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rev. 4808a?auto?06/04 features two identical interface channels pre-regulated smoothed voltage and a supply current up to 50 ma for the sensors data from the sensors by current modulation with a transmission rate of 60 kbaud (transmission bandwidth 500 khz) ttl-compatible input activates the sensor data output can be directly connected to a microcontroller input operation supply voltage range 5.7 v v s 40 v esd protection according to mil-std-883c test method 3015.7 high-level emi protection benefits simple wiring thanks to one common line for supply of the sensor and data transmission from the sensor to the u6268b current modulation provides high noise immunity for data transfer description the u6268b is an interface ic for remote automotive sensors. it links the crash sen- sors in the driver and passenger door with the main airbag unit in the dashboard. two identical channels supply the external s ensors and receive digital information from them via one active wire each. the interface supplies the external sensors with a pre- regulated smoothed voltage, the external units transmit the digital information back to the interface by current modulation. as the device is designed for safety-critical applications, the highest data transmission security is mandatory. with high immunity against cross coupling between the two channels, the u6268b is tailored for the harsh automotive environment. figure 1. block diagram short circuit detection temperature monitor smoothed voltage regulator i/v converter smoothed voltage regulator i/v converter voltage comparator channel 1 data enable enable voltage comparator channel 2 data crash sensor channel 1 channel 2 channel 1 power supply data trans- mission crash sensor channel 2 power supply data trans- mission microcontroller side-airbag sensor dual interface u6268b
2 u6268b 4808a?auto?06/04 pin configuration figure 2. pinning so16 vs out1 out2 sc return2 gnd gnd return1 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 cll1 ocm1 ocm2 cll2 enable2 gnd gnd enable1 pin description pin symbol function 1 gnd ground and reference pin 2 return1 return line of the external unit, internally connected to gnd via a line-protection transistor 3 out1 voltage-stabilized supply output and current-modulation input 4 vs supply voltage of the ic 5 out2 voltage-stabilized supply output and current-modulation input 6 sc smooth time constant for slow voltage change at both out pins 7 return2 return line of the external unit, internally connected to gnd via a line-protection transistor 8, 9 gnd ground and reference pin 10 enable2 controls out1 voltage enable1 high = out1 active, enable1 low or open = out1 switched off 11 cll2 current logic level output (low at high out2 current, monitoring via ocm2) 12 ocm2 analog current output, representing 1/10 current of out2 13 ocm1 analog current output, representing 1/10 current of out1 14 cll1 current logic level output (low at high out1 current, monitoring via ocm1) 15 enable1 controls out2 voltage enable2 high = out2 active, enable1 low or open = out2 switched off 16 gnd ground and reference pin
3 u6268b 4808a?auto?06/04 figure 3. functional block diagram voltage regulator i sc-dis + - i sc-ch current mirror ratio i ocmx /i outx i out over current limi- tation v out on off temperature protection high t > 165c low t < 145c if enable x = 9 v then temp = high high = enable outx test mode temp reset set latch + - + - v ocm-det v ocm-lim temp + - i ocm-sink v cll-x - + i out-sink 4.2 v i ret-low 3 ? + - ocmx gnd sc enablex cllx outx - + 5 v/ms at v s rising 10 v/ms at v s falling slew rate v out v s returnx v ret_x current limitation v sc v s v sc v s
4 u6268b 4808a?auto?06/04 functional description v s the ic and the external units are powered via the v s pin 4. this pin is connected to the battery via a reverse battery protection diode. an electrolythic capacitor of 22 f smoothes the voltage and absorbes positive and negative transients. out1, out2 outx provides a smoothed, very slowly changing supply voltage for the external units and monitors the output current. during normal operating conditions, the outx voltage is typically 3 v below v s , and changes very slowly with a varying battery voltage in order to suppress disturbances in the data transmission. at low v s (5.7 to 8.5 v), the outx voltage is typically 0.5 v below v s . this voltage difference is reduced in to ensure suffi- cient supply