U6268B Side-Airbag Sensor Dual Interface Description The U6268B is an interface IC for remote automotive sensors. It links the crash sensors in the driver- and passenger door with the main airbag unit in the dashboard. Two identical channels supply the external sensors 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 for safety critical applications, 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. Features Two identical interface channels TTL-compatible input activate the sensor Provides a pre-regulated smoothed voltage and a supply current up to 50 mA for the sensors Data output can be directly connected to a microcontroller input Receives data from the sensors by current modulation with a transmission rate of 60 kBaud (transmission bandwidth 500 kHz) Operation supply voltage range 5.7 V VS 40 V Current modulation provides high noise immunity for data transfer ESD protection according to MIL-STD-883C test method 3015.7 High-level EMI protection Benefits Voltage supply and data transmission with one active wire over long distances Block Diagram Data Channel 1 Voltage comparator Smoothed voltage regulator Enable Channel 1 µC Channel 2 Enable Channel 2 Data I/V converter Temperature monitor Data trans– mission Crash sensor Short circuit detection Smoothed voltage regulator Voltage comparator Channel 1 power supply I/V converter Channel 2 power supply Data trans– mission Crash sensor 13839 Figure 1. Block diagram Ordering Information Extended Type Number Package U6268B–FP SO16 Rev. A3, 11-Apr-01 Remarks 1 (13) U6268B Pin Description GND 16 GND 1 RETURN1 2 Symbol 1 GND 2 15 ENABLE1 OUT1 3 VS Pin 13 OCM1 OUT2 5 12 OCM2 SC 6 11 CLL2 3 OUT1 4 VS 5 OUT2 Voltage stabilized supply output and current modulation input 6 SC Smooth time constant for slow voltage change at both OUT pins 7 10 ENABLE2 RETURN2 7 8, 9 GND 9 8 GND 10 13321 Figure 2. Pinning Voltage-stabilized supply output and current-modulation input Supply voltage of the IC RETURN2 Return line of the external unit, internally connected to GND via a line-protection transistor GND Ground and reference pin ENABLE2 Controls OUT1 voltage, ENABLE1 High means OUT1 active, ENABLE1 Low or open means 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 16 2 (13) Ground and reference pin RETURN1 Return line of the external unit, internally connected to GND via a line-protection transistor 14 CLL1 4 Function ENABLE1 Controls OUT2 voltage, ENABLE2 High means OUT2 active, ENABLE1 Low or open means OUT2 switched off GND Ground and reference pin Rev. A3, 11-Apr-01 U6268B VS Slew rate Vout 5 V/ms @ VS rising 10 V/ms @ VS falling Voltage Regulator Current mirror ratio Iocmx / Ioutx VSC VS VS Isc–ch VSC – + SC Iout + – Over current limi– tation Vout OUTx ON OFF Isc–dis Iout–sink Temperature protection high T > 165°C low T < 145°C ENABLEx Temp Latch Reset Set – + High = ENABLE OUTx 4.2 V Test mode If ENABLE x = 9 V then Temp = high CLLx – + Vocm–det Temp Vocm–lim OCMx + – Vcll–x Current limitation Iocm–sink + – Vret_x – + RETURNx 3Ω Iret–low GND 13948 Figure 3. Functional block diagram Rev. A3, 11-Apr-01 3 (13) U6268B Functional Description voltage for the external units and monitors the output current. During normal operating conditions, the OUTx voltage is typ. 3 V below VS, and changes very slowly with a varying battery voltage in order to suppress disturbances in the data transmission. At low VS (5.7 to 8.5 V), the OUTx voltage is typ. 0.5 V below VS. This voltage difference is reduced in order to ensure sufficient 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. VS The IC and the external units are powered via the VS 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 35 Vout max 30 Vout min Vout ( V ) 25 22.4 21.4 20 15 9.4 10 8.2 7.7 5.4 5 4.9 0 0 13322 5 5.7 8.5 10 15 11.3 12.0 20 25 30 28.6 35 40 32.6 VS ( V ) Figure 4. Output voltage with tolerances vs. 