U6268B

Preliminary Information

TELEFUNKEN Semiconductors
Rev. A1, 21-May-97

1 (12)

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 U6228B 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 micro-

controller input

D Operation supply voltage range 5.7 V v V

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

Ordering Information

Extended Type Number

Package

Remarks

U6268B

SO16

Block Diagram

Short circuit

detection

Temperature

monitor

Smoothed voltage

regulator

I/U converter

Smoothed voltage

regulator

I/U converter

Voltage

comparator

Channel 1

Data

Enable

Voltage

comparator

Channel 2

Data

Crash

sensor

Channel 1

Channel 2

Channel 1
power

supply

Data

trans
mission

Crash

sensor

Channel 2
power
supply

Data
trans
mission

13839

Figure 1. Block diagram

U6268B

TELEFUNKEN Semiconductors

Rev. A1, 21-May-97

Preliminary Information

2 (12)

Pin Description

OUT1

OUT2

RETURN2

GND

RETURN1

13321

CLL1

OCM1

OCM2

CLL2

ENABLE2

GND

ENABLE1

Figure 2. Pinning

Symbol

Function

GND

Ground and reference pin

RETURN1

Return line of the external unit,
internally connected to GND via
a line-protection transistor

OUT1

Voltage-stabilized supply output
and current-modulation input

Supply voltage of the IC

OUT2

Voltage stabilized supply output
and current modulation input

Smooth time constant for slow
voltage change at both OUT
pins

RETURN2

Return line of the external unit,
internally connected to GND via
a line-protection transistor

8, 9

GND

Ground and reference pin

ENABLE1

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

OCM2

Analog current output, repre-
senting 1/10 current of OUT2

OCM1

Analog current output, repre-
senting 1/10 current of OUT1

CLL1

Current logic level output, low
at high OUT1 current, moni-
toring via OCM1

ENABLE2

Controls OUT2 voltage,
ENABLE2 High means OUT2
active, ENABLE1 Low or open
means OUT2 switched off

GND

Ground and reference pin

Figure 3. Application circuit

Functional Description

The IC and the external units are powered via the V

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.

OUT1, OUT2

OUTx provides a smoothed, very slowly changing supply

voltage for the external units and monitors the output cur-
rent. During normal operating conditions, the OUTx
voltage is typ. 3 V below V

, and changes very slowly

with a varying battery voltage in order to suppress distur-
bances in the data transmission. At low V

(5.7 to 8.5 V),

the OUTx voltage is typ. 0.5 V below V

. 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.

U6268B

Preliminary Information

TELEFUNKEN Semiconductors
Rev. A1, 21-May-97

3 (12)

( V )

13322

out

22.4

21.4

9.4

8.2

5.4

4.9

7.7

5.7

8.5

11.3 12.0

28.6

32.6

Vout max

Vout min

(

)

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 current-
monitoring 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 V

(Pin 4) en-

sures that no current is fed back to the V

Batt

-system in the

case of a short between OUTx and V

Batt

. A minimum ca-

pacity of 33 nF is required at the pins OUTx .

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

the related OUTx and RETURNx off (high imped-
ance). A sink current at Pin OUTx discharges the
capacitive load.

D High applied to ENABLEx switches the related

OUTx and RETURNx on to supply the external unit.

OCM1, OCM2

The output current of OUTx is monitored with a transmis-
sion factor of 0.1 to the OCMx. With a resistor from OCM
to GND, the current is converted to a voltage. The electri-
cal characteristics are specified by R

OCM

= 750

W. The

CLL-current threshold, the OUT-current limitation and
the OUT-current detection can be changed by varying
R

OCM

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 cir-
cuit to V

Batt

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-tran-
sistor with typically 0.1 V. The maximum voltage at
OCM is limited by an internal clamping diode to 5.3 V.

