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L482 november 1991 hallCeffect pickup ignition controller . direct driving of the external po- wer darlington . coil current charging angle (dwell) control . coil current peak value limitation . continuous coil current protection . conduction and desaturation time output signals . permanent conduction protection reset output signal . overvoltage protection for exter- nal darlington . load dump protection description the L482 is an integrated circuit designed for use with an npn darlington in breakerless ignition sy- stems with hall-effect pickup sensors and high ener- gy ignition coils. it controls the energy stored in the ignition coil and the desaturation time of the external darlington to limit the power dissipation. dip16 ordering numbers : L482 (dip16) L482d1 (so16) pin connections (top views) dip16 so16 the L482 is also particularly suitable for use as igni- tion control and driving stage in more sophisticated car electronic systems which employ microproces- sor circuits. so16 1/11
block diagram (*) thermal resistance junction-aluminia with the device soldered on the middle of an aluminia supporting substrate measuring 1 5 x 20mm ; 0.65mm thickness with infinite heatsink. absolute maximum ratings symbol parameter value unit v r reverse battery voltage C 14 v v d dump voltage 100 v p tot power dissipation at t amb = 90 c so16 dip 1.2 0.65 w w t j , t stg junction and storage temperature range C 55 to 150 c thermal data symbol parameter value unit r th j-amb thermal resistance junction-ambient ( dip16 ) max 90 c/w r th j-al thermal resistance junction-alumina ( so16 ) max 50 c/w L482 2/11
pin functions (refer to fig. 3 for dip16 package) n name function 1 conduction time signal a low level on this output signal indicates when the external darlington is in the on condition i.e. when the current flows through the coil (ton in fig.1) 2 hall-effect input hall-effect pickup input. a high level on this pin enables the current driving into the coil. the effective coil charge will be a function of the dwell control logic. a high to low transition from the hall-effect pickup is the signal for ignition actuation. the input signal, supplied by the open collector output stage of the hall-effect sensor, has a duty cycle typically about 70%. 3 dwell control the average voltage on the capacitor c 2 connected between this pin and ground depends on the motor speed and the voltage supply. the comparison between v c2 and v c5 voltages determines the timing for the dwell control. the recommended value is 100nf using a 100k w resistor at pin 7. for the optimized operation of the device, c2 = c5. 4 dwell control timer the capacitor c5 connected between this pin and ground is charged when the hall-effect output is high and is discharged at the high to low transition of the hall-effect signal. the recommended value is 100nf using a 100k w resistor at pin 7. 5 hall sensor supply this pin can be used to project the hall-effect pickup against the voltage transients, the resistor r a limits the current into the internal zener. 6 desaturation time signal open collector output signal. this output is high when the external darlington is in desaturation condition (current limitation), see t d pulse in fig. 1. 7 reference voltage a resistor r11 connected between this pin and ground sets the internal current used to drive the external capacitors of the dwell control (c 2 and c 5 ) and permanent conduction protection (c 1 ). the recommended value is 100k w . 8 permanent conduct. protection timer a capacitor c1 connected between this pin and ground determines the intervention delay of the permanent conduction protection, t pc of the figure 2. with a 1 m f capacitor and 100k w resistor r 11 at pin 7 the typical delay is 1s. 9 permanent conduct. reset output (no available in micropackage) (*) a low pulse on this output detects the intervention of the permanent conduction protection, as shown in figure 2. typically the duration of the time t r is more than 100 m s. 10 current sensing input (*) connection for coil current limitation. the current is measured on the sense resistor r s and divided on r 1 /r 2 . the current limitation value is given by : i sens = v sens r1 + r2 r s r2 11 dump protection (*) the device is protected against the load dump. in load dump condition an internal circuit, based on a zener diode and a darlington transistor, switches off the external darlington and short circuits the supply. by means of the external divider r8/r9 the protection threshold can be changed and is given as first approximation by: v dth = 8.5 ? ? r 8 + r 9 r 9 ? ? + 5 10 - 4 r 8 (the resistor r9 value must be higher than 4k w ). 12 power supply (*) supply voltage input. a 7v (typ) zener is present at the input. the external resistor r 7 limits the current through the zener for high supply voltages. L482 3/11
