below the short detect voltage (fig- ure 1b) will disable the regulator on that output. a small current will be sourced from the disabled output to monitor the short and detect when it is removed. when the voltage at lax rises above the short detect voltage, the regulator will be re-enabled. a shorted led (figure 1c) will not result in a short fault condi- tion. the current through the remaining leds will remain in regulation and the leds will be protected. due to the difference in the voltage drop across the leds, as a result of the short, the current matching in the a6262 may exceed the specified limits. a short between leds in different strings (figure 1d) will not result in a short fault condition. the current through the remain- ing leds will remain in regulation and the leds will be pro- tected. the current will be summed and shared by the affected strings. current matching in the strings will then depend on the led forward voltage differences. temperature monitor a temperature monitor function, included in the a6262, reduces the led current as the silicon junction temperature of the a6262 increases (see figure 2). by mounting the a6262 on the same thermal substrate as the leds, this feature can also be used to limit the dissipation of the leds. a6262 la1 vin gnd la2 la3 la4 a6262 la1 vin gnd la2 la3 la4 a6262 la1 vin gnd la2 la3 la4 a6262 la1 vin gnd la2 la3 la4 a. any led cathode short to ground. current remains regulated in non-shorted leds. matching may be affected. b. any lax output short to ground. shorted output is disabled. other outputs remain active. c. current remains regulated. matching may be affected. only the shorted led is inactive. d. short between leds in different strings. current remains regulated. current is summed and shared by affected strings. intensity match dependent on voltage binning. figure 1. short circuit conditions.
automotive led array driver a6262 7 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com as the junction temperature of the a6262 increases, the regulated current level is reduced, reducing the dissipated power in the a6262 and in the leds. the current is reduced from the 100% level at typically 4% per degree celsius until the point at which the current drops to 25% of the full value, defined at t jl . above this temperature the current will continue to reduce at a lower rate until the temperature reaches the overtemperature shutdown threshold temperature, t jf . the temperature at which the current reduction begins can be adjusted by changing the voltage on the thth pin. when thth is left open the temperature at which the current reduction begins is defined as the thermal monitor activation temperature, t jm , and is specified, in the characteristics table, at the 90% current level. t jm will increase as the voltage at the thth pin, v thth , is reduced and is defined as approximately: 0.0039 = t jm (c) 1.46 ? v thth (3) a resistor connected between thth and gnd will reduce v thtii and increase t jm . a resistor connected between thth and a refer- ence supply greater than 1 v will increase v thth and reduce t jm . figure 3 shows how the nominal value of the thermal monitor activation temperature varies with the voltage at thth and with either a pull-down resistor, r th , to gnd or with a pull-up resis- tor, r th , to 3 v and to 5 v. in extreme cases, if the chip temperature exceeds the overtem- perature limit, t jf , all regulators will be disabled. the tempera- ture will continue to be monitored and the regulators re-activated when the temperature drops below the threshold provided by the specified hysteresis. note that it is possible for the a6262 to transition rapidly between thermal shutdown and normal operation. this can hap- pen if the thermal mass attached to the exposed thermal pad is small and t jm is increased to close to the shutdown temperature. the period of oscillation will depend on t jm , the dissipated power, the thermal mass of any heatsink present, and the ambient temperature. 100 80 60 40 20 0 t jm t jl t jf 90 25 70 90 110 junction temperature, t j (c) relative sense current (%) 130 150 170 figure 2. temperature monitor current reduction. 250 200 150 100 50 0 1.3 1.2 1.1 1.0 0.9 0.8 v thth 70 80 90 110 100 thermal monitor activation temperature, t jm (c) r th (k ) v thth (v) 130 120 150 140 r th pull-up to 5 v r th pull-up to 3 v r th pull-down to gnd figure 3. t jm versus a pull-up or pull-down resistor, r th , and v thth .
