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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
D Two identical interface channels D Provides a pre-regulated smoothed voltage and a supply current up to 50 mA for the sensors D Receives data from the sensors by current modulation with a transmission rate of 60 kBaud (transmission bandwidth 500 kHz) D Current modulation provides high noise immunity for data transfer D TTL-compatible input activate the sensor D Data output can be directly connected to a microcontroller input D Operation supply voltage range 5.7 V v VS v 40 V D ESD protection according to MIL-STD-883C test method 3015.7 D High-level EMI protection
Benefits
D Voltage supply and data transmission with one active wire over long distances
Block Diagram
Data Channel 1 Enable Voltage comparator I/V converter Smoothed voltage regulator Channel 1 power supply Data trans- mission Crash sensor
C
Enable Channel 2 Data
Channel 1 Channel 2
Temperature monitor
Short circuit detection Channel 2 power supply Data trans- mission
Smoothed voltage regulator Voltage comparator I/V converter
Crash sensor
13839
Figure 1. Block diagram
Ordering Information
Extended Type Number U6268B-FP Package SO16 Remarks
Rev. A3, 11-Apr-01
1 (13)
U6268B
Pin Description
Pin 1 GND 1 16 GND 15 ENABLE1 3 OUT1 3 VS 4 14 CLL1 4 13 OCM1 12 OCM2 11 CLL2 10 ENABLE2 8, 9 GND 8
13321
Symbol GND
Function Ground and reference pin
2
RETURN1 2
RETURN1 Return line of the external unit, internally connected to GND via a line-protection transistor OUT1 VS OUT2 SC Voltage-stabilized supply output and current-modulation input Supply voltage of the IC Voltage stabilized supply output and current modulation input Smooth time constant for slow voltage change at both OUT pins
5 6
OUT2 5 SC 6 RETURN2 7
7
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 CLL2 Current logic level output, low at high OUT2 current, monitoring via OCM2 Analog current output, representing 1/10 current of OUT2 Analog current output, representing 1/10 current of OUT1 Current logic level output, low at high OUT1 current, monitoring via OCM1
9
GND
10
Figure 2. Pinning
11
12 13 14
OCM2 OCM1 CLL1
15
ENABLE1 Controls OUT2 voltage, ENABLE2 High means OUT2 active, ENABLE1 Low or open means OUT2 switched off GND Ground and reference pin
16
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U6268B
VS Slew rate Vout 5 V/ms @ VS rising 10 V/ms @ VS falling VS VSC VS Isc-ch VSC - + + - Iout Over current limi- tation OUTx
Voltage Regulator
Current mirror ratio Iocmx / Ioutx
SC
Vout ON OFF
Isc-dis
Iout-sink
Temperature protection high T > 165C low T < 145C ENABLEx
High = ENABLE OUTx
Temp
Latch Reset Set -+ Vocm-det + - Vcll-x Iocm-sink Vret_x - + + - RETURNx 3 Current limitation -+ 4.2 V Vocm-lim OCMx
Test mode If ENABLE x = 9 V then Temp = high CLLx Temp
Iret-low
GND
13948
Figure 3. Functional block diagram
Rev. A3, 11-Apr-01
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U6268B
Functional Description
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 mF smoothes the voltage and absorbes positive and negative transients. 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.
OUT1, OUT2
OUTx provides a smoothed, very slowly changing supply
35 Vout max 30 Vout min 25 Vout ( V ) 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 VS ( V )
25 28.6
30 32.6
35
40
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 ms, 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
OUTx may not exceed 12 W inside the bandwidth range (total of 15 W 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.
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U6268B
ENABLE1, ENABLE2
ENABLEx is a microcontroller-compatible input which switches the related output on or off. D 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. D 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 kW 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 v 50 mA. If ENABLEx is low or open, RETURNx is a current sink with v 2 mA. RETURNx is current-limited at typically 150 mA.
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 ROCM = 750 W. The CLL-current threshold, the OUT-current limitation and the OUT-current detection can be changed by varying ROCM in a range from 500 W to 1 kW. 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.
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 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.
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.
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-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 W 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%.
Power Dissipation
Worst case calculation of the supply current IS: IS = 1,278 ( IOUT1 + IOUT2 ) + 18 mA
Worst case calculation of the IC's power dissipation PV: PV = (VS IS) - [(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 vVS v 25 V Vdiff = 0.8 V at 5.7 V vVS v 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 = 160C and a switch-on signal at typically Tj = 150C.
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U6268B
In case of a detected overtemperature, only the corresponding channel is disabled. The other channel stays enabled. The RETURNx is switched off if the voltage at RETURNx is higher than 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 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 changing the OCMx resistor. If OUTx is switched off by overtemperature and overcurrent detection, the CLLx output remains logic low (overcurrent). 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 = 150C in normal operation.
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 kW) Machine model (200 pF, 0.0 W) Ambient temperature range Junction temperature range Storage temperature range Symbol VS VSC VOCMx VRETURNx VOUTx IS ICCLx IENABLEx ISC Min. -0.6 -0.3 -0.3 -0.3 -1 -1 Typ. Max. 40 6 30 6.8 27 40 240 3 0.1 220 Unit V V V V V V mA mA mA mA
-110 internal limited "2000 "200 -40 -40 -55
All pins
Tamb Tj Tstg
95 150 125
V V C C C
Thermal Resistance
Parameters Junction case Symbol RthJC Value 36 Unit 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).
