U6081B telefunken semiconductors rev. a1, 03-dec-97 1 (8) pwm power control with low duty-cycle switch off description the U6081B is a pwm ic in bipolar technology for the control of an n-channel power mosfet used as a high- side switch. the ic is ideal for the use in the brightness control (dimming) of lamps e.g., in dashboard applications. features pulse-width modulation up to 2 khz clock frequency protection against short circuit, load-dump overvol- tage and reverse v s duty cycle 0 to 100% output stage for power mosfet interference and damage protection according to vde 0839 and iso/tr 7637/1. ground-wire breakage protection charge-pump noise suppressed ordering information extended type number package remarks U6081B dip8 block diagram current monitoring + short circuit detection output charge pump rc oscillator duty cycle range 0/13 to 100 % control input voltage monitoring 5 1 4 3 v s c 5 pwm logic 6 7 8 47 k 47 nf r sh 2 r 3 150 95 9752 v batt c 3 c 2 c 1 ground figure 1. block diagram with external circuit
U6081B telefunken semiconductors rev. a1, 03-dec-97 2 (8) pin description 1 2 3 4 5 6 7 8 95 9944 v s gnd v i osc output sense 2 v s delay pin symbol function 1 v s supply voltage v s 2 gnd ic ground 3 v i control input (duty cycle) 4 osc oscillator 5 delay short circuit protection delay 6 sense current sensing 7 2 v s voltage doubler 8 output output functional description pin 1, supply voltage, v s or v batt overvoltage detection stage 1: if v batt > 20 v, the external transistor will be switched off and switched on again at v batt < 18.5 v (hysteresis). stage 2: if v batt > 28 v, the external transistor is switched on again (load-dump protection). at the same time the voltage limitation of the ic is reduced from v s 26 v to v s 0 v. this leads to a hysteresis characteristic so that the load-dump detection is switched off again only at v batt < 23 v. in this case the shortcircuit protection is not in operation. undervoltage detection in the event of voltages of approximately v batt < 5.0 v, the external fet is switched off and the latch for short-circuit detection is reset. a hysteresis ensures that the fet is switched on again at approximately v batt 5.4 v. pin 2, gnd ground-wire breakage to protect the fet in the case of ground-wire breakage, a 820-k resistor between gate and source is recommended to provide proper switch-off conditions. pin 3, control input the pulse width is controlled by means of an external potentiometer (47 k ). the characteristic (angle of rotation/duty cycle) is linear. the duty cycle can be varied from 0 to 100%. to avoid inadmissibly high filament cold currents, the dimmer is switched off at duty cycles of approximately < 10% or is switched on only at duty cycles of approximately > 13% (hysteresis). it is possible to further restrict the duty cycle with the resistors r 1 and r 2 (see figure 2). pin 3 is protected against short-circuit to v batt and ground gnd (v batt 16.5 v). output slope control the rise and fall time (t r , t f ) of the lamp voltage can be limited to reduce radio interference. this is done with an integrator which controls a power mosfet as source follower. the slope time is controlled by an external capacitor c4 and the oscillator current (see figure 2). calculation: t f t r v batt c 4 i osc with v batt = 12 v, c 4 = 470 pf and i osc = 40 a, we thus obtain a controlled slope of t f t r 12 v 470 pf 40 a 141 s a 100- resistor in series to c4 is recomended to damp device oscillations (see figure 2). pin 4, oscillator the oscillator determines the frequency of the output voltage. this is defined by an external capacitor, c 2 . it is charged with a constant current, i, until the upper switching threshold is reached. a second current source is then activated which taps a double current, 2 i, from the charging current. the capacitor, c 2 , is thus discharged by the current, i, until the lower switching threshold is reached. the second source is then switched off again and the procedure starts again. example for oscillator frequency calculation: v t100 v s 1 ( v batt i s r 3 ) 1 v t 100 v s 2 ( v batt i s r 3 ) 2 v tl v s 3 ( v batt i s r 3 ) 3 where
U6081B telefunken semiconductors rev. a1, 03-dec-97 3 (8) v t1 00 hi g h switchin g threshold (100% dut y c y cle) v t 100 high switching threshold ( 100% duty cycle) v tl low switching threshold 1 , 2 and 3 are fixed values. the above mentioned threshold voltages are calculated for the following values given in the data sheet. v batt = 12 v, i s = 4 ma, r 3 = 150 , 1 = 0.7, 2 = 0.67 and 3 = 0.28. v t100 ( 12 v 4ma 150 ) 0.7 8v v t 100 11.4 v 0.67 7.6 v v tl 11.4 v 0.28 3.2 v for a duty cycle of 100%, the oscillator frequency, f, is as follows: f i osc 2 ( v t100 v tl ) c 2 ,whereasc 2 22 nf and i osc 40 a therefore: f 40 a 2 ( 8v 3.2 v ) 22 nf 189 hz for a duty cycle of less than 100%, the oscillator frequency, f, is as follows: f i osc 2 ( v t 100 v tl ) c 2 4 v batt c 4 whereas c 4 = 470 pf f 40 a 2 ( 7.6 v 3.2 v ) 22 nf 4 12 v 470 p f 185 hz a selection of different values of c 2 and c 4 provides a range of various oscillator frequencies from 10 to 2000 hz. pins 5 and 6, short-circuit protection and current sensing 1. short-circuit detection and time delay, t d the lamp current is monitored by means of an external shunt resistor. if the lamp current exceeds the threshold for the short-circuit detection circuit (v t2 90 mv), the duty cycle is switched over to 100% and the capacitor c 5 is charged by a current source of 20 a (i ch i dis ). the external fet is switched off after the cut-off threshold (v t5 ) is reached. renewed switching on the fet is possible only after a power-on reset. the current source, i dis, ensures that the capacitor c 5 is not charged by parasitic currents. the capacitor c 5 is discharged by i dis to typ. 0.7 v. time delay, t d , is as follows: t d c 5 ( v t5 0.7 v ) ( i ch i dis ) with c 5 = 330 nf and v t5 = 9.8 v, (i ch i dis ) = 20 a, we have t d 330 nf ( 9.8 v 0.7 v ) 20 a 150 ms. 2. current limitation the lamp current is limited by a control amplifier to pro- tect the external power transistor. the voltage drop across an external shunt resistor acts as the measured variable. current limitation takes place for a voltage drop of v t1 100 mv. owing to the difference v t1 v t2 10 mv it is ensured that current limitation occurs only when the short circuit detection circuit has responded. after a power-on reset, the output is inactive for an half oscillator cycle. during this time, the supply voltage capacitor can be charged so that the current limitation is guaranteed in the event of a short circuit when the ic is switched on for the first time. pins 7 and 8, charge pump and output pin 8 (output) is suitable for controlling a power mosfet. during the active integration phase, the supply current of the operational amplifier is mainly supplied by the capacitor c 3 (bootstrapping). additionally, a trickle charge is generated by an integrated oscillator (f 7 400 khz) and a voltage doubler circuit. this permits a gate voltage supply at a duty cycle of 100%.
