u6268b ATMEL Corporation, u6268b Datasheet - Page 4

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

3. Functional Description
3.1
3.2
4
V
OUT1, OUT2
U6268B
S
The IC and the external units are powered via the V
via a reverse battery protection diode. An electrolythic capacitor of 22 µF smoothes the voltage
and absorbs positive and negative transients.
OUTx provides a smoothed, very slowly changing supply voltage for the external units and mon-
itors the output current. During normal operating conditions, the OUTx voltage is typically 3V
below V
bances in the data transmission. At low V
below V
nal unit between OUTx and RETURNx. The output current capability is 50 mA. The internal pull-
down current at OUTx is typically 3 mA.
Figure 3-1.
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 the CLL pin. The external unit can
switch on an additional current of 30 mA, interpreted by the interface as logic low. The slope
time of the current pulse is approximately 1 µs which is suitable for a transmission rate up to
60 kBaud. The necessary transmission bandwidth of greater than 500 kHz between OUTx and
OCMx is guaranteed (see
sion behavior, the dynamic resistance of OUTx may not exceed 12 within 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 protected against overtemperature and short circuits. A reverse polarity diode
at pin V
between OUTx and V
S
S
S
. This voltage difference is reduced in to ensure sufficient supply voltage for the exter-
, and changes very slowly with a varying battery voltage in order to suppress distur-
(pin 4) ensures that no current is fed back to the V
Output Voltage with Tolerances versus Supply Voltage
8.2
5.4
Batt
21.4
22.4
7.7
9.4
4.9
. A minimum capacity of 33 nF is required at the pins OUTx.
“Application Circuit” on page
30
20
35
25
10
15
0
5
0
5
5.7
8.5
10
S
11.3
(5.7V to 8.5V), the OUTx voltage is typically 0.5V
12.0
15
S
V
pin 4. This pin is connected to the battery
20
S
(V)
12). To achieve good current transmis-
25
Batt
system in the case of a short
28.6
30
32.6
Voutmax
Voutmin
35
40
4808B–AUTO–09/05