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PDF U6268B Data sheet ( Hoja de datos )
| Número de pieza | U6268B | |
| Descripción | Side-airbag Sensor Dual Interface | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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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 5.7V ≤ VS ≤ 40V
• 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
Side-airbag
Sensor Dual
Interface
U6268B
1. 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 sensors and receive digital information from
them via one active wire each. The interface supplies the external sensors with a pre-
www.DataSheet4U.com
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 1-1. Block Diagram
Data
Channel 1
Enable
Voltage
comparator
Channel 1
Channel 2
Enable
Channel 2
Data
Voltage
comparator
I/V converter
Smoothed voltage
regulator
Temperature Short circuit
monitor
detection
Smoothed voltage
regulator
I/V converter
Channel 1
power
supply
Data
trans-
mission
Crash
sensor
Channel 2
power
supply
Data
trans-
mission
Crash
sensor
Rev. 4808B–AUTO–09/05
1 page  
U6268B
3.3 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.
3.4 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 = 750Ω. The CLL-current threshold, the OUT-current limitation and the
OUT-current detection can be changed by varying ROCM in a range of 500Ω to 1 kΩ.
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 VBatt or open load).
The internal pull-down current at OUTx creates no OCMx-current. During ENABLE, the mini-
mum voltage at OCMx is the saturation voltage of an internal NPN-transistor with typically 0.1V.
The maximum voltage at OCM is limited by an internal clamping diode to 5.3V.
3.5 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 2.4V creates a logic low at CLLx, and a OCMx voltage lower than
1.43V creates a logic high at CLLx. The comparator has an internal hysteresis of typically 0.4V.
With the pull-down resistor ROCMx = 750Ω 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 kΩ to the 5-V
supply. For ESD protection, a 7-V Zener diode is implemented.
3.6 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 of less than
0.5V 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.
3.7 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 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.
4808B–AUTO–09/05
5
5 Page 
7. Timing Diagrams
Figure 7-1. Variation of Power Supply
VS
14.0 V
12.0 V
VSC 10.7 V
8.7 V
VOUTx
10.7 V
8.7 V
0.4 ms
0.2 ms
t
Figure 7-2. Overcurrent Protection
VENABLEx
5.0 V
IOUTx
75 mA
15 mA
VCLLx
5.0 V
overcurrent
overcurrent
100 ms
overtemperature
shut down
Pause/pulse for example
overcurrent
150 ms
75 ms
(Pulse/pause time depends on power disipation and RthJA)
t
U6268B
4808B–AUTO–09/05
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet U6268B.PDF ] | |
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