voltage for the external unit between outx and returnx. the output current capability is 50 ma. the internal pull-down current at outx is typically 3 ma. figure 4. output voltage with tolerances versus supply voltage the data transmission from the external unit to the interface ic is carried out on the same line by varying the current level. the quiescent current consumption of the exter- nal unit is about 5 to 15 ma. this current level is interpreted as logic high level at the cll pin. the external unit can switch on an additional current of 30 ma, interpreted by the interface as logic low. the slope time of the current pulse is approximately 1 s which is suitable for a transmission rate up to 60 kbaud. the necessary transmission bandwidth of greater than 500 khz between outx and ocmx is guaranteed (see ?appli- cation circuit? on page 12). to achieve good current transmission behavior, the dynamic resistance of outx may not exceed 12 ? within the bandwidth range (total of 15 ? for outx and return). the outx voltage can be switched off by enablex = low to reset the external unit and to reduce power dissipation during fault conditions. the out pins are protected against overtemperature and short circuits. a reverse polar- ity diode at pin v s (pin 4) ensures that no current is fed back to the v batt system in the case of a short between outx and v batt . a minimum capacity of 33 nf is required at the pins outx. 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 40 v s (v) v out (v) voutmax voutmin 32.6 28.6 12.0 11.3 8.5 5.7 22.4 21.4 9.4 8.2 7.7 5.4 4.9
5 u6268b 4808a?auto?06/04 enable1, enable2 enablex is a microcontroller-compatible input which switches the related output on or off. a low or open circuit applied to enablex switches off the related outx and returnx (high impedance). a sink current at pin outx discharges the capacitive load. a high applied to enablex switches on the related outx and returnx to supply the external unit. ocm1, ocm2 the output current of outx is monitored with a transmission factor of 0.1 to the ocmx. with a resistor from ocm to gnd, the current is converted to a voltage. the electrical characteristics are specified by r ocm = 750 ? . the cll-current threshold, the out-cur- rent limitation and the out-current detection can be changed by varying r ocm in a range of 500 ? to 1 k ? . current monitoring enables the device to detect overcurrent conditions at outx (short-circuit to gnd or returnx) and low current conditions at outx (short-circuit to v batt or open load). the internal pull-down current at outx creates no ocmx-current. during enable, the minimum voltage at ocmx is the saturation voltage of an internal npn-transistor with typically 0.1 v. the maximum voltage at ocm is limited by an internal clamping diode to 5.3 v. cll1, cll2 the current at pin outx is evaluated logically and ready to use for a microcontroller input. with this stage, the logic data transmission from the external unit to the interface is completed. cllx is the output stage of a comparator with an internal threshold and with the ocmx input. a ocmx voltage higher than 2.4 v creates a logic low at cllx, and a ocmx volt- age lower than 1.43 v creates a logic high at cllx. the comparator has an internal hysteresis of typically 0.4 v. with the pull-down resistor r ocmx =750 ? at ocmx, the correct outx-current threshold related to the logical output cllx is ensured. the cllx is low if the outx-current is higher than 27.3 ma, and the cllx is ?high?, if the outx-current is lower than 19.1 ma. the comparator has an internal hysteresis of typically 5 ma. the tolerance of the rocm resistor is assumed to be 0%. the cll pin is an open-collector output and needs a pull-up resistor of typically 2 k ? to the 5-v supply. for esd protection, a 7-v zener diode is implemented. return 1, return 2 the returnx pin provides a low-ohmic connection to gnd via a switched open-collec- tor npn-transistor. if enablex is high, returnx is switched on with a saturation voltage of less than 0.5 v at i returnx 50 ma. if enablex is low or open, returnx is a current sink with 2 ma. returnx is current-limited at typically 150 ma. sc the smooth capacitor is designed to realize the long-time constant for the slow voltage change at outx for both interface channels. the capacity is typically 22 nf. at the rising edge of v batt , the maximum slew rate is v outx = 5 v/ms, and at the falling edge of v batt , the maximum slew rate is v outx = 10 v/ms.
