U643B-MFPG3Y Atmel, U643B-MFPG3Y Datasheet - Page 5

• Manufacturer Part Number: U643B-MFPG3Y
• Description: IC FLASHER 30M OHM SHUNT 8-SOIC
• Manufacturer: Atmel
• Type: Automotive, Flasherr

Specifications of U643B-MFPG3Y

• Current - Supply: 7mA
• Current - Output: 100µA
• Voltage - Supply: 9 V ~ 15 V
• Operating Temperature: -40°C ~ 95°C
• Package / Case: SO-8
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

4.6
4.7
4727B–AUTO–09/05
Pin 7, Lamp Outage Detection
Pin 8, Start Input
The lamp current is monitored via an external shunt resistor R
with its reference voltage of typically 81 mV (V
according to the following calculation:
Nominal current of 1 lamp: 21W / (V
Nominal current of 2 lamps: 2
The detection threshold should be set in the middle of the current range:
I
Thus, the shunt resistor is calculated as:
R
R
Comparator K1's reference voltage is matched to the characteristics of filament lamps (see Con-
trol Signal Threshold in
The combination of shunt resistor and resistance of wire harness prevents pin 7 from a too high
voltage in the case of shorted lamps.
Start condition for flashing: the voltage at pin 8 has to be below K3 threshold (flasher switch
closed).
Humidity and dirt may decrease the resistance between 49a and GND. If this leakage resistance
is > 5 k , the IC still remains in the 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.
outage
3
3
= V
= 81 mV/2.7A = 30 m
T
(K1) / I
2.7A
outage
“Electrical Characteristics” on page
21W / (V
S
= 12V): I
S
= 12V): I
lamp
S
= 12V). The outage of one lamp is detected
= 1.75A
lamp
= 3.5A.
6).
3
and an internal comparator K1
U643B
5