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telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 1 (11) automotive lamp outage monitor description the U2481B and the u2482b multicomparator circuits are designed to monitor automotive illumination by sensing the voltage drop across shunt resistors. provided with extremely low comparator thresholds, these ics can be used together as a chip set to build an entire lamp monitor system. single operation of both circuits is also possible. as a special feature for brake lamp monitoring, the U2481B contains a latch stage connected to one of its triple comparators. with 4 single comparators 1 double comparator and 2 triple comparators each of the integrated circuits monitors up to 12 lamps and up to 6 fuses. all comparator stages are combined together to control the common output stage. features extremely low comparator thresholds of typically 3.5 mv internal compensation for copper shunts internal compensation for voltage-dependent bulb characteristic comparator input voltage may exceed supply voltage internal protection measures for pulses according to iso tr 7637/1 esd according to mil-sid-883 c test method 3015.7 human body model: 4 kv machine model: 200 v emi protection (tem cell up to 100 v/m) benefits extremely low threshold voltage gives low voltage drop via shunt resistor. power dissipation of the lamp monitor module is minimized perfect emc in conjunction with an appropriate pc board layout applications both ics can be used in any kind of vehicle with a 12 v supply. it is sufficient to insert small resistors into the lamp wiring and to provide the dashboard instrument cluster with a pilot lamp. these ics increase the safety and add comfort features.
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 2 (11) block diagram ref k2 e1 ref k3 e1 e2 e3 ref k5 e1 e2 voltage drift of comparator threshold i t = f (v b ) power on reset stabilized voltage v stab = 5.2 v clock 1 2-t osc clock 2 20-t osc ref k4 e1 ref k7 e1 e2 e3 start forward start return high at counter end high at counter zero up down counter t = 1.2 s cl 2 cl 1 start forward start return high at counter end high at counter zero up down counter t = 1.2 s cl 2 cl 1 28 ref k1 set reset out oscillator v b por v s v s v b divider latch for stoplamps out reset set por cl 1 cl 2 k6 ref e1 3.5 mv v s 3.5 mv 3.5 mv 3.5 mv 3.5 mv 13 mv k1 13 mv ref e1 26 1 2 7 6 8 9 24 25 16 4 3 5 23 11 10 12 13 27 in 1k1 ref k2 in 1k2 ref k3 in 1k3 in 2k3 in 3k3 in fk3 ref k4 in 1k4 in fk5 ref k5 in 1k5 in 2k5 in f ref k7 in 1k7 in 2k7 in 3k7 v b v s 20 19 15 14 17 22 21 18 osc out in fk6 ref k6 in 1k6 gnd 94 8833 i t i t + + i t * connection to gnd only for u2482b (latch disabled * figure 1.
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 3 (11) pin description 94 8831 ref k2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 in 1k2 in 1k5 ref k5 in 2k5 in 1k3 ref k3 in 2k3 in 3k3 in 1k7 ref k7 in 2k7 in 3k7 out ref k1 in 1k1 in fk3 in 1k4 ref k4 in f ref k6 in 1k6 v b v s gnd in fk6 in fk5 osc figure 2. pin configuration pin symbol function 1 ref k2 reference for threshold voltage single comparator k2 2 in 1k2 input 1; single comparator k2 3 in 1k5 input 1; double comparator k5 4 ref k5 reference for threshold voltage; double comparator k5 5 in 2k5 input 2; double comparator k5 6 in 1k3 input 1; triple comparator k3 7 ref k3 reference for threshold voltage; triple comparator k3 8 in 2k3 input 2; triple comparator k3 9 in 3k3 input 3; triple comparator k3 10 in 1k7 input 1; triple comparator k7 (U2481B with latch) 11 ref k7 reference for threshold voltage; triple comparator k7 (U2481B with latch) 12 in 2k7 input 2; triple comparator k7 (U2481B with latch) 13 in 3k7 input 3; triple comparator k7 (U2481B with latch) 14 out output for pilot lamp 15 osc r/c combination for oscillator 16 in fk5 fuse monitor input ; double comparator k5 17 in fk6 fuse monitor input; single comparator k6 18 gnd ground 19 v s supply voltage 20 v b reference voltage of compara- tors 21 in 1k6 input1; single comparator k6 22 ref k6 reference for threshold voltage; single comparator k6 23 in f input; brake fuse comparator 24 ref k4 reference for threshold voltage; single comparator k4 25 in 1k4 input 1; single comparator k4 26 in fk3 fuse monitor input; triple comparator k3 27 in 1k1 input 1; single comparator k1 28 ref k1 reference for threshold voltage; single comparator k1