(*) these pins refer only to the dip package type. for the so 16 version the permanent conduction reset output signal is not available and the pin 9 becomes the c urrent sensing input. pin 10 replaces the pin 11 function, pin 11 becomes the power supply input and pin 12 is used as the signal ground. electrical characteristics (v s = 14 v, C 40 c t j 125 c referred to application circ uit of figure 3 regarding dip-16 package version) symbol parameter test conditions min. typ. max. unit v s operating supply voltage 6 28 v i s supply current v 12 = 4.5v 25 ma v z zener voltage (pin 12) i z = 80ma 6.5 8.8 v v i sensor input (pin 2) low voltage high 2.5 0.5 v v i i sensor input current (pin 2) v i = low v s = 6 to 16v C12 C1 ma v hz hall-cell supply zener voltage (pin5) i hz = 10ma 19 22 25 v i hz hall-cell supply zener current (pin5) t = 10ms t amb = 25 c 100 ma v ce sat (v 14 Cv 16 ) series darlington driver sat. voltage i o = 70ma i o = 150ma 0.4 0.6 1.0 v v v sens current limit. sensing voltage (pin10) v s = 6 to 16v 200 400 mv i 3d i 3c i 3c /i 3d c2 discharge current c2 charge current v s = 6 to 16v (*) note 1 0.2 5 6 3.4 20 35 m a m a v ovz external darlington overvoltage protection zener voltage i ovz = 5ma to 15ma t amb = 25 c 25 30 35 v v 7 reference voltage 2.5 3.5 v t d desaturation time f = 40hz v s = 14v 0.6 1.2 1.57 ms pin functions (continued) n name function 13 ground this pin must be connected to ground. 14 driver collector the collector current for the internal driver which drives the external darlington is supplied through this pin. the external resistor r 10 limits the dissipation in the ic. the value of the resistor depends is a function of the darlington used and on the limiting current in the coil. 15 overvoltage limitation the external is protected against overvoltage by means of an internal zener available at this pin. the external divider r 5 /r 6 defines the limitation value, given as first approximation by: v ovp = ? ? 30 r 5 + 5 10 - 3 ? ? r 6 + 30 16 driving stage output current driver for the external darlington. to ensure stability and precision of tdesat c 3 and r 3 must be used. recommended value for r3 is 2k w in order not to change the open loop gain of the system. r c may be added to c 3 to obtain greater flexibility in various application situations. c 3 and rc values ranges are 1 to 100nf and 5 to 30k w depending on the external darlington type. L482 4/11
electrical characteristics (continued) symbol parameter test conditions min. typ. max. unit t pc permanent conduction protection time (pin 8) (see fig. 2) v i = h c i = 1 m f 135s v 1 charging angle output voltage low high i sink = 0 i sink = 1ma i source = 1.5ma i source = 2.5ma 3 5 0.5 1.2 v v v v v 6 desat. time output low voltage i 6 (sink) = 0.5ma 0.7 v i 6l desat. time leakage current (pin6) v 6 = 5v 10.5 m a i 9l permanent conduction reset leakage current (pin9) v 9 = 5v 10.5 m a figure 1 : main waveforms. application information L482 5/11
figure 2 : low frequency condition and permanent conduction protection. figure 3 : application circuit (dipC16). L482 6/11
figure 4 : application circuit (soC16). circuit operation the L482 control the conduction time (dwell) and the peak value of the primary current in the coil over the full range of operating conditions. the coil current is limited to a predetermined level by means of a negative feedback circuit including a current sensing resistor, a comparator, the driver stage and the power switch. the dwell control circuit maintains the output stage in its active region during current limitation. the time the output stage is in the active region (desaturation time) is sufficient to compensate for possible varia- tions in the nergy stored due to the acceleration of the motor ; moreover this time is limited to avoid ex- cessive power dissipation. control of the dwell angle (fig. 1 and 4) the dwell angle control circuit calculates the con- duction time d for the output transistor in relation to the speed of rotation, to the supply voltage and to the characteristic of the coil. on the negative edge of the hall-effect input signal the capacitor c 2 begins discharging with a constant current i 3d . when the set peak value of the coil cur- rent is reached, this capacitor charges with a con- stant current i 3c = 13.3 x i 3d and the coil current is kept constant by desaturating the driver stage and the external darlington. the capacitor c 5 starts charging on the positive edge of the hall-effect input signal with a constant current i 4c . the dwell angle, and consequently the starting point of the coil current production, is decided by the com- parison between v c2 and v c5 . a positive hysteresis is added to the dwell comparator to avoid spurious effects and c 5 is rapidly discharged on the negative edge of hall-effects input signal. in this way the average voltage on c 2 increases if the motor speed decreases and viceversa in order to maintain constant the ratio td at any motor speed. t td is kept constant (and not d = cost) to control the power dissipation and to have sufficient time to avoid low energy sparks during acceleration. the charging time d C td depends on the coil and the voltage supply. desaturation times in static condi- tions.in static conditions, if c 2 = c 5 as recommen- ded and if the values of the application circuit of fig. 3, 4 are used. td 1 = t1 + i 3c /i 3d L482 7/11
