Document
Features
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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 Minimum Lamp Load for Flasher Operation ≥ 1W Load-dump Protection Very Low Susceptibility to EMI Protection According to ISO/TR 7637/1 Level 4
1. Description
The design of the U6433B is similar to that of U6043B, both devices have the same excellent EMC (Electro Magnetic Capability) and protection features. The U6433B includes 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 especially important with respect to the US automotive industry. During direction mode the U6433B works like other flashers, that is, frequency doubling in the case of lamp outage. www.DataSheet4U.com
Flasher, 18-mΩ Shunt, Frequency Doubling Disabling U6433B
Rev. 4810B–AUTO–10/05
Figure 1-1.
Block Diagram
6
G5
2 + K1 + K4 VS - 8 mV VS - 49 mV
VS
C1 4.7 µF + K5 G4 5 G2
D1 23 V
R1 82 kΩ
4
VS - 4 V K2
K3
49 a
VS - 6 V 3 7
VS - 8 V 8 1
Shunt VS R3
R4 470 Ω
18 mΩ
R2 PL >1 W 1.5 kΩ
2
U6433B
4810B–AUTO–10/05
U6433B
2. Pin Configuration
Figure 2-1. Pinning SO8
GND
1
8
SI
VS
2
7
LD
U6433B
REL 3 6 VS
OSC
4
5
OSC
Table 2-1.
Pin 1 2 3 4 5 6 7 8
Pin Description
Symbol GND VS REL OSC OSC VS LD SI Function IC ground Supply voltage Relay driver Oscillator Oscillator Supply voltage Lamp failure detection Start input (49a)
3
4810B–AUTO–10/05
3. Functional Description
3.1 Pin 1, GND
The integrated circuit is protected against damage via resistor R4 to ground (–31) in the case of battery reversal. An integrated protection circuit together with external resistances R2 and R4 limits the current pulses in the IC.
3.2
Pin 2, Supply Voltage, VS – Power
The arrangement of the supply connections to pin 2 must be so as to ensure that, on the connection printed circuit board (PCB), the resistance of VS to pin 6 is lower than that to pin 2.
3.3
Pin 3, Relay Control Output (Driver)
The relay control output is a high-side driver with a low saturation voltage and is capable of driving a typical automotive relay with a minimum coil resistance of 60Ω.
3.4
Pins 4 and 5, Oscillator
The flashing frequency, f1, is determined by the R1C1 components as follows (see Figure 1-1 on page 2):
1 - Hz f 1 ≈ -----------------------------------R 1 × C 1 × 1.5
where C1 ≤ 47 µF R1 + 6.8 kΩ to 510 kΩ In the case of a lamp outage (see pin 7) the oscillator frequency is switched to the lamp outage frequency f2 with f2 ≈ 2.2 × f1. Duty cycle in normal flashing mode: 50% Duty cycle in lamp outage mode: 40% (bright phase)
3.5
Pin 6, Supply Voltage, Sense
For accurate monitoring via the shunt resistor, a minimized layer resistance from point VS/shunt to pin 6 is recommended.
3.6
3.6.1
Pin 7, Lamp Outage Detection
Control Signal Threshold 1 (49-mV Comparator K1) The detection point for lamp failure can be calculated from the control signal threshold, typically 49 mV with VS = 12V. With a measuring resistance of R3 = 18 mΩ, the frequency change-over is reached at a lamp load of 21W + 11.4W. The variation of the control signal threshold supply voltage takes into account the PTC characteristic of filament lamps.
4
U6433B
4810B–AUTO–10/05
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 VR3MAX = 8 mV, frequency doubling is disabled. This can be achieved either with a switch which bypasses the shunt resistor (for example, a special 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 VS to pin 6 is lower than the resistance to pin 2. Flasher operation starts with a lamp load of PL ≥ 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 ind.