U243B
Warning or Car-Direction Indicator
Technology:
Bipolar
Features
D
Can be protected against damage or interference with
a minimum of external circuitry
D
Voltage dependence of the car indicator lamps also
compensated for lamp failure
D
Temperature- and voltage-compensated frequency
D
Warning indication of lamp failure by means of
frequency doubling
D
Relay output with high-current carrying capacity and
low saturation voltage
Figure 1. Application circuit as a car flasher
(Resistor R
1
, R
2
and R
t
: 1/4 Watt
R
1
for protection against continuous reversed polarity: 2 Watt)
Order Information
Extended Type Number
U243B
U243B-FP
Package
8 pin dual-inline plastic
8 pin SO plastic
Remarks
TELEFUNKEN Semiconductors
Rev. A1, 05-Sep-96
1 (6)
Preliminary Information
U243B
Circuit Description
The application circuit shows the operation of the U243B
as a car-direction indicator signal generator. The flashing
frequency is determined by the components R
t
and C
t
, and
the frequency can be calculated from
f
1
The use of this application circuit ensures damage and
interference protection accordance to VDE 0839. The
recognition point for lamp failure can be calculated from
the control signal threshold, typically 81 mV with
V
S
= 12 V.
1
R
t
C
t
1.5
(Hz)
where f
1
is the frequency in normal flashing operation
(basic frequency). The control frequency f
2
is typically
2.2 times the value of f
1
and is the frequency in the case
of lamp failure. The bright periods for f
1
and f
2
are inter-
nally set in the IC and are 50% for f
1
and 40% for f
2
.
The resistors R
1
and R
2
are needed to protect the circuit
against possible damage. An integrated Z-diode in addi-
tion to these external resistors limits the impulse current
in the integrated circuit to
≤
1.5 A. Connecting the circuit
with the wrong polarity leads to current limitation by R
1
,
R
2
and the resistance of the coil of the relay. A current of
about 150 mA would then flow over R
1
, so that for unlim-
ited protection against continuous reversal of the polarity
of the supply, a 2-W resistor would be necessary. A short
circuit between the indicator lamp (49a) and ground (31)
can give rise to a voltage drop of about 4 V across the
measuring resistance, R
3
. The circuit is not damaged by
such a short circuit.
With 81 mV and a measuring resistance of R
3
= 30 m
W
,
it corresponds to a lamp current of 2.7 A, i.e., the
frequency change-over with a lamp load of 21 W
+ 11.4 W. The variation of the control-signal threshold
with the supply voltage takes into account the PTC char-
acteristic of the filament lamps. A resistance R
p
≥
5 k
W
between the lamp indicator (49a) and ground (31) ensures
that in case the direction indicator switch is open, the
flashing generator is in stand-by mode.
With a control lamp of max. 4 W between 49 and 49a the
IC still starts with the bright phase.
The arrangement of the supply connections to Pins 2 and
6 must be such as to ensure that, on the connection PCB,
the resistance of V
S
to Pin 6 is lower than that to Pin 2.
Defined operation is ensured with a lamp load of
P
L
10 W or more. Defined operation with lamp loads
≥
2 W require an additional external resistance as
described in “Applications”. With considerably reduced
external circuitry, the integrated circuit U243B can be
used as an instable multivibrator in the frequency range
f = 0.05 to 10 Hz.
Absolute Maximum Ratings
Reference point Pin 1
Parameters
Supply voltage
Surge forward current
t
p
= 0.1 ms
t
p
= 2 ms
t
p
= 2 ms
Output current
Power dissipation
T
amb
= 95°C
T
amb
= 60°C
Junction temperature
Ambient temperature range
Storage temperature range
Pins 2 and 6
Pins 2 and 6
Pins 2 and 6
Pin 8
Pin 3
DIP8
SO8
DIP8
SO8
Symbol
V
S
I
FSM
I
FSM
I
FSM
I
o
P
tot
P
tot
P
tot
P
tot
T
j
T
amb
T
stg
Value
16.5
1.5
1.0
50
0.3
420
340
690
560
150
–40 to +95
–55 to +125
Unit
V
A
A
mA
A
mW
mW
mW
mW
°C
°C
°C
2 (6)
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A1, 05-Sep-96
U243B
Electrical Characteristics
Typical values under normal operation in application circuit figure 1, V
S
(+49, Pins 2 and 6) = 12 V
Reference point ground (–31), T
amb
= 25°C, unless otherwise specified
Parameters
Test Conditions / Pin
Supply voltage range
Pins 2 and 6
Supply current,
Pins 2 and 6
dark phase or stand-by
Supply current,
Pins 2 and 6
bright phase
Z–diode limitation
I
S2, 6
= 70 mA
Pins 2 and 6
Relay output,
saturation voltage
I
0
= 150 mA, V
S
= 9 V
Pin 3
Relay output,
Pin 3
reverse current
Relay coil resistance
Start delay
(first bright phase)
Frequency-determining
resistor
Frequency-determining
capacitor
Frequency tolerance (normal flashing, basic frequency
f
1
not including the tolerance of the external compo-
nents R
1
and C
t
)
Bright period
(basic frequency f
1
)
Bright period
(control frequency f
2
)
Frequency increase
(lamp failure)
Control-signal threshold
V
S
= 15 V
Pin 7
V
S
= 9 V
Pin 7
V
S
= 12 V
Pin 7
Transfer resistance
49a to common for
stand-by
Lamp load
Symbol
V
S
(+49)
I
S
I
S
V
S
Min
Typ
9 ... 15
4.5
7.0
23
Max
Unit
V
mA
mA
V
8
11
V
O
I
O
R
L
t
on
R
t
C
t
∆f
1
∆f
1
∆f
2
f
2
V
R3
V
R3
V
R3
R
P
P
L
10
6.8
1.0
0.1
60
10
510
47
V
mA
W
ms
k
W
m
F
%
%
%
–5
47
37
2.15 f
1
85
66
76
91
71
81
2
+5
53
45
2.3f
1
97
76
87
5
mV
mV
mV
k
W
W
Applications
D
Flashing generator, operation with smaller loads
(≥ 2 W)
By adding a resistor to the application circuit (figure 1),
defined operation with lamp loads
≥
2 W is possible. The
voltage drop across the resistor R
4
is generated by the
current flowing over the relay and should be about 15 mV.
With a relay current of 150 mA (relay resistance 73 Q),
this requires a resistance of R
4
= 100 m
W
. The change of
TELEFUNKEN Semiconductors
Rev. A1, 05-Sep-96
the operating point by 15 mV results in a corresponding
change of the control signal threshold by 15 mV. For a
lamp current of 2.7 A, a measuring resistance of
R
3
=
81 mV – 15 mV
2.7 A
= 25 m
W
results.
3 (6)
Preliminary Information
U243B
D
Istable multivibrator
The figure shows the minimum of circuitry necessary for
the operation as an instable multivibrator. The circuit is
suitable for frequencies between 0.05 Hz and approxi-
mately 10 kHz. The frequency can be calculated by using
the relationship for f
1
given in circuit description. A start-
ing resistor of 3.8 k
W
is integrated into the circuit between
pins 8 and 6. This means that, for a load on pin 3 of, for
example, 500
W
(open circuits) and zero current, a voltage
of about 1.4 V remains on the load (for 70
WW
the
corresponding voltage is about 220 mV). A load of R
L
≤
3.3 k
W
on pin 3 ensures correct operation of the instable
multivibrator. The relationship between the on- and off-
periods can be changed in this circuit by inserting a
resistor-diode combination parallel to R
1
(see dashed
lines in the figure), e.g., to reduce the “bright”-time.
Figure 2. Flashing generator with small loads
Figure 3. Instable multivibrator for general-purpose applications
Pin Description
Pin
1
2
3
4
Function
IC ground
Supply voltage V
S
Relay driver
C
t
oscillator
Pin
5
6
7
8
Function
R
t
oscillator
Supply voltage V
S
Lamp-failure detection
Start input (49a)
4 (6)
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A1, 05-Sep-96
U243B
Dimensions in mm
Package: DIP8
Package: SO8 (SOT96A)
TELEFUNKEN Semiconductors
Rev. A1, 05-Sep-96
5 (6)
Preliminary Information
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