automotive led array driver a6262 8 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com application information power dissipation the most critical design considerations when using a linear regu- lator such as the a6262 are the power produced internally as heat and the rate at which that heat can be dissipated. there are three sources of power dissipation in the a6262: ? the quiescent power to run the control circuits ? the power in the reference circuit ? the power due to the regulator voltage drop the elements relating to these dissipation sources are illustrated in figure 4. quiescent power the quiescent power is the product of the quiescent current, i inq , and the supply voltage, v in , and is not related to the regulated current. the quiescent power, p q , is there- fore defined as: p q = v in i inq (4) reference power the reference circuit draws the reference current from the supply and passes it through the reference resis- tor to ground. the reference current is 8% of the output current on any one active output. the reference circuit power is the prod- uct of the reference current and the difference between the supply voltage and the reference voltage, typically 1.2 v. the reference power, p ref , is therefore defined as: p ref = r ref ( v in ? v ref ) v ref (5) regulator power in most application circuits the largest dis- sipation will be produced by the output current regulators. the power dissipated in each current regulator is simply the product of the output current and the voltage drop across the regulator. the total current regulator dissipation is the sum of the dissipa- tion in each output regulator. the regulator power for each output is defined as: p regx = ( v in ? v ledx ) i ledx (6) where x is 1, 2, 3, or 4. note that the voltage drop across the regulator, v reg , is always greater than the specified minimum drop-out voltage, v do . the output current is regulated by making this voltage large enough to provide the voltage drop from the supply voltage to the total forward voltage of all leds in series, v led . the total power dissipated in the a6262 is the sum of the quies- cent power, the reference power, and the power in each of the our regulators: p dis = p q + p ref + p rega + p regb + p regc + p regd (7) the power that is dissipated in each string of leds is: p ledx = v ledx i ledx (8) where x is a, b, c, or d, and v ledx is the voltage across all leds in the string. figure 4. internal power dissipation sources. a6262 lax i lax i inq i ref vin gnd iref r ref v ref v led v reg v in
automotive led array driver a6262 9 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com from these equations (and as illustrated in figure 5) it can be seen that, if the power in the a6262 is not limited, then it will increase as the supply voltage increases but the power in the leds will remain constant. dissipation limits there are two features limiting the power that can be dissipated by the a6262: thermal shutdown and thermal foldback. thermal shutdown if the thermal foldback feature is disabled by connecting the thth pin to gnd, or if the thermal resistance from the a6262 to the ambient environment is high, then the silicon temperature will rise to the thermal shutdown threshold and the current will be disabled. after the current is disabled the power dissipated will drop and the temperature will fall. when the temperature falls by the hysteresis of the thermal shutdown circuit, then the current will be re-enabled and the temperature will start to rise again. this cycle will repeat continuously until the ambient temperature drops or the a6262 is switched off. the period of this thermal shutdown cycle will depend on several electrical, mechanical, and thermal parameters, and could be from a few milliseconds to a few seconds. thermal foldback if there is a good thermal connection to the a6262, then the thermal foldback feature will have time to act. this will limit the silicon temperature by reducing the regulated current and therefore the dissipation. the thermal monitor will reduce the led current as the tempera- ture of the a6262 increases above the thermal monitor activation temperature, t jm , as shown in figure 6. the figure shows the operation of the a6262 with 4 strings of 3 red leds, each string running at 50 ma. the forward voltage of each led is 2.3 v and the graph shows the current as the supply voltage increases from 14 to 17 v. as the supply voltage increases, without the thermal foldback feature, the current would remain at 50 ma, as shown by the dashed line. the solid line shows the resulting current decrease as the thermal foldback feature acts. if the thermal foldback feature did not affect led current, the current would increase the power dissipation and therefore the silicon temperature. the thermal foldback feature reduces power in the a6262 in order to limit the temperature increase, as shown in figure 7. the figure shows the operation of the a6262 under the same conditions as figure 6. that is, 4 strings of 3 red leds, each string running at 50 ma with each led forward voltage at figure 5. power dissipation versus supply voltage. 