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 external unit is about 5 to 15 mA. This current level is interpreted as logic high level at CLL-pin. The external unit can switch on an additional current of 30 mA, interpreted by the interface as logic low. The current changes within approximately 1 s, sufficient for a transmission rate of about 60 kBaud, requiring a transmission bandwidth of about 500 kHz for the currentmonitoring subcircuit and the OCM output. For a good current transmission behaviour, the dynamic resistance of 4 (13) OUTx may not exceed 12 inside 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 overtemperature- and short-circuit protected. A reverse polarity diode at Pin VS (Pin 4) ensures that no current is fed back to the VBatt-system in the case of a short between OUTx and VBatt. A minimum capacity of 33 nF is required at the pins OUTx. Rev. A3, 11-Apr-01 U6268B ENABLE1, ENABLE2 ENABLEx is a microcontroller-compatible input which switches the related output on or off. 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. High applied to ENABLEx switches on the related OUTx and RETURNx to supply the external unit. 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-collector NPN-transistor. If ENABLEx is high, RETURNx is switched on with a saturation voltage less than 0.5 V at IRETURNx 50 mA. If ENABLEx is low or open, RETURNx is a current sink with 2 mA. RETURNx is current-limited at typically 150 mA. OCM1, OCM2 SC 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 ROCM = 750 . The CLL-current threshold, the OUT-current limitation and the OUT-current detection can be changed by varying ROCM in a range from 500 to 1 k. 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 typ. 22 nF. At the rising edge of VBatt, the maximum slew rate is VOUTx = 5 V/ms, and at the falling edge of VBatt, the maximum slew rate is VOUTx = 10 V/ms. The current monitoring enables to detect overcurrent conditions at OUTx (short circuit to GND or RETURNx) and to detect low current conditions at OUTx (short circuit to VBatt or open load). The internal pull-down current at the 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 GND-Pins By means of a GND bond from the chip to Pin 1 and Pin 8, high ground breakage security is achieved and lowest voltage drop and ground shift between IC- and circuit ground is provided. The four GND pins and the die pad are directly connected to the copper leadframe, resulting in a very low thermal resistance, RthJC. In order to achieve a good thermal resistance, RthJA, a good copper connection from the four GND pins to the metal parts of the modul housing is also recommended. Power Dissipation Worst case calculation of the supply current IS: 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-voltage lower than 1.43 V creates a logic high at CLLx. The comparator has an internal hysteresis with typically 0.4 V. With the pull-down resistor ROCMx = 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%. Rev. A3, 11-Apr-01 IS = 1,278 ( IOUT1 + IOUT2 ) + 18 mA Worst case calculation of the IC’s power dissipation PV: PV = (VSIS) – [(VS – Vdiff – Vret-sat)(IOUT1 + IOUT2) +ROCM((IOUT12 + IOUT22) / 81)] VS = 5.7 to 25 V supply voltage Vdiff = VS to VOUTx voltage difference Vdiff = 3.6 V at 12 V VS 25 V Vdiff = 0.8 V at 5.7 V VS 8.5 V Vret-sat = 0.5 V saturation voltage return IOUTx = output current at Pin OUTx = 0 to 60 mA ROCM = resistor at Pin OCMx An overtemperature protection is integrated which generates a switch-off signal at a chip temperature of typically Tj = 160°C and a switch-on signal at typically Tj = 150°C. 5 (13) U6268B In case of a detected overtemperature, only the corresponding channel is disabled. The other channel stays enabled. changing the OCMx resistor. If OUTx is switched off by overtemperature and overcurrent detection, the CLLx output remains logic low (overcurrent). The RETURNx is switched off if the voltage at RETURNx is higher than 2 V (short-circuit comparator threshold) and overtemperature is detected. As the IC is only overtemperature-protected for short-circuit conditions at RETURNx or OUTx, it has to be checked in each application that the chip temperature does not exceed Tjmax = 150°C in normal operation. The OUTx is switched off if the voltage at OCMx is higher than 4.6 V (overcurrent detection 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 Test Hint The overtemperature signal can be activated by connecting ENABLE1 or ENABLE2 to 9 V/ 10 mA. Absolute Maximum Ratings Parameters Supply voltage Voltage at pins CLL1, CLL2, ENABLE1, ENABLE2 Voltage at SC Voltage at OCM1, OCM2 Voltage at RETURN1, RETURN2 Voltage at OUT1, OUT2 Current at supply (both channels OUTx and RETURNx shorted) Current at logical pins: CLL1, CLL2 ENABLE1, ENABLE2 Current at SC (SC related to GND or VBatt) Current at pins to external unit OUT1, OUT2, RETURN1, RETURN2 ESD classification Human body model (100 pF, 1.5 k) Machine model (200 pF, 0.0 ) Ambient temperature range Junction temperature range Storage temperature range Symbol VS VSC VOCMx VRETURNx VOUTx IS ICCLx IENABLEx ISC All pins Tamb Tj Tstg Min. –0.6 –0.3 –0.3 –0.3 –1 –1 Typ. –110 internal limited 2000 200 –40 –40 –55 Max. 40 6 30 6.8 27 40 240 Unit V V V V V V mA 3 0.1 220 mA mA A 95 150 125 V V °C °C °C Thermal Resistance Parameters Junction case Symbol Value Unit RthJC 36 K/W Note: A good thermal resistance junction ambient (RthJA = 65 K/W) can be achieved by using a big pad size for ground connection nearby a metal component (see description of GND-pins). 6 (13) Rev. A3, 11-Apr-01 U6268B Electrical Characteristics Tamb = –40 to 95°C and Tj = –40 to 150°C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VS25 V for max. 25 min, VS40 V for up to 500 ms. The current values are based on R = 750 0%-resistor at OCM1/OCM2 pins. Parameters Supply current Tj 125°C Test Conditions / Pins Symbol Min. Typ. Max. Unit Outputs disabled, VS 18 V IS 8 mA Outputs disabled, VS 40 V IS 14 mA One output enabled, VS 18 V IS 13 mA Both outputs enabled, VS 18 V IS 18 mA Output load 215 mA, VS 18 V IS 56 mA Output load 228 mA, VS 18 V IS 90 mA Output load 250 mA, VS 18 V IS 146 mA Output load 260 mA, VS 18 V (Tj > 125°C) IS 171 mA Both channels OUTx and RETURNx shorted, VS 18 V IS 200 mA Function SC Voltage at SC VS = 5.7 V VSC 5.1 5.3 V Voltage at SC VS = 12.5 V VSC 9 9.4 V Maximal voltage at SC VS = 40 V VSCmax 30 V SC-discharge current Voltage SC = VSC – 3 V 5.7 V VS 40 V ISC_dis 33 82 A Voltage SC = VSC – 3 V 5.7 V VS 40 V ISC_ch –58 –20 A 0.8 3.6 V V SC-charge current Function OUT1 and OUT2 (see figure 4) Voltage difference, VS to VOUTx IOUTx = 5 to 