desaturation times in low and high fre- quency operation. due to the upper limit of the voltage range of pin 3, if the components of fig. 3, 4 are used, below 10hz (300rpm for a 4 cylinder en- gine) the off time reaches its maximum value (about 50ms) and then the circuit gradually loses the control of the dwell angle because d = t C 50ms over 200hz (6000rpm for a 4 cylinder engine) the available time for the conduction is less than 3.5ms. if the used coil is 6mh, 6a, the off time is reduced to zero and the circuit loses the dwell angle control. transient response. the ignition system must deliver constant energy even during the con- dition of acceleration and deceleration of the motor below 80hz/s. these conditions can be simulated by means of a signal generator with a linearly mo- dulated frequency between 1hz and 200hz (this corresponds to a change between 30 and 6000rpm for a 4 cylinders engine. current limit. the current in the coil is monito- red by measuring the i sense current flowing in the sensing resistor r s on the emitter of the external dar- lington. i sense is given by : i sense = i coil + i 16 when the voltage drop across r s reaches the inter- nal comparator threshold value the feedback loop is activated and i sense kept constant (fig. 1) forcing the external darlington in the active region. in this con- dition : i sense = i coil when a precise peak coil current is required r 5 must be trimmed or an auxiliary resistor divider (r 1 , r 2 ) added : v sens r 1 icpeak (a) = ( + 1) r s r 2 protection circuit permanent conduction protection the battery voltage is applied to ignition module by means of the ignition key. in these conditions, with the motor stopped, it is necessary that there is no permanent conduction in the ignition coil irrespecti- ve of the polarity of the input signal. the L482 incorporates a timing circuit to implement this protection ; the duration of the intervention is set by means of a capacitor c 1 at pin 8 = 1 m f, and r 11 = 100k w , when the input signal is high for more than 1 s, the coil current gradually decreases down to zero to avoid spurious sparks (see fig. 2). this timing allows normal operation of the module above 30rpm. darlington overvoltage limitation the darlington is protected against overvoltage by means of an external divider r 5 /r 6 (pin 15) and an internal zener. this zener drives the external darlin- gton in order to limit the collector voltage. reverse battery prtotection. due to the presence of external impedance at pin 5, 10, 11, 14, 15, L482 is protected against reverse battery volt- age. dump protection. the load dump protection withstands up to 100v with a decay time 300ms. the intervention thre- shold for load dump is fixed by means of an external divider connected to pin 11 (dip-16 package ver- sion) or to pin 10 using a micropackage type. negative spike protection.if correct opera- tion is requested also during short negative spikes, the diode ds and capacitor c s must be used. use of the ic electronic advance sy- stem when the device is digitally controlled the control unit transmits a suitable input signal to the power module, receiving in turn information that allows the control of the dwell and the on time of the final tran- sistor. for this reason L482 provides the following outputs : . a time signal equal to the time in which the final darlington is in the active region i.e. when the coil current is limited (v ds ) as shown in figure 1. this signal must be ttl compatible. . a ttl compatible output from the timing circuit (v rs in figure 2). this pulse, available only using the dip-16 package version is present after the protection against cranking transients. . a time signal equal to the time in which the final darlington, is in "on" condition (v on ) i.e. when the current flows through the coil, see fig. 1. other application information if the supply voltage is disconnected - or the battery wire is broken - while the current is flowing through the coil, the external diode d 1 keeps the coil current from recirculating into the device : in this way both device and darlington are protected. L482 8/11
dip16 package mechanical data dim. mm inch min. typ. max. min. typ. max. a1 0.51 0.020 b 0.77 1.65 0.030 0.065 b 0.5 0.020 b1 0.25 0.010 d 20 0.787 e 8.5 0.335 e 2.54 0.100 e3 17.78 0.700 f 7.1 0.280 i 5.1 0.201 l 3.3 0.130 z 1.27 0.050 L482 9/11
so16 package mechanical data dim. mm inch min. typ. max. min. typ. max. a 1.75 0.069 a1 0.1 0.2 0.004 0.008 a2 1.6 0.063 b 0.35 0.46 0.014 0.018 b1 0.19 0.25 0.007 0.010 c 0.5 0.020 c1 45 (typ.) d 9.8 10 0.386 0.394 e 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 8.89 0.350 f 3.8 4.0 0.150 0.157 l 0.5 1.27 0.020 0.050 m 0.62 0.024 s8 (max.) L482 10/11
information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences of use of such information nor for any inf ringement of patents or other rights of third part ies which may result from its use. no license is granted by impl ication or otherwise under any pat ent or patent rights of sgs-thomson microelectronics. specifica- tions mentioned in t his publication are subject to change without noti ce. this publication supersedes and replaces all information pre- viously supplied. sgs-thomson microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of sgs-thomson microelec tronics. ? 1994 sgs-thomson microelectronics - all rights reserved sgs-thomson microelectronics group of companies aust ralia - brazil - france - germany - hong kong - i taly - j apan - korea - malaysia - malta - morocco - the netherlands - sin gapore - spain - sweden - switzerland - taiwan - thaliand - united k ingdom - u.s.a. L482 11/11

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