U6081B telefunken semiconductors rev. a1, 03-dec-97 4 (8) absolute maximum ratings parameters symbol value unit junction temperature t j 150 c ambient temperature range t amb 40 to +110 c storage temperature range t stg 55 to +125 c thermal resistance parameters symbol maximum unit junction ambient r thja 120 k/w electrical characteristics t amb = 40 to +110 c, v batt = 9 to 16.5 v, (basic function is guaranteed between 6.0 v to 9.0 v) reference point is ground, unless otherwise specified (see figure 1). all other values refer to pin gnd (pin 2). parameters test conditions / pins symbol min typ max unit current consumption pin 1 i s 6.8 ma supply voltage overvoltage detection, stage 1 v batt 25 v stabilized voltage i s = 10 ma pin 1 v z 24.5 27.0 v battery undervoltage detection on off v batt 4.4 4.8 5.0 5.4 5.6 6.0 v battery overvoltage detection pin 2 stage 1: on off v batt 18.3 16.7 20.0 18.5 21.7 20.3 v stage 2: on off v batt 25.5 19.5 28.5 23.0 32.5 26.5 v stabilized voltage i s = 30 ma pin 1 v z 18.5 20.0 21.5 v short-circuit protection pin 6 short-circuit current limitation v t1 = v s v 6 v t1 85 100 120 mv short-circuit detection v t2 = v s v 6 v t2 75 90 105 mv v t1 v t2 3 10 30 mv delay timer short-circuit detection, v batt = 12 v pin 5 switched off threshold v t5 = v s v 5 v t5 9.5 9.8 10.1 v charge current i ch 23 a discharge current i dis 3 a capacitance current i 5 = i ch i dis i 5 13 20 27 ma voltage doubler pin 7 voltage duty cycle 100% v 7 2 v s oscillator frequency f 7 280 400 520 khz internal voltage limitation i 7 = 5 ma v 7 26 27.5 30.0 v g (whichever is lower) v 7 v s+14 v s+15 v s+16 v
U6081B telefunken semiconductors rev. a1, 03-dec-97 5 (8) parameters test conditions / pins symbol min typ max unit switch-off at small duty cycles v batt = 12 v pin 3 output disabled v 3 /v s 0.3 0.32 0.34 output active v 3 /v s 0.32 0.34 0.36 hysteresis switch-on v 3 /v s 0.004 0.032 gate output pin 8 voltage low level v 8 0.35 0.70 0.95 v g v batt = 16.5 v, t amb = 110 c, r 3 = 150 1.5 *) high level, duty cycle 100% v 8 v 7 current v 8 = low level i 8 1.0 ma v 8 = high level, i 7 > | i 8 | 1.0 oscillator frequency pin4 f 10 2000 hz threshold cycle upper v 8 high, 1 v t100 v s 1 0.68 0.7 0.72 upper v 8 low, 2 v t 100 v s 2 0.65 0.67 0.69 lower 3 v tl v s 3 0.26 0.28 0.3 oscillator current v batt = 12 v i osc 34 45 54 a frequency tolerance c 4 open, c 2 = 470 nf, duty cycle = 50% f 6.0 9.9 13.5 hz *) reference point is battery ground
U6081B telefunken semiconductors rev. a1, 03-dec-97 6 (8) package information 13021 9.8 9.5 package dip8 dimensions in mm 1.64 1.44 4.8 max 0.5 min 3.3 0.58 0.48 7.62 2.54 6.4 max 0.36 max 9.8 8.2 7.77 7.47 85 14 technical drawings according to din specifications
U6081B telefunken semiconductors rev. a1, 03-dec-97 7 (8) application + + v s + reset v s 5 v s i ch 1 reset switch on delay 2 i v s i oscillator 3 4 30 k 100 v s overvoltage monitoring stage 1 low voltage monitoring v s v s reset 2 overvoltage monitoring stage 2 voltage doubler v s + 90 mv 10 mv v s current limiting 6 c 4 c 3 47 nf 820 k r sh v batt c 5 8 7 r 3 150 ground r 1 r 2 c 2 c 1 47 k 47 f load r l i dis 95 9759 duty factor = 10% + + + + 470 pf 330 nf 22 nf figure 2.
U6081B telefunken semiconductors rev. a1, 03-dec-97 8 (8) 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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