50 mA 5.7 V VS 8.5 V 12 V VS 25 V Vdiff_low Vdiff_high 0.3 2.6 Output voltage OUTx 8.5 V VS 11.3 V VOUT_med 7.7 Maximal voltage at OUTx VS = 40 V VOUT_max 25 30 Current mirror ratio, IOCMx/IOUTx VS 40 V, IOUTx = 5 to 15 mA VS 25 V, IOUTx =15 to 50mA VS 40 V, IOUTx =15 to 50mA IOUT_ratio 0.09 0.10 0.097 0.12 0.11 0.11 Ratio_lin –5 5 % Linearity of mirror ratio IOCMx/IOUTx V V Dynamic resistance OUTx VS 40 V IOUT = 15 to 50 mA ROUT 2 12 Dynamic resistance OUTx + RETURNx VS 40 V IOUT = 15 to 50 mA RDyn 4 15 Rev. A3, 11-Apr-01 7 (13) U6268B Electrical Characteristics (continued) Tamb = –40 to 95°C and Tj = –40 to 150°C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VS25 V for max. 25 min, VS40 V for up to 500 ms. The current values are based on R = 750 0%-resistor at OCM1/OCM2 pins. Parameters Test Conditions / Pins Symbol Min. Typ. Max. Unit OUTx current limitation (OUTx short to GND) VS 18 V VS 40 V IOUT_lim –80 –105 –60 –60 mA mA Overcurrent detection level general Tj < 125°C IOUT_det –70 –51 mA Overcurrent detection level Tj 125°C Always valid: current limitation is higher than overcurrent detection IOUT_det –60 –51 mA Maximum OUTx current (OUTx short to GND) VS = 14 V, OCMx shorted to GND IOUT_max –140 –85 mA Leakage current at disabled OUTx OUTx short to GND, VS 25 V OUTx short to GND, VS 38.5 V IOUT_leak –0.02 –12 Leakage voltage at disabled OUTx OUTx open, VS 38.5 V VOUT_leak Internal pull-down current VS 18 V VS 40 V IOUT_sink Supply rejection-ratio VSC = 7.6 V Vrej_mV Supply rejection-ratio Variation of VS = 8.4 V to 40 V in 10 s Vrej_dB 51.9 dB COUT_min 33 nF Enable_on 3 30 s Enable_off 30 100 s 1.75 1.43 0.26 2.4 1.9 0.6 V V V 0.5 V Minimum capacity at OUTx for phase margin Delay time with Cout = 47 nF Switching on ENABLE = 1 to 90% VOUT reached Switching off ENABLE = 0 to 10% VOUT reached 1.8 2.5 mA mA 4.3 V 4 4.5 mA mA 80 mV Function OCM1, OCM2 Voltage threshold CLLcomparator CLLx low-level voltage threshold CLLx high-level voltage threshold Voltage hysteresis VCLL_L VCLL_H VCLL_hys Minimum voltage at OCMx IOUT = 0 to 5 mA VOCM_min Current-limitation level VS 40 V, OUTx short to GND VOCM_lim 4.3 5.3 V Overcurrent-detection level VS 40 V VOCM_det 4.2 4.9 V Current limitation minus overcurrent detection VOCM_lim – VOCM_over _lim_OCM 0.15 0.5 V IOCM_sink 0.1 0.45 mA 0.5 V Intern. pull-down current Function RETURN1, RETURN2 Enable high saturation voltage 8 (13) IRETURN = 50 mA Vret_sat Rev. A3, 11-Apr-01 U6268B Electrical Characteristics (continued) Tamb = –40 to 95°C and Tj = –40 to 150°C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VS25 V for max. 25 min, VS40 V for up to 500 ms. The current values are based on R = 750 0%-resistor at OCM1/OCM2 pins. Parameters Test Conditions / Pins Symbol Min. Rret Typ. Max. Unit 2 8 Dynamic resistance dI 10 mA Current limitation RETURN is RETURNx i always l higher than current limitation OUTx Enable high, VRETURNx = 2 V Iret_lim 60 150 mA Enable high, VRETURNx 18 V Iret_lim 70 200 mA Enable low VRETURNx 18 V Iret_low 0.8 2 mA Overcurrent-detection level Threshold comparator, switch-off return Threshold comparator, switch-on return Hysteresis Vret_low 1.4 2 V Vret_high 1.1 1.5 V Vret_hys 0.2 0.7 V Switching on IRETURN at 50 mA Switching off IRETURN at 1 mA tdRet_on tdRet_off 3 30 30 90 s s 23.3 19.1 3.5 27.3 22.3 8.2 mA mA mA Delay time CRETURN = 47 nF Function CLL1, CLL2 (CLLx with 2 k to 5 V) IOUT threshold CLL comparator ROCM = 750 CLL low-level threshold CLL high-level threshold Hysteresis ICLL_L