U6268B Datasheet, PDF (5/14 Pages) TEMIC Semiconductors – Side-Airbag Sensor Dual Interface

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 R_OCM = 750Ω. The CLL-current threshold, the OUT-current limitation and the
OUT-current detection can be changed by varying R_OCM 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 V_Batt 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 R_OCMx = 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 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.
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 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.
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4808B–AUTO–09/05