6 u6268b 4808a?auto?06/04 gnd pins a gnd bond from the chip to pin 1 and pin 8 provides high ground breakage security and the lowest voltage drop and ground shift between the ic and circuit ground. the four gnd pins and the die pad are directly connected to the copper leadframe, resulting in a very low thermal resistance, r thjc . to also achieve a low ambient thermal resis- tance (r thja ) it is recommended metal parts of the housing be connected in a proper way with the gnd pins. power dissipation worst case calculation of the supply current i s : i s = 1,278 (i out1 + i out2 ) + 18 ma worst case calculation of the ic's power dissipation p v : p v = (v s i s ) - [(v s - v diff - v ret-sat ) (i out1 + i out2 ) + r ocm ((i out1 2 + i out2 2 )/81)] v s = supply voltage (5.7 to 25 v) v diff = v s to v outx voltage difference v diff = 3.6 v at 12 v v s 25 v v diff = 0.8 v at 5.7 v v s 8.5 v v ret-sat = 0.5 v saturation voltage return i outx = output current at pin outx = 0 to 60 ma r ocm = resistor at pin ocmx an integrated overtemperature protection generates a switch-off signal at a chip temper- ature of typically t j = 160c and a switch-on signal at typically t j = 150c. if overtemperature is detected, only the corresponding channel will be disabled. the other channel stays enabled. the returnx is switched off if the voltage at returnx exceeds 2 v (short-circuit comparator threshold) and overtemperature is detected. the outx is switched off if the voltage at ocmx is higher than 4.6 v (overcurrent detec- tion level) and overtemperature is detected. the ocm voltage monitors the output current at outx via the current ratio of 0.1. the overcurrent-detection level of outx can be varied by changing the ocmx resistor. if outx is switched off by overtemperature and overcurrent detection, the cllx output remains a logic low (overcurrent). as the ic is only overtemperature-prot ected against short-ci rcuit conditions at returnx or outx, it has to be checked in each application that the chip temperature does not exceed t jmax = 150c in normal operation. test hint the overtemperature signal can be activated by connecting enable1 or enable2 to 9v/10 ma.
7 u6268b 4808a?auto?06/04 note: 1. a good ambient thermal resistance junction (r thja = 65 k/w) can be achieved by using a big pad size for ground connection near a metal component (see section ?gnd pins? on page 6) absolute maximum ratings stresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. this is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability . parameters symbol min. max. unit supply voltage v s -0.6 40 v voltage at pins cll1, cll2, enable1, enable2 -0.3 6 v voltage at sc v sc -0.3 30 v voltage at ocm1, ocm2 v ocmx -0.3 6.8 v voltage at return1, return2 v returnx -1 27 v voltage at out1, out2 v outx -1 40 v current at supply (both channels outx and returnx shorted) i s 240 ma current at logical pins: cll1, cll2 enable1, enable2 i cclx i enablex 3 0.1 ma ma current at sc (sc related to gnd or v batt )i sc -110 220 a current at pins to external unit out1, out2, return1, return2 internally limited esd classification human body model (100 pf, 1.5 k ? ) machine model (200 pf, 0.0 ? ) all pins 2000 200 v v ambient temperature range t amb -40 95 c junction temperature range t j -40 150 c storage temperature range t stg -55 125 c thermal resistance (1) parameters symbol value unit junction case r thjc 36 k/w