ICLL_H ICLL_hys CLL saturation voltage ICLL 2.5 mA VCLL_sat 0.4 V CLL leakage current VCLL 6.5 V ICLL_leak 1 A Response time to current change IOUT to CLL rise IOUT to CLL fall Max. difference between rise and fall time trise-fall 2 2 1 s s s tCLL_rise tCLL–fall 1 1 s s CLL output switching speed Rise Fall tCll_rise tCll_fall 0.1 0.1 Current transmission rate 60 kHz Current transmission 3 dB bandwidth 500 kHz Function ENABLE1, ENABLE2 Enable high–level threshold VEnable_on 2 6.5 V Enable low-level threshold VEnable_off –0.3 0.8 V IEnable 10 100 A Enable input pull-down current (to ensure output disabled during power-off and reset of microcontroller) Rev. A3, 11-Apr-01 9 (13) U6268B Electrical Characteristics (continued) Tamb = –40 to 95°C and Tj = –40 to 150°C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VS25 V for max. 25 min, VS40 V for up to 500 ms. The current values are based on R = 750 0%-resistor at OCM1/OCM2 pins. Parameters Test Conditions / Pins Symbol VS = 18 V, IOUT1 = 28 mA, IOUT2 at overcurrent detection level Min. Typ. Max. Unit Pdis1 1 W Pdis2 0.75 W 165 155 20 °C °C °C Power dissipation Power dissipation 1 Tj 125°C or IOUT2 = 28 mA, IOUT1 at overcurrent detection level Power dissipation 2 Tj 125°C VS = 18 V, IOUT1 = IOUT2 = 28 mA Selective overtemperature protection Logic AND connected with overcurrent detection (RETURNx, OUTx) Switch off Switch on Hysteresis Time delay until overtemperature shut-down VS = 25 V, Tamb = 125°C OUT1 = OUT2 = GND 10 (13) Temp_off Temp_on Temp_hys 155 145 5 tdel 100 ms Rev. A3, 11-Apr-01 U6268B Timing Diagrams VS 14.0 V 12.0 V VSC 10.7 V 8.7 V 0.4 ms VOUTx 10.7 V 0.2 ms 8.7 V t 13841 Figure 5. Variation of power supply VENABLEx 5.0 V IOUTx 75 mA overcurrent overcurrent overcurrent overtemperature shut down 15 mA 100 ms VCLLx 5.0 V Pause / pulse for example 150 ms 75 ms t 13842 (Pulse / pause time depends on power disipation and R thja) Figure 6. Overcurrent protection VENABLEx VOUTx 13 V 60 mA IOUTx 40 mA 10 mA VOCMx 4.7 V 30µs 200 mV overcurrent charge time COUT= 47 nF overcurrent discharge of COUT= 47 nF with internal current 150µs current modulation from sensor 50µs 3.0 V 0.75 V VCLLx 5.0 V 0V t 13840 Figure 7. Data transmission Rev. A3, 11-Apr-01 11 (13) U6268B Application Circuit +VBatt nF 22 F VCC = 5 V Sensor 1 4 VS 14 I/O 15 I/O 13 Out1 CLL1 Interface1 47 nF Enable1 OCM1 5V 3 Return1 2 750 C 47 nF U6268B VCC = 5 V Out2 11 I/O 10 I/O 750 CLL2 Sensor 2 5V 5 47 nF Interface2 Enable2 12 OCM2 GND 1, 8, 9, 16 Return2 SC 6 7 47 nF 22 nF 96 11710 Figure 8. Application circuit Package Information Package SO16 Dimensions in mm 5.2 4.8 10.0 9.85 3.7 1.4 0.25 0.10 0.4 1.27 6.15 5.85 8.89 16 0.2 3.8 9 technical drawings according to DIN specifications 1 12 (13) 13036 8 Rev. A3, 11-Apr-01 U6268B Ozone Depleting Substances Policy Statement It is the policy of Atmel Germany 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. Atmel Germany GmbH 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. Atmel Germany GmbH 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 Atmel Wireless & Microcontrollers products for any unintended or unauthorized application, the buyer shall indemnify Atmel Wireless & Microcontrollers 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. Data sheets can also be retrieved from the Internet: http://www.atmel–wm.com Atmel Germany GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany Telephone: 49 (0)7131 67 2594, Fax number: 49 (0)7131 67 2423 Rev. A3, 11-Apr-01 13 (13)