CLL1, CLL2

The current at Pin OUTx is logical evaluated and ready
to use for a microcontroller input. With this stage, the

U6268B

TELEFUNKEN Semiconductors

Rev. A1, 21-May-97

Preliminary Information

4 (12)

logic data transmission from the external unit to the inter-
face 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 R

OCMx

= 750

W at OCMx, the

correct OUTx-current threshold related to the logical out-
put 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 R

OCM

resistor is assumed to be 0%.

The CLL-pin is an open-collector output and needs a
pull-up resistor of typically 2 k

W 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 satu-
ration voltage less than 0.5 V at I

RETURNx

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.

The smooth capacitor is designed to realize the long-time
constant for the slow voltage change at OUTx for both in-
terface channels. The capacity is typ. 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.

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, R

thJC

. In order to achieve

a good thermal resistance, R

thJA,

a good copper connec-

tion from the four GND pins to the metal parts of the
modul housing is also recommended.

Power Dissipation

Worst case calculation of the supply current I

= 1,278

( I

OUT1

+ I

OUT2

) + 18 mA

Worst case calculation of the IC's power dissipation P

= (V

) [(V

diff

ret-sat

)

OUT1

+ I

OUT2

)

OCM

((I

OUT1

+ I

OUT2

) / 81)]

= supply voltage 5.7 to 25 V

voltage difference V

to V

OUTx

diff

= 3.6 at 12 V

v 25 V

diff

= 0.8 at 5.7 V

v 8.5 V

ret-sat

= 0.5 V saturation voltage return

OUTx

= output current at Pin OUTx = 0 to 60 mA

OCM

= resistor at Pin OCMx

Selective Overtemperature Protection

An overtemperature protection is integrated which gene-
rates a switch-off signal at a chip temperature of typically
T

= 160

C and a switch-on signal at typically T

= 150

In case of a detected overtemperature, only the corre-
sponding channel is disabled. The other channel stays
enabled.

The RETURNx is switched off if the voltage at RE-
TURNx 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 over-
temperature 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-cir-
cuit conditions at RETURNx or OUTx, it has to be
checked in each application that the chip temperature
does not exceed T

jmax

= 150

C in normal operation.

Test Hint

The overtemperature signal can be activated by con-nect-
ing ENABLE1 or ENABLE2 to 9 V/ 10 mA.

U6268B

Preliminary Information

TELEFUNKEN Semiconductors
Rev. A1, 21-May-97

5 (12)

Absolute Maximum Ratings

Parameters

Symbol

Min.

Typ.

Max.

Unit

Supply voltage

0.6

Voltage at pins CLL1, CLL2, ENABLE1, ENABLE2

0.3

Voltage at SC

0.3

Voltage at OCM1, OCM2

OCMx

0.3

6.8

Voltage at RETURN1, RETURN2

RETURNx

Voltage at OUT1, OUT2

OUTx

Current at supply
(both channels OUTx and RETURNx shorted)

240

Current at logical pins: CLL1, CLL2

ENABLE1, ENABLE2

CCLx

ENABLEx

0.1

mA
mA

Current at SC (SC related to GND or V

Batt

)

110

220

Current at pins to external unit

OUT1, OUT2, RETURN1, RETURN2

internal

limited

ESD classification

Human body model (100 pF, 1.5 k

Machine model (200 pF, 0.0

All pins

"2000

"200

V
V

Ambient temperature range

amb

Junction temperature range

150

Storage temperature range

stg

125

Thermal Resistance

Parameters

Symbol

Value

Unit

Junction to pin

thJC

k/W

Junction ambient is reachable with a big pad size for
GND near a screw or the metal housing

thJA

k/W

Electrical Characteristics

amb

= 40 to 95

C and T

= 40 to 150

operation supply voltage range 5.7 to 18 V continuously,

v25 V for max. 25 min, v40 V for up to 500 ms.

The current values are based on the 750

W 0% resistor at OCM1/OCM2

Parameters

Test Conditions / Pins

Symbol

Min.

Typ.

Max.