8 u6268b 4808a?auto?06/04 electrical characteristics t amb = -40c to 95c and t j = -40c to 150c, operation supply-voltage range v s = 5.7 to 18 v continuously, v s 25 v for maximum 25 min, v s 40 v for up to 500 ms. the current values are based on r = 750 ? , 0%-resistor at ocm1/ocm2 pins. parameters test conditions symbol min. typ. max. unit supply current t j 125c outputs disabled, v s 18 v i s 8ma outputs disabled, v s 40 v i s 14 ma one output enabled, v s 18 v i s 13 ma both outputs enabled, v s 18 v i s 18 ma output load 2 15 ma, v s 18 v i s 56 ma output load 2 28 ma, v s 18 v i s 90 ma output load 2 50 ma, v s 18 v i s 146 ma output load 2 60 ma, v s 18 v (t j > 125c) i s 171 ma both channels outx and returnx shorted, v s 18 v i s 200 ma function sc voltage at sc v s = 5.7 v v sc 5.1 5.3 v voltage at sc v s = 12.5 v v sc 99.4v maximal voltage at sc v s = 40 v v scmax 30 v sc-discharge current voltage sc = v sc - 3 v 5.7 v v s 40 v i sc_dis 33 82 a sc-charge current voltage sc = v sc - 3 v 5.7 v v s 40 v i sc_ch -58 -20 a function out1 and out2 (see figure 4 on page 4) voltage difference, v s to v outx i outx = 5 to 50 ma 5.7 v v s 8.5 v 12 v v s 25 v v diff_low v diff_high 0.3 2.6 0.8 3.6 v v output voltage outx 8.5 v v s 11.3 v v out_med 7.7 v maximal voltage at outx v s = 40 v v out_max 25 30 v current mirror ratio, i ocmx /i outx v s 40 v, i outx = 5 to 15 ma v s 25 v, i outx = 15 to 50 ma v s 40 v, i outx = 15 to 50 ma i out_ratio 0.09 0.10 0.097 0.12 0.11 0.11 linearity of mirror ratio i ocmx /i outx ratio_lin -5 5 % dynamic resistance outx v s 40 v i out = 15 to 50 ma r out 212 ? dynamic resistance outx + returnx v s 40 v i out = 15 to 50 ma r dyn 415 ? outx current limitation (outx short to gnd) v s 18 v v s 40 v i out_lim -80 -105 -60 -60 ma ma overcurrent detection level t j < 125c i out_det -70 -51 ma t j 125c always valid: current limitation is higher than overcurrent detection i out_det -60 -51 ma maximum outx current (outx short to gnd) v s = 14 v, ocmx shorted to gnd i out_max -140 -85 ma
9 u6268b 4808a?auto?06/04 leakage current at disabled outx outx short to gnd, v s 25 v outx short to gnd, v s 38.5 v i out_leak -0.02 -12 ma ma leakage voltage at disabled outx outx open, v s 38.5 v v out_leak 4.3 v internal pull-down current v s 18 v v s 40 v i out_sink 1.8 2.5 4 4.5 ma ma supply rejection ratio v sc = 7.6 v v rej_mv 80 mv supply rejection ratio variation of v s = 8.4 v to 40 v in 10 ms v rej_db 51.9 db minimum capacity at outx for phase margin c out_min 33 nf delay time with c out = 47 nf switching on enable = 1 to 90% v out reached switching off enable = 0 to 10% v out reached enable_on enable_off 3 30 30 100 s s function ocm1, ocm2 voltage threshold cll-comparator cllx low-level voltage threshold cllx high-level voltage threshold voltage hysteresis v cll_l v cll_h v cll_hys 1.75 1.43 0.26 2.4 1.9 0.6 v v v minimum voltage at ocmx i out = 0 to 5 ma v ocm_min 0.5 v current-limitation level v s 40 v, outx short to gnd v ocm_lim 4.3 5.3 v overcurrent-detection level v s 40 v v ocm_det 4.2 4.9 v current limitation minus overcurrent detection v ocm_lim - v ocm_over ? _lim_ocm 0.15 0.5 v internal pull-down current i ocm_sink 0.1 0.45 ma function return1, return2 enable high saturation voltage i return = 50 ma v ret_sat 0.5 v dynamic resistance di 10 ma r ret 28 ? current limitation returnx is always higher than current limitation outx enable high, v returnx = 2 v enable high, v returnx 18 v enable low, v returnx 18 v i ret_lim i ret_lim i ret_low 60 70 0.8 150 200 2 ma ma ma overcurrent-detection level threshold comparator, switch-off return threshold comparator, switch-on return hysteresis v ret_low v ret_high v ret_hys 1.4 1.1 0.2 2 1.5 0.7 v v v delay