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U6268B
Electrical Characteristics
Tamb = -40 to 95C and Tj = -40 to 150C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VSv25 V for max. 25 min, VSv40 V for up to 500 ms. The current values are based on R = 750 W, 0%-resistor at OCM1/OCM2 pins. Parameters Supply current Tj w 125C Test Conditions / Pins Outputs disabled, VS v 18 V Outputs disabled, VS v 40 V One output enabled, VS v 18 V Both outputs enabled, VS v 18 V Output load 2 Output load 2 Output load 2 15 mA, VS v18 V 28 mA, VS v18 V 50 mA, VS v18 V Symbol IS IS IS IS IS IS IS IS IS Min. Typ. Max. 8 14 13 18 56 90 146 171 200 Unit mA mA mA mA mA mA mA mA mA
Output load 2 60 mA, VS v 18 V (Tj > 125C) Both channels OUTx and RETURNx shorted, VS v 18 V Function SC Voltage at SC Voltage at SC Maximal voltage at SC SC-discharge current SC-charge current VS = 5.7 V VS = 12.5 V VS = 40 V Voltage SC = VSC - 3 V 5.7 V v VS v 40 V Voltage SC = VSC - 3 V 5.7 V v VS v 40 V IOUTx = 5 to 50 mA 5.7 V v VS v 8.5 V 12 V v VS v 25 V 8.5 V v VS v 11.3 V VS = 40 V VS v 40 V, IOUTx = 5 to 15 mA VS v 25 V, IOUTx =15 to 50mA VS v 40 V, IOUTx =15 to 50mA
VSC VSC VSCmax ISC_dis ISC_ch
5.1 9
5.3 9.4 30
V V V mA mA
33 -58
82 -20
Function OUT1 and OUT2 (see figure 4) Voltage difference, VS to VOUTx Output voltage OUTx Maximal voltage at OUTx Current mirror ratio, IOCMx/IOUTx Linearity of mirror ratio IOCMx/IOUTx Dynamic resistance OUTx Dynamic resistance OUTx + RETURNx VS v 40 V IOUT = 15 to 50 mA VS v 40 V IOUT = 15 to 50 mA Vdiff_low Vdiff_high VOUT_med VOUT_max 0.3 2.6 7.7 25 0.09 0.10 0.097 -5 2 4 30 0.12 0.11 0.11 5 12 15 % W W 0.8 3.6 V V V V
IOUT_ratio Ratio_lin ROUT RDyn
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U6268B
Electrical Characteristics (continued)
Tamb = -40 to 95C and Tj = -40 to 150C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VSv25 V for max. 25 min, VSv40 V for up to 500 ms. The current values are based on R = 750 W, 0%-resistor at OCM1/OCM2 pins. Parameters OUTx current limitation (OUTx short to GND) Overcurrent detection level general Overcurrent detection level Maximum OUTx current (OUTx short to GND) Leakage current at disabled OUTx Leakage voltage at disabled OUTx Internal pull-down current Supply rejection-ratio Supply rejection-ratio 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 CLLx low-level voltage threshold CLLx high-level voltage threshold Voltage hysteresis IOUT = 0 to 5 mA VS v 40 V, OUTx short to GND VS v 40 V VOCM_lim - VOCM_over Test Conditions / Pins VS v 18 V VS v 40 V Tj < 125C Tj w 125C Always valid: current limitation is higher than overcurrent detection VS = 14 V, OCMx shorted to GND OUTx short to GND, VS v 25 V OUTx short to GND, VS v 38.5 V OUTx open, VS v 38.5 V VS v 18 V VS v 40 V VSC = 7.6 V Variation of VS = 8.4 V to 40 V in 10 ms Symbol IOUT_lim IOUT_det IOUT_det Min. -80 -105 -70 -60 Typ. Max. -60 -60 -51 -51 Unit mA mA mA mA
IOUT_max IOUT_leak VOUT_leak IOUT_sink Vrej_mV Vrej_dB COUT_min Enable_on Enable_off
-140 -0.02 -12
-85
mA mA mA
4.3 1.8 2.5 51.9 33 3 30 30 100 4 4.5 80
V mA mA mV dB nF ms ms
Function OCM1, OCM2 Voltage threshold CLLcomparator Minimum voltage at OCMx Current-limitation level Overcurrent-detection level Current limitation minus overcurrent detection Intern. pull-down current Function RETURN1, RETURN2 Enable high saturation voltage IRETURN = 50 mA Vret_sat 0.5 V VCLL_L VCLL_H VCLL_hys VOCM_min VOCM_lim VOCM_det D_lim_OCM IOCM_sink 4.3 4.2 0.15 0.1 1.75 1.43 0.26 2.4 1.9 0.6 0.5 5.3 4.9 0.5 0.45 V V V V V V V mA
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U6268B
Electrical Characteristics (continued)