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 4 (11) 27 28 2 k 1 k fuse 16 2 k 4 1 k 3 2 k shunt 5 2 k shunt 20 19 15 f c 1 0.1 f c 2 r 2 1000 r 1 v b v s 150 v batt 15 osc 14 out r osc 82 k c osc 10 nf kl 61 pilot lamp 1.2 w out a b 95 10689 U2481B u2482b a: example of a asingle comparatoro using the fuse as a shunt resistor b: example of a adouble comparatoro using copper shunts and additional fuse monitoring figure 3. basic application diagram
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 5 (11) functional description power supply, pins 19 and 20 the ics have two supply pins. the ic itself is supplied via pin 19 (stabilized voltage, por-circuitry). pin 20 supplies only the current sources of the comparators. both pins have an an internal 21 v zener diode for protection. for reasons of interference protection and surge immunity the supply voltage pins have to be provided with rc-circuitries as shown in figure... the resistors limit the current in the case of overvoltage, whereas the capacitors smooth the supply voltage. recommended values: pin 19: r = 150 ; k = 0.1 f pin 20: r = 1000 ; k = 0.1 f an external diode protects the ic against battery reversal. power-on-reset when the supply voltage is switched on, a power-on-reset pulse is generated internally which resets the brake lamp monitor latch and the counter stages. oscillator, pin 15 the rc-oscillator is the time base for clock 1 and clock 2 (see block diagram) which are desired from a divider stage and fed to the two upward and downward counters. the oscillator frequency f osc is mainly determined by the external r/c components and an integrated resistor. the capacitor k is charged by the external resistor and discharged by the integrated one. because of the temper- ature characteristic and the tolerances of the integrated 2 k -resistor, the external one has to have considerable higher value in order to achieve a stable frequency. calculation of the frequency: f osc 1 f osc 1 c osc (0.74 r osc 2260 ) with the recommended values r osc = 82 k and c osc = 10 nf f osc 1.58 khz comparators comparators k1 and k2 : threshold voltage of typically v th = 13 mv; designed to monitor high- and low-beam bulbs, where the fuses can be used as shunt resistors. comparators k3 to k7: threshold voltage of typically v th = 3.5 mv; designed for all other monitor purposes. due to the integrated compensation circuitry, these comparators are suitable for pc layer copper shunts. a bulb is detected as agoodo as long as the voltage drop via the shunt resistor exceeds the threshold voltage. the pilot lamp is off. a failed bulb is detected if the voltage drop via the shunt resistor is smaller than the threshold voltage. the pilot lamp is on. an external transistor is necessary to drive the pilot lamp. in order to disable monitoring when the lamps are switched off, therefore the comparator outputs are disabled if the reference voltage v ref < v min with v min = 0.33 v b . as protection against transients on the supply, all comparator inputs require external resistors. their tolerances directly influence the comparator threshold accuracy. resistors with a 1% tolerance are recommended. single comparators : the inputs (k1, k2, k4, k6) sink currents of typically 10 a each. during switch-over, the currents of reference and input pins are identical. therefore identical external protection resistors (r = 1 k ) are required. double comparator : the reference input (k5) sinks a current of typically 20 a; its inputs sink currents of typically 10 a each during switch-over. therefore the external protection resistors must provide r = 1 k for ref k5 and r = 2 k each for in 1k5 and in 2k5 . triple comparators : the reference inputs (k3 and k7) sink currents of typically 30 a. all inputs (in 1k3 , in 2k3 in 3k3, and in 1k7 , in 2k7 , in 3k7 ) sink the identical typical current of 10 a during switch-over. therefore the external protection resistor must provide r = 1 k for ref k3 and ref k7 and r = 3 k at each input. fuse monitoring the internal exor conjunction of comparators k1 and k2 allows fuse monitoring for both lamps. even a simultaneous blowout of both fuses is detected. the pins in fk3 , in fk5 and in fk6 with their exor gates can be used for additional fuse monitoring. detection threshold for a blown fuse is v ref < v min with v min = 0.33 v b (v b = reference voltage of comparators). pin in f is used for brake fuse monitoring. with a voltage drop v f > 4.8 v across the fuse, the comparator detects a blown fuse. a voltage drop v f < 2.8 v represents a agoodo fuse. U2481B's comparator k7 is connected to a latch, thus a brake lamp outage is memorized.