time c return = 47 nf switching on i return at 50 ma switching off i return at 1 ma t dret_on t dret_off 3 30 30 90 s s function cll1, cll2 (cllx with 2 k ? to 5 v) i out threshold cll comparator r ocm = 750 ? cll low-level threshold cll high-level threshold hysteresis i cll_l i cll_h i cll_hys 23.3 19.1 3.5 27.3 22.3 8.2 ma ma ma cll saturation voltage i cll 2.5 ma v cll_sat 0.4 v electrical characteristics (continued) t amb = -40c to 95c and t j = -40c to 150c, operation supply-voltage range v s = 5.7 to 18 v continuously, v s 25 v for maximum 25 min, v s 40 v for up to 500 ms. the current values are based on r = 750 ? , 0%-resistor at ocm1/ocm2 pins. parameters test conditions symbol min. typ. max. unit
10 u6268b 4808a?auto?06/04 cll leakage current v cll 6.5 v i cll_leak 1a response time to current change i out to cll rise i out to cll fall maximum difference between rise and fall time t cll_rise t cll_fall t ? -rise-fall 0.1 0.1 2 2 1 s s s cll output switching speed rise fall t cll_rise t cll-fall 1 1 s s current transmission rate 60 khz current transmission 3 db bandwidth 500 khz function enable1, enable2 enable high-level threshold v enable_on 26.5v enable low-level threshold v enable_off -0.3 0.8 v enable input pull-down current (to ensure output disabled during power-off and reset of microcontroller) i enable 10 100 a power dissipation power dissipation 1 t j 125c v s = 18 v, i out1 = 28 ma, i out2 at overcurrent detection level p dis1 1w or i out2 = 28 ma, i out1 at overcurrent detection level power dissipation 2 t j 125c v s = 18 v, i out1 = i out2 = 28 ma p dis2 0.75 w selective overtemperature protection logic and connected with overcurrent detection (returnx, outx) switch off switch on hysteresis te m p _ o f f te m p _ o n te m p _ hy s 155 145 5 165 155 20 c c c time delay until overtemperature shut-down v s = 25 v, t amb = 125c out1 = out2 = gnd t del 100 ms electrical characteristics (continued) t amb = -40c to 95c and t j = -40c to 150c, operation supply-voltage range v s = 5.7 to 18 v continuously, v s 25 v for maximum 25 min, v s 40 v for up to 500 ms. the current values are based on r = 750 ? , 0%-resistor at ocm1/ocm2 pins. parameters test conditions symbol min. typ. max. unit
11 u6268b 4808a?auto?06/04 timing diagrams figure 5. variation of power supply figure 6. overcurrent protection 14.0 v 12.0 v v s 10.7 v 8.7 v v sc 10.7 v 8.7 v 0.4 ms 0.2 ms t v outx 5.0 v 75 ma 15 ma overcurrent overtemperature shut down 5.0 v v cllx 100 ms 150 ms 75 ms pause/pulse for example (pulse/pause time depends on power disipation and r thja ) t overcurrent overcurrent i outx v enablex
12 u6268b 4808a?auto?06/04 figure 7. data transmission figure 8. application circuit 200 mv 150 s 13 v discharge of c out = 47 nf with internal current charge time c out = 47 nf current modulation from sensor 40 ma 10 ma 4.7 v 3.0 v 0.75 v 5.0 v 0 v v cllx t 60 ma overcurrent overcurrent 50 s v ocmx i outx v outx v enablex 30 s 5 v 47 nf 47 nf out1 return1 3 2 enable1 ocm1 enable2 cll2 ocm2 u6268b interface1 interface2 22 nf gnd sc +v batt i/o i/o i/o sensor 1 sensor 2 v s microcontroller 22 mf 100 nf cll1 i/o 1, 8, 9, 16 6 14 15 13 11 10 12 4 5 v 47 nf 47 nf out2 return2 5 7 750 750 v cc = 5 v v cc = 5 v
13 u6268b 4808a?auto?06/04 package information ordering information extended type number package remarks U6268B-FP so16 ? technical drawings according to din specifications package so16 dimensions in mm 10.0 9.85 8.89 0.4 1.27 1.4 0.25 0.10 5.2 4.8 3.7 3.8 6.15 5.85 0.2 16 9 18
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