U6433B_05 Datasheet, PDF (5/8 Pages) ATMEL Corporation – Flasher, 18-m Shunt, Frequency Doubling Disabling

U6433B
3.6.2
Control Signal Threshold 2 (8-mV Comparator K4)
A voltage drop between 49 mV to 8 mV at R₃ shunt resistor lets the flasher work in frequency
doubling mode.
If the voltage drop decreases to a value below V_R3MAX = 8 mV, frequency doubling is disabled.
This can be achieved either with a switch which bypasses the shunt resistor (for example, a spe-
cial hazard warning switch) or with a small lamp load.
The arrangement of the supply connections to pins 2 and 6 must ensure that, on the connection
PCB, the layer resistance from V_S to pin 6 is lower than the resistance to pin 2.
Flasher operation starts with a lamp load of P_L ≥ 1W.
3.7 Pin 8, Start Input
Start condition for flashing: the voltage at pin 8 has to be below the K3 threshold (flasher switch
closed).
Humidity and dirt may decrease the resistance between 49a and GND. If this leakage resistance
is > 5 kΩ, the IC is still kept in its off condition. In this case the voltage at pin 8 is between the
thresholds of comparators K2 and K3.
During the bright phase the voltage at pin 8 is above the K2 threshold; during the dark phase it is
below the K3 threshold.
For proper start conditions, a minimum lamp wattage of 1W is required.
4. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Reference point pin 1.
Parameters
Symbol
Value
Unit
Supply voltage, pins 2 and 6
Surge forward current
t_p = 0.1 ms, pins 2 and 6
t_p = 300 ms, pins 2 and 6
t_p = 300 ms, pin 8
Output current, pin 3
Power dissipation
T_amb = 95°C, SO8
T_amb = 60°C, SO8
Junction temperature
Ambient temperature range
Storage temperature range
V_S
18
V
I_FSM
1.5
1.0
A
A
30.0
mA
I_O
0.3
A
P_tot
340
mW
560
mW
T_j
150
°C
T_amb
–40 to +105
°C
T_stg
–55 to +150
°C
5. Thermal Resistance
Parameters
Junction ambient SO8
Symbol
R_thJA
Value
160
Unit
K/W
5
4810B–AUTO–10/05