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 6 (11) integrated delay, debouncing, failure dis- play as soon as a comparator detects a failure a slow upward counter is started in order to generate the delay time, t del = 1.2 s. with a consistent failure the output stage is enabled after t del . if the failure disappears during t del a fast downward counter is started in order to generate the reset time t reset 135 ms. the upward counter is reset, the output stage stays disabled. benefits: intermittent contacts in the wire harness do not activate the pilot lamp! even cyclical intermittent contacts are screened out as long as the pulse/pause ratio is smaller than 10:1. in the case of higher duty cycles the upward counter may reach its trigger threshold for the output activation after t > t del . individual delay- and reset times can be adjusted with external r/c components according to (see aoscillatoro) t del = 1930 x t osc t reset = 198 x t osc latch for brake lamp monitor a failure of a brake lamp detected by comparator k7 or a blown fuse in the brake circuitry is memorized after the delay time has expired. a reset of the latch can only be performed with a apower- on-reseto. output stage the output is a darlington stage stage with protection diodes to v s and ic ground. the output is designed to drive an external pilot lamp with an external pnp transistor. at the end of the delay time the output stage is switched on and can source a current of i out = 10 ma with a typical saturation voltage of v sat = 1 v. test mode with v test = 23 v (20 ma) applied to pin osc, via a 200 resistor the delay time stage can be bypassed for test purposes. a failure detection will be displayed immediately to save time during threshold testing.
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 7 (11) application hints layout recommendations for copper layer shunts lamp outage monitor systems can be produced most cost- efficiently if stamped shunt resistors are replaced by copper layer shunts which are generated with the pc board layout. the U2481B and the u2482b are suitable for this application because of their comparator thresholds, which are compensated in reference to the temperature characteristic of copper. a constant lamp current, i lamp = v th /r sh with threshold voltage v th = f(t) and shunt resistor r sh = f(t), is achieved if the comparator threshold and the shunt resistor have identical temperature characteristics. with the temperature coefficient of copper a cu = 3.9 10 3 1/k, a copper shunt changes its nominal value by 52% if the automotive ambient temperature range of t amb = 40 to +95 c is taken into consideration. examples for sheet resistances of copper shunts (t amb = 25 c): r a = 0.5 m /square (35.1 m layer thickness) r a = 0.25 m /square (70 m layer thickness) how to lay out copper shunts (figure 3) the width of the copper trace has to be selected in reference to a low current-effected temperature increase. the copper trace must be capable of peak currents which do not blow the fuse. the peak currents are specified by the car manufacturers. example: a 7.5 a fuse allows a peak current of 26 a (1 s), 15 a (10 s) or 10 a (60 s). the copper shunt length has to be calculated between the two sense connections to the comparator. the connection of the common reference input of double and triple comparators has to be considered carefully. calculation example for a copper shunt used with a 4 w bulb. i lamp = 0.325 a failure criterion: i = 1/2 i lamp 10 a fuse is capable of i = 13.5 a copper layer thickness: 70 m comparator threshold voltage (U2481B, u2482b): v th = 3.5 mv assumed copper width for temperature increase t cu < 50 c: w cu = 2.5 mm (13.5 a, 70 m) two equations for calculation of the shunt resistance: r shunt = r a l/w cn (with r a = cu sheet resistance) r shunt = v th / 1/2 i lamp thus the length of copper shunt is calculated as: l = 2 v th w cn / r a i lamp l = 215 mm for a reasonable pc-layout a meander-shaped shunt resistor is recommended. the high lamp currents may cause hot spots at sharp edges of the copper shunts. that may deteriorate accuracy of the measurement. therefore it is recommended to layout the copper shunts with smoothed curves. in accordance to figure...the meander may be formed by 4 straight tracks (length l s each) and 3 connecting 180 ares (length l are each). if the mean are radius is selected to r = w cn the are lenght becomes l are = w cn . thus the total lenght is l= 4 l s + 3 l are = 4 l s + 3 w cn with l = 215 mm the track length becomes l s 1 4 (l 3 w cn ) l s = 47.8 mm using fuses as shunt resistors this cost saving method can be used if the following assumptions are fulfilled: each lamp needs a dedicated fuse the fuse socket is mounted within the monitor module to connect the sense linesare suitable for this monitor task because of their comparator thresholds are compensated for the fuse temperature coefficient of a f = 4.1 10 3 1/k calculation example for a 55 w bulb and a 7.5 a fuse: measured voltage drop across the fuse: v f = 52 mv measured current: i lamp = 4.2 a calculated resistance: r f = 12.4 m selected comparatore threshold: v th = 1/4 v f = 13 mv (typically); with a lamp current i lamp < v th /r f =< 1.05 a the comparator detects a blown fuse.