Unit

Supply current
T

125

Outputs disabled, V

v 18 V

pp y

w 125

Outputs disabled, V

v 40 V

One output enabled, V

v 18 V

Both outputs enabled, V

v 18 V

Output load 2

15 mA, V

v18 V

Output load 2

28 mA, V

v18 V

Output load 2

50 mA, V

v18 V

146

Output load 2

60 mA,

v 18 V (T

> 125

171

Both channels OUTx and
RETURNx shorted, V

v 18 V

200

Function SC

U6268B

TELEFUNKEN Semiconductors

Rev. A1, 21-May-97

Preliminary Information

6 (12)

Unit

Max.

Typ.

Min.

Symbol

Test Conditions / Pins

Parameters

Voltage at SC

= 5.7 V

5.1

5.3

Voltage at SC

= 12.5 V

9.4

Maximal voltage at SC

= 40 V

SCmax

SC-discharge current

Voltage SC = V

3 V

5.7 V

v V

v 40 V

SC_dis

SC-charge current

Voltage SC = V

3 V

5.7 V

v V

v 40 V

SC_ch

Function OUT1 and OUT2 (see figure 4)

Voltage difference,
V

to V

OUTx

= 5 to 50 mA

5.7 V

v V

v 8.5 V

12 V

v V

v 25 V

diff_low

diff_high

0.3
2.6

0.8
3.6

V
V

Output voltage OUTx

8.5 V

v V

v 11.3 V

OUT_med

7.7

Maximal voltage at
OUTx

= 40 V

OUT_max

Current mirror ratio,
I

OCMx

OUTx

v 40 V, I

OUTx

= 5 to 15 mA

v 25 V, I

OUTx

=15 to 50mA

v 40 V, I

OUTx

=15 to 50mA

OUT_ratio

0.09
0.10

0.097

0.12
0.11
0.11

Linearity of mirror ratio
I

OCMx

OUTx

Ratio_lin

Dynamic resistance
OUTx

v 40 V I

OUT

= 15 to 50 mA

OUT

Dynamic resistance
OUTx + RETURNx

v 40 V I

OUT

= 15 to 50 mA

Dyn

OUTx current limitation
(OUTx short to GND)

v 18 V

v 40 V

OUT_lim

105

60
60

mA
mA

Overcurrent detection
level general

< 125

OUT_det

Overcurrent detection
level

w 125

Always valid: current limitation is
higher than overcurrent detection

OUT_det

Maximum OUTx current
(OUTx short to GND)

= 14 V, OCMx shorted to GND

OUT_max

140

Leakage current at
disabled OUTx

OUT short to GND V

v 25 V

OUT short to GND V

v 38.5 V

OUT_leak

0.02

mA
mA

Leakage voltage at
disabled OUTx

OUT open V

v 38.5 V

OUT_leak

4.3

Internal pull-down
current

v 18 V

v 40 V

OUT_sink

1.8
2.5

4.5

mA
mA

Supply rejection-ratio

= 7.6 V

rej_mV

Supply rejection-ratio

Variation of V

8.4 to 40 V

in 10

rej_dB

51.9

Minimum capacity at
OUTx for phase margin

OUT_min

Delay time with
C

out

= 47 nF

Switching on ENABLE = 1 to
90% V

OUT

reached

Switching off ENABLE = 0 to
10% V

OUT

reached

Enable_on

Enable_off

100

Function OCM1, OCM2

U6268B

Preliminary Information

TELEFUNKEN Semiconductors
Rev. A1, 21-May-97

7 (12)

Unit

Max.

Typ.

Min.

