u6268b ATMEL Corporation, u6268b Datasheet - Page 5

• Manufacturer Part Number: u6268b
• Description: U6268b Side-airbag Sensor Dual Interface
• Manufacturer: ATMEL Corporation

3.3
3.4
3.5
3.6
3.7
4808B–AUTO–09/05
ENABLE1, ENABLE2
OCM1, OCM2
CLL1, CLL2
RETURN 1, RETURN 2
SC
ENABLEx is a microcontroller-compatible input which switches the related output on or off.
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
OUT-current detection can be changed by varying R
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
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.
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
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.
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 is current-limited at typically 150 mA.
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
the maximum slew rate is V
is V
• A low or open circuit applied to ENABLEx switches off the related OUTx and RETURNx (high
• A high applied to ENABLEx switches on the related OUTx and RETURNx to supply the
impedance). A sink current at pin OUTx discharges the capacitive load.
external unit.
OUTx
= 10 V/ms.
RETURNx
50 mA. If ENABLEx is low or open, RETURNx is a current sink with
OCM
= 750 . The CLL-current threshold, the OUT-current limitation and the
OUTx
OCMx
= 5 V/ms, and at the falling edge of V
= 750 at OCMx, the correct OUTx-current threshold related
OCM
in a range of 500 to 1 k .
Batt
, the maximum slew rate
Batt
or open load).
U6268B
2 mA.
Batt
5
,