U243B
| Model | U243B |
| Description | Warning or Car-Direction Indicator |
| PDF file | Total 6 pages (File size: 91K) |
| Chip Manufacturer | TEMIC |
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