Symbol

Test Conditions / Pins

Parameters

Voltage threshold CLL-
comparator

CLLx low-level voltage threshold

CLLx high-level voltage threshold

Voltage hysteresis

CLL_L

CLL_H

CLL_hys

1.75
1.43
0.26

2.4
1.9
0.6

V
V
V

Minimal voltage at
OCMx

OUT

= 0 to 5 mA

OCM_min

0.5

Current-limitation level

v 40 V OUTx short to GND

OCM_lim

4.3

5.3

Overcurrent-detection
level

v 40 V

OCM_det

4.2

4.9

Current limitation minus
overcurrent detection

OCM_lim

OCM_over

D_lim_OCM

0.15

0.5

Intern. pull-down current

OCM_sink

0.1

0.45

Function RETURN1, RETURN2

Enable high saturation
voltage

RETURN

= 50 mA

ret_sat

0.5

Dynamic resistance

w 10 mA

ret

Current limitation

Enable high, V

RETURNx

= 2 V

ret_lim

150

RETURNx is always
higher than current

Enable high, V

RETURNx

v 18 V

ret_lim

200

higher than current
limitation OUTx

Enable low V

RETURNx

v 18 V

ret_lim

0.8

Overcurrent-detection
level

Threshold comparator, switch-off
return
Threshold comparator, switch-on
return
Hysteresis

ret_low

ret_high

ret_hys

1.4

1.1

0.2

1.5

0.7

Delay time
C

RETURN

= 47 nF

Switching on I

RETURN

at 50 mA

Switching off I

RETURN

at 1 mA

dRet_on

dRet_off

Function CLL1, CLL2 (CLLx with 2 k

W to 5 V)

OUT

threshold CLL

comparator

OCM

= 750

CLL low-level threshold
CLL high-level threshold
Hysteresis

CLL_L

CLL_H

CLL_hys

23.3
19.1

3.5

27.3
22.3

8.2

mA
mA
mA

CLL saturation voltage

CLL

v 2.5 mA

CLL_sat

0.4

CLL leakage current

CLL

v 6.5 V

CLL_leak

Response time to current
change

OUT

to CLL rise

OUT

to CLL fall

Max. difference between rise and
fall time

Cll_rise

Cll_fall

D rise-fall

0.1
0.1

2
2
1

CLL output switching
speed

Rise
Fall

CLL_rise

CLLfall

1
1

Current transmission rate

kHz

Current transmission
3 dB bandwidth

500

kHz

Function ENABLE1, ENABLE2

Enable lowlevel
threshold

Enable_off

6.5

Enable high-level
threshold

Enable_on

0.3

0.8

U6268B

TELEFUNKEN Semiconductors

Rev. A1, 21-May-97

Preliminary Information

8 (12)

Unit

Max.

Typ.

Min.

Symbol

Test Conditions / Pins

Parameters

Enable input pull-down
current (to ensure output
disabled during power-off
and reset of micro-
controller)

Enable

100

Power dissipation

Power dissipation 1
T

w 125

= 18 V,

OUT1

= 28 mA,

OUT2

at overcurrent detection level

Pdis1

or
I

OUT2

= 28 mA,

OUT1

at overcurrent detection level

Power dissipation 2
T

w 125

= 18 V,

OUT1

= I

OUT2

= 28 mA

Pdis2

0.75

Selective overtemperature protection

Logic AND connected
with overcurrent detec-
tion (RETURNx, OUTx)

Switch off
Switch on
Hysteresis

Temp_off

Temp_on

Temp_hys

155
145

165
155

Time delay until over-
temperature shut-down

= 25 V, T

amb

= 125

OUT1 = OUT2 = GND

del

100

Timing Diagrams

14.0 V

12.0 V

Supply

10.7 V

8.7 V

10.7 V

8.7 V

OUTx

0.4 ms

0.2 ms

13841

Figure 5. Variation of power supply

U6268B

TELEFUNKEN Semiconductors

Rev. A1, 21-May-97

Preliminary Information

12 (12)

Ozone Depleting Substances Policy Statement

It is the policy of TEMIC TELEFUNKEN microelectronic 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.

TEMIC TELEFUNKEN microelectronic GmbH semiconductor division 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.

TEMIC 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 TEMIC products for any unintended or unauthorized

application, the buyer shall indemnify TEMIC 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.

TEMIC TELEFUNKEN microelectronic GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany

Telephone: 49 ( 0 ) 7131 67 2831, Fax number: 49 ( 0 ) 7131 67 2423

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