Features

• Temperature and Supply Voltage Compensated Flashing Frequency

• Frequency Doubling Indicates Lamp Outage
• Relay Driver Output with High Current Carrying Capacity and Low Saturation Voltage
• Minimum Lamp Load for Flasher Operation: ≥ 1 W
• Very Low Susceptibility to EMI
• Protection According to ISO/TR 7637/1 Level 4
Flasher IC with
18-mΩ Shunt

U6043B
1. Description
The bipolar integrated circuit U6043B is used in relay-controlled automotive flashers
where a high level EMC is required.
Lamp outage is indicated by frequency doubling during hazard warning as well as
direction mode.

Rev. 4726B–AUTO–11/05
2. Block Diagram
Figure 2-1. Car Flasher Application Circuit

+ VS

+ 49
6 2
C1 R3
Measuring comparator 18 mΩ
Shunt
V 6 - 49 mV
4 20 kΩ 5 kΩ
K1 7

K2
Pulse 3
R1
generator
49 a-Comparator K 2
Relay
20 kΩ
49 a-Comparator K 3 8 R2
49 a
K3 1.5...2.2 kΩ
5 23 V

20 kΩ 5 kΩ

IC Ground

1
R4

470 Ω 5 W 21 W 21 W 21 W 21 W 5 W
Indicator lamps
GND
- 31

2 U6043B
4726B–AUTO–11/05
 U6043B
3. Pin Configuration
Figure 3-1. Pinning

GND 1 8 SI

VS 2 7 LD
U6043B
REL 3 6 VS

OSC 4 5 OSC

Table 3-1. Pin Description

Pin Symbol Function
1 GND IC ground
2 VS Supply voltage
3 REL Relay driver
4 OSC Oscillator
5 OSC Oscillator
6 VS Supply voltage, Sense
7 LD Lamp outage detection
8 SI Start input (49a)

4. Functional Description

4.1 Pin 1, GND

The U6043B is protected against damage in case of battery reversal via resistor R4 to ground
(-31). An integrated protection circuit together with external resistances R2 and R4 limits the cur-
rent pulses in the IC.

4.2 Pin 2, Supply Voltage, VS power

The arrangement of the supply connections to Pin 2 (and 6) 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.

4.3 Pin 3, Relay Control Output (Driver)

The relay control output is a high-side driver with a low saturation voltage. It is capable of driving
a typical automotive relay with a minimum coil resistance of 60 Ω.

3
4726B–AUTO–11/05
4.4 Pin 4 and 5, Oscillator
The flashing frequency, f1, is determined by the R1C1 components as given by the following for-
mula below (see Figure 2-1):

1
≈ ------------------------------------- Hz
1 R 1 × C 1 × 1,5

where C1 ≤47 µF, R1 = 6.8 kΩ to 510 kΩ

In case of a lamp outage (see Pin 7) the oscillator frequency is switched to the lamp outage fre-
quency f2 with f2 ≈ 2.2 × f1.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode: 40% (bright phase)

4.5 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.

4.6 Pin 7, Lamp Outage Detection

The lamp current is monitored via an external shunt resistor Rsh and an internal comparator K1
with its reference voltage of typically 49 mV (VS = 12 V). The outage of one lamp is detected
according to the following calculation:
Nominal current of 1 lamp: 21 W/(VS = 12 V): Ilamp = 1.75 A
Nominal current of 2 lamps: 2 × 21 W/(VS = 12 V): Ilamp = 3.5 A
We recommend setting the detection threshold in the middle of the current range:
Ioutage ≈ 2.7 A
Thus, the shunt resistor is calculated as:
Rsh = VT (K1)/Ioutage
Rsh = 49 mV/2.7 A = 18 mΩ
Comparator K1's reference voltage is matched to the characteristics of filament lamps (see
"Control Signal Threshold" in the data part).
The combination of shunt resistor and resistance of wire harness prevents Pin 7 from a too high
voltage in case of shorted lamps.

4.7 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 49 a and GND. If this leakage resis-
tance is > 5 kΩ, the IC is still kept 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 1 W is required.

4 U6043B
4726B–AUTO–11/05
 U6043B

5. Absolute Maximum Ratings

Reference point Pin 1
Parameters Symbol Value Unit
Supply voltage Pin 2 and 6 VS 16.5 V
Surge Forward Current
tP = 0.1 ms Pin 2 and 6 IFSM 1.5 A
tP = 300 ms Pin 2 and 6 IFSM 1.0 A
tP = 300 ms Pin 8 IFSM 50 mA
Output current Pin 3 IO 0.3 A
Power Dissipation
Tamb = 95° C DIP8 Ptot 420 mW
SO8 Ptot 340 mW
Tamb = 60° C DIP8 Ptot 690 mW
SO8 Ptot 560 mW
Junction temperature TJ 150 °C
Ambient temperature range Tamb -40 to +95 °C
Storage temperature range Tstg -55 to +150 °C

6. Thermal Resistance
Parameters Symbol Value Unit
DIP8 RthJA 110 K/W
Junction ambient
SO8 RthJA 160 K/W

7. Electrical Characteristics
Typical values under normal operation in application circuit (see Figure 2-1), VS (+49, Pin 2 and 6) = 12 V.
Reference point ground (-31), Tamb = 25°C, unless otherwise specified.
Parameters Test Conditions Symbol Min. Typ. Max. Unit
Supply voltage range Pin 2 and 6 VS 9 15 V
Dark phase, Pin 2 and 6 IS 4.5 8 mA
Supply current
Bright phase, Pin 2 and 6 IS 7.0 11 mA
Relay control output: Pin 3
Saturation voltage IO = 150 mA, VS= 9 V VO 1.0 V
Reverse current IO 0.1 mA
Start delay (Delay time) First bright phase ton 10 ms
Frequency tolerance Normal flashing ