U243B Datasheet, PDF (4/6 Pages) TEMIC Semiconductors – Warning or Car-Direction Indicator

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
W ^{the relationship for f1 given in circuit description. A start-}
ing resistor of 3.8 k is integrated into the circuit between
pins 8 and 6. This means that, for a load on pin 3 of, for
W example, 500 (open circuits) and zero current, a voltage
WW of about 1.4 V remains on the load (for 70 the
corresponding voltage is about 220 mV). A load of R_L ≤
3.3 kW 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 R₁ (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
Function
1 IC ground
2 Supply voltage V_S
3 Relay driver
4 C_t oscillator
Pin
Function
5 R_t oscillator
6 Supply voltage V_S
7 Lamp-failure detection
8 Start input (49a)
4 (6)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A1, 05-Sep-96