3.0 2.5 2.0 1.5 1.0 0.5 0 a6262 power 70 80 90 110 100 supply voltage, v in (v) power dissipation, p d (w) 130 120 150 140 led power 4 strings v led = 6.9 v i led = 50 ma figure 6. led current versus supply voltage. figure 7. junction temperature versus supply voltage. 54 52 50 48 46 44 42 40 without thermal monitor with thermal monitor 14.0 14.5 15.0 16.0 17.0 15.5 supply voltage, v in (v) i led (ma) 16.5 4 strings v led = 6.9 v i led = 50 ma t a = 50c 130 125 120 115 110 105 100 without thermal monitor with thermal monitor 14.0 14.5 15.0 16.0 17.0 15.5 supply voltage, v in (v) t j (c) 16.5 4 strings v led = 6.9 v i led = 50 ma t a = 50c
automotive led array driver a6262 10 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com 2.3 v. the graph shows the temperature as the supply voltage increases from 14 to 17 v. without the thermal foldback feature the temperature would continue to increase up to the thermal shutdown temperature as shown by the dashed line. the solid line shows the effect of the thermal foldback function in limiting the temperature rise. figures 6 and 7 show the thermal effects where the thermal resistance from the silicon to the ambient temperature is 40c/w. thermal performance can be enhanced further by using a signifi- cant amount of thermal vias as described below. thermal dissipation the amount of heat that can pass from the silicon of the a6262 to the surrounding ambient environment depends on the thermal resistance of the structures connected to the a6262. the thermal resistance, r ja , is a measure of the temperature rise created by power dissipation and is usually measured in degrees celsius per watt (c/w). the temperature rise, t, is calculated from the power dissipated, p d , and the thermal resistance, r ja , as: t = p d r ja (9) a thermal resistance from silicon to ambient, r ja , of approxi- mately 30c/w (lp package) or 34c/w (ly package) can be achieved by mounting the a6262 on a standard fr4 double-sided printed circuit board (pcb) with a copper area of a few square inches on each side of the board under the a6262. multiple thermal vias, as shown in figure 8, help to conduct the heat from the exposed pad of the a6262 to the copper on each side of the board. the thermal resistance can be reduced by using a metal substrate or by adding a heatsink. supply voltage limits in many applications, especially in automotive systems, the avail- able supply voltage can vary over a two-to-one range, or greater when double battery or load dump conditions are taken into con- sideration. in such systems is it necessary to design the applica- tion circuit such that the system meets the required performance targets over a specified voltage range. to determine this range when using the a6262 there are two limiting conditions: ? for maximum supply voltage the limiting factor is the power that can be dissipated from the regulator without exceeding the temperature at which the thermal foldback starts to reduce the output current below an acceptable level. ? for minimum supply voltage the limiting factor is the maximum drop-out voltage of the regulator, where the difference between the load voltage and the supply is insufficient for the regulator to maintain control over the output current. minimum supply limit: regulator saturation voltage the supply voltage, v in , is always the sum of the voltage drop across the high-side regulator, v reg , and the forward voltage of the leds in the string, v led , as shown in figure 4. v led is constant for a given current and does not vary with supply voltage. therefore v reg provides the variable difference between v led and v in . v reg has a minimum value below which the regulator can no longer be guaranteed to maintain the output current within the specified accuracy. this level is defined as the regulator drop-out voltage, v do . the minimum supply voltage, below which the led current does not meet the specified accuracy, is therefore determined by the sum of the minimum drop-out voltage, v do , and the forward voltage of the leds in the string, v led . the supply voltage must figure 8. board via layout for thermal dissipation: (top) lp package (bottom) ly package.
