U6433B-FP

The U6433B-FP has the following features including Temperature and voltage compensated frequency;Warning indication of lamp failure by means of frequency doubling can be disabled;Voltage dependence of the car indicator lamps compensated for lamp failure;Relay output with high current carrying capacity and low saturation voltage;Load-dump protection;RF protected;Damage and interference protection with a minimum of external components.

U6433B-FP's design is mainly based on the good results of U6043B in terms of EMC (Electro Magnetic Capability) and protection  features.  U6433B  contains  an  additional 8-mV comparator  and a logical connection with the frequency doubling stage. This combination can be used for a hazard switch which bypasses the external shunt resistor to disable the frequency doubling. This feature is a request of the US automotive industry. During direction mode U6433B works like other flashers, i.e., frequency doubling in the case of lamp outage.The resistors Rl and R2 are needed to protect the circuit against possible damage. An integrated protection circuit, together with these external resistors, limits the impulse current in the integrated circuit.Protection in the case of battery reversal: The resistors Rl,R2 and the relay coil limit the currents so the integrated circuit will not be damaged. To achieve a protection for continuous battery reversal, resistor Rl should be capable of 30 mA (0.5 W type).

A short circuit between indicator lamp (49a) and ground (31)of U6433B-FP can give rise to a voltage drop of about 4 V across the measuring resistance R3.In this case, the integrated circuit would not be damaged.The use of the application circuit (figure 1) ensures damage and interference protection consistent with ISOIfR 7637/1 and load dump.If the voltage drop of VR3MAX=8 mV falls the frequency doubling is disabled. U6433B-FP can be achieved either with a switch which by passes the shunt resistor (e.g., a special hazard warning switch) or with a small lamp load.