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 8 (11) 94 8832 1 234 5 67 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 U2481B u2482b w cn = 2.5 mm to lamp switch to lamp r1 r2 w cn l s l arc figure 4. design example for a copper shunt with meander shape absolute maximum ratings parameters symbol value unit supply voltage v s , v batt 16.5 v pulse current (2 ms) i s 1.1 a short circuit current (reversed battery) i sc 170 ma output current i out 12 ma junction temperature t j 150 c thermal resistance parameters symbol value unit thermal resistance so 28 r thja 110 k/w ambient temperature range t amb 40 to +100 c storage temperature range t stg 55 to +125 c
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 9 (11) electrical characteristics t amb = 40 to +100 c, v batt (kl. 15) = 10 to 15 v, supply series resistors and input protection rsistors connected (see figure 1 ablock diagramo and figure 2 abasic application schematico) unless otherwise specified. parameters test conditions / pins symbol min. typ. max. unit supply operating voltage v batt 9 16 v supply current v batt = 13 v, v 14 = low pin 20 pin 19 0.3 3 0.7 5 1.1 7 ma ma power on reset (por) t amb = 25 c pin 19 v batt (kl. 15) 3.0 3.7 4.2 5.0 v v comparators comparator input current during switch over v batt = 13 v pins 27, 28 pins 1, 2 pins 24, 25 pins 21, 22 pin 7 pins 6, 8, 9 pin 11 pins 1012 pin 4 pins 3,5 i 27 , i 28 i 1 , i 2 i 24 , i 25 i 21 , i 22 i 7 i 6 , i 8 , i 9 i 11 i 10 ,i 11 ,i 12 i 4 i 3 , i 5 10 10 10 10 30 10 30 10 20 10 a comparator thresholds v t1 of comparators k1 and k2 (v t1 = v ref... v in... ) v s = 10 v pins 1, 2, 27, 28 v s = 13 v v s = 15 v v t1x x = pin no. 8.5 10.0 11.0 11.5 13.0 14.0 14.5 16.0 17.0 mv voltage characteristic v t1 0.5 mv/v temperature characteristic t t1 3900 ppm/ k comparator thresholds v t2 of comparators k3 to k7 (v t2 = v ref... v in... ) pins 6, 7, 8, 9 pins 24, 25 pins 3, 4, 5 pins 21, 22 pins 10, 11, 12 v s = 10 v v s = 13 v v s = 15 v v t1x x = pin no. 1.5 2.0 2.3 3.0 3.5 3.8 4.5 5.0 5.3 mv voltage characteristic v t2 0.17 mv/v temperature characteristic t t2 3900 ppm/ k min. comparator input voltage for detection all ref-pins v min 0.33 v batt output output current v batt = 13 v pin 14 i 14 10.0 ma output saturation voltage i out = 10 ma pin 19pin 14 v sat 1.0 1.5 v
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 10 (11) unit max. typ. min. symbol test conditions / pins parameters protection voltage of zener diodes pin 19 pin 20 all ref... and in... pins v s v b v ref... , v in... 21 19 19 v oscillator oscillator frequency r osc = 82 k , c osc = 10 nf, pin 15 f osc 1.58 khz delay time r osc = 82 k , c osc = 10 nf t d 1.1 1.2 1.3 s debounce time r osc = 82 k , c osc = 10 nf t db 115 125 135 ms break fuse brake fuse detection threshold v batt pin 23 v tb 2.8 3.8 4.8 v input current v 23 = 13 v pin 23 i 23 100 a trigger threshold (internal pull down resistor) pins 16, 17, 28 v ttx x=16,17,18 0.33 v batt v input current v batt = 13 v i 100 a test test voltage for delay time override i = 20 ma pin 15 v 15 23 v dimensions in mm package: so 28 95 9932
telefunken semiconductors U2481B/ u2482b preliminary information rev. a1: 21.08.1995 11 (11) ozone depleting substances policy statement it is the policy of temic telefunken microelectronic gmbh to 1. meet all present and future national and international statutory requirements. 2. regularly and continuously improve the performance of our products, processes, distribution and operating systems with respect to their impact on the health and safety of our employees and the public, as well as their impact on the environment. it is particular concern to control or eliminate releases of those substances into the atmosphere which are known as ozone depleting substances ( odss). the montreal protocol ( 1987) and its london amendments ( 1990) intend to severely restrict the use of odss and forbid their use within the next ten years. various national and international initiatives are pressing for an earlier ban on these substances. temic telefunken microelectronic gmbh semiconductor division has been able to use its policy of continuous improvements to eliminate the use of odss listed in the following documents. 1. annex a, b and list of transitional substances of the montreal protocol and the london amendments respectively 2 . class i and ii ozone depleting substances in the clean air act amendments of 1990 by the environmental protection agency ( epa ) in the usa 3. council decision 88/540/eec and 91/690/eec annex a, b and c ( transitional substances ) respectively. temic can certify that our semiconductors are not manufactured with ozone depleting substances and do not contain such substances. we reserve the right to make changes to improve technical design and may do so without further notice . parameters can vary in different applications. all operating parameters must be validated for each customer application by the customer. should the buyer use temic products for any unintended or unauthorized application, the buyer shall indemnify temic against all claims, costs, damages, and expenses, arising out of, directly or indirectly, any claim of personal damage, injury or death associated with such unintended or unauthorized use. temic telefunken microelectronic gmbh, p.o.b. 3535, d-74025 heilbronn, germany telephone: 49 ( 0 ) 7131 67 2831, fax number: 49 ( 0 ) 7131 67 2423

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