Tamb = -40 to 95C and Tj = -40 to 150C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VSv25 V for max. 25 min, VSv40 V for up to 500 ms. The current values are based on R = 750 W, 0%-resistor at OCM1/OCM2 pins. Parameters Dynamic resistance Current limitation RETURNx is l RETURN i always higher than current limitation OUTx Overcurrent-detection level Test Conditions / Pins dI w 10 mA Enable high, VRETURNx = 2 V Enable high, VRETURNx v 18 V Enable low VRETURNx v 18 V Threshold comparator, switch-off return Threshold comparator, switch-on return Hysteresis Switching on IRETURN at 50 mA Switching off IRETURN at 1 mA ROCM = 750 W CLL low-level threshold CLL high-level threshold Hysteresis ICLL v 2.5 mA VCLL v 6.5 V IOUT to CLL rise IOUT to CLL fall Max. difference between rise and fall time Rise Fall Symbol Rret Iret_lim Iret_lim Iret_low Vret_low Vret_high Vret_hys tdRet_on tdRet_off Min. 2 60 70 0.8 1.4 1.1 0.2 3 30 Typ. Max. 8 150 200 2 2 1.5 0.7 30 90 Unit W mA mA mA V V V ms ms
Delay time CRETURN = 47 nF IOUT threshold CLL comparator
Function CLL1, CLL2 (CLLx with 2 kW to 5 V) ICLL_L ICLL_H ICLL_hys VCLL_sat ICLL_leak tCll_rise tCll_fall tD rise-fall tCLL_rise tCLL-fall 60 500 0.1 0.1 23.3 19.1 3.5 27.3 22.3 8.2 0.4 1 2 2 1 1 1 mA mA mA V mA ms ms ms ms ms kHz kHz
CLL saturation voltage CLL leakage current Response time to current change
CLL output switching speed Current transmission rate Current transmission 3 dB bandwidth
Function ENABLE1, ENABLE2 Enable high-level threshold Enable low-level threshold Enable input pull-down current (to ensure output disabled during power-off and reset of microcontroller) VEnable_on VEnable_off IEnable 2 -0.3 10 6.5 0.8 100 V V mA
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U6268B
Electrical Characteristics (continued)
Tamb = -40 to 95C and Tj = -40 to 150C, Operation supply-voltage range VS = 5.7 to 18 V continuously, VSv25 V for max. 25 min, VSv40 V for up to 500 ms. The current values are based on R = 750 W, 0%-resistor at OCM1/OCM2 pins. Parameters Power dissipation Power dissipation 1 Tj w 125C VS = 18 V, IOUT1 = 28 mA, IOUT2 at overcurrent detection level or IOUT2 = 28 mA, IOUT1 at overcurrent detection level Power dissipation 2 Tj w 125C Logic AND connected with overcurrent detection (RETURNx, OUTx) Time delay until overtemperature shut-down VS = 18 V, IOUT1 = IOUT2 = 28 mA Switch off Switch on Hysteresis VS = 25 V, Tamb = 125C OUT1 = OUT2 = GND Pdis2 0.75 W Pdis1 1 W Test Conditions / Pins Symbol Min. Typ. Max. Unit
Selective overtemperature protection Temp_off Temp_on Temp_hys tdel 155 145 5 100 165 155 20 C C C ms
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U6268B
Timing Diagrams
VS 14.0 V 12.0 V
VSC 10.7 V 8.7 V 0.4 ms 0.2 ms
VOUTx 10.7 V 8.7 V
t
13841
Figure 5. Variation of power supply
VENABLEx 5.0 V IOUTx 75 mA 15 mA 100 ms VCLLx 5.0 V Pause / pulse for example overcurrent overtemperature shut down overcurrent overcurrent
150 ms
75 ms
t
13842
(Pulse / pause time depends on power disipation and R thja)
Figure 6. Overcurrent protection
VENABLEx
VOUTx 13 V
30s 200 mV
discharge of COUT= 47 nF with internal current
60 mA IOUTx 40 mA 10 mA VOCMx 4.7 V 3.0 V 0.75 V VCLLx 5.0 V 0V
overcurrent charge time COUT= 47 nF overcurrent current modulation from sensor 50s
150s
t
13840
Figure 7. Data transmission
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U6268B
Application Circuit
+V Batt 100 nF VCC = 5 V 4 VS I/O I/O 14 15 13 750 CLL1 Out1 22 mF
Sensor 1
3 47 nF Return1 2 47 nF 5V
Interface1
Enable1 OCM1
mC
I/O I/O
VCC = 5 V
U6268B
Out2 11 10 CLL2 Enable2 Return2 SC 6 7 5
Sensor 2
5V
Interface2
47 nF
750
12 OCM2 GND 1, 8, 9, 16
47 nF 22 nF
96 11710
Figure 8. Application circuit
Package Information
Package SO16
Dimensions in mm
10.0 9.85 5.2 4.8 3.7
1.4 0.4 1.27 8.89 16 9 0.25 0.10 0.2 3.8 6.15 5.85
technical drawings according to DIN specifications
13036
1
8
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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
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