automotive led array driver a6262 11 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com always be greater than this value and the minimum specified sup- ply voltage, that is: v in > v do + v led , and v in > v in (min) (10) as an example, consider the configuration used in figures 6 and 7 above, namely 4 strings of 3 red leds, each string running at 50 ma, with each led forward voltage at 2.3 v. the minimum supply voltage will be approximately: v in (min) = 0.55 + (3 2.3) = 7.45 v maximum supply limit: thermal limitation as described above, when the thermal monitor reaches the activation tempera- ture, t jm (due to increased power dissipation as the supply volt- age rises), the thermal foldback feature causes the output current to decrease. the maximum supply voltage is therefore defined as the voltage above which the led current drops below the accept- able minimum. this can be estimated by determining the maximum power that can be dissipated before the internal (junction) temperature of the a6262 reaches t jm . note that, if the thermal monitor circuit is disabled (by connect- ing the thth pin to gnd), then the maximum supply limit will be the specified maximum continuous operating temperature, 150c. the maximum power dissipation is therefore defined as: p d (max) = r ja ? t (max) (11) where t(max) is difference between the thermal monitor activa- tion temperature, t jm , of the a6262 and the maximum ambient temperature, t a (max), and r ja is the thermal resistance from the internal junctions in the silicon to the ambient environment. if minimum led current is not a critical factor, then the maxi- mum voltage is simply the absolute maximum specified in the parameter tables above. application examples operation with high-side pwm supply in some filament bulb replacement applications the supply may be provided by a pwm-driven high-side switch. the a6262 can be used in this application by simply connecting en to vin. the toggle action of the sw input will be reset to off at each power-up. in addition, in all cases when en is high, the en input will override the sw toggle status and enable the outputs. at the high-to-low transition of en, the sw toggle will always be reset to the off state. when power is applied, there will be a short startup delay, t on , before the current starts to rise. the rise time of the current will be limited by the internal current slew rate control. figures 9a to 9c show application circuit options, including a higher voltage supply, and combinations of outputs tied together and disabled. operation with both en and sw in some applications it may be required to utilize the functionality of both the en input and the sw input. for example in dome lighting, where a manual switch may be used to turn the light on and the lighting control unit may dim the light to off (see figure 10). in these cases it is important to understand the interaction of the two control inputs. ? in all cases, when en is high the en input will override the sw toggle status and enable the outputs. ? when en is low the sw input can be used to toggle the outputs on and off. ? the only time there is any interaction between the en input and the sw toggle is the high-to-low transition of en, where the sw toggle will always be reset to the off state. ? the sw toggle will also be reset to the off state at power-up.
automotive led array driver a6262 12 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com a6262 + ? la1 vin 12 v pwm high-side drive gnd la2 la3 la4 en sw iref thth a6262 + ? la1 vin automotive 24 v power net gnd la2 la3 la4 en sw iref thth a6262 + ? la1 vin automotive 12 v power net gnd la2 la3 la4 la1 la2 la3 la4 en sw iref thth on/off a6262 + ? vin automotive 24 v power net pwm dimming input from lcu gnd en sw iref thth on/off on/off figure 10. typical applications using sw and en together. figure 9. typical applications with various supply and output options. b. higher voltage operation c. mix of output combinations a. high brightness (hb) led incandescent lamp replacement
automotive led array driver a6262 13 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com package lp, 16-pin tssop with exposed thermal pad a 1.20 max 0.15 0.00 0.30 0.19 0.20 0.09 8o 0o 0.60 0.15 1.00 ref c seating plane c 0.10 16x 0.65 bsc 0.25 bsc 2 1 16 5.000.10 4.400.10 6.400.20 gauge plane seating plane a terminal #1 mark area b for reference only; not for tooling use (reference mo-153 abt) dimensions in millimeters dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown b c exposed thermal pad (bottom surface); dimensions may vary with device 6.10 0.65 0.45 1.70 3.00 3.00 16 2 1 reference land pattern layout (reference ipc7351 sop65p640x110-17m); all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and pcb layout tolerances; when mounting on a multilayer pcb, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference eia/jedec standard jesd51-5) pcb layout reference view c branded face 30.05 30.05
automotive led array driver a6262 14 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com package ly, 10-pin msop with exposed thermal pad terminal #1 mark area a gauge plane seating plane 0.86 0.05 seating plane 0.50 ref 0.25 2 1 10 2 1 10 a b 0.53 0.10 0.15 0.05 0.05 0.15 0 to 6 3.00 0.10 3.00 0.10 4.88 0.20 1.98 1.73 0.27 0.18 for reference only; not for tooling use (reference jedec mo-187) dimensions in millimeters dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown b exposed thermal pad (bottom surface)
automotive led array driver a6262 15 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com for the latest version of this document, visit our website: www.allegromicro.com copyright ?2009-2012, allegro microsystems, inc. allegro microsystems, inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per- mit improvements in the per for mance, reliability, or manufacturability of its products. before placing an order, the user is cautioned to verify that the information being relied upon is current. allegro?s products are not to be used in life support devices or systems, if a failure of an allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. the in for ma tion in clud ed herein is believed to be ac cu rate and reliable. how ev er, allegro microsystems, inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. revision history revision revision date description of revision rev. 4 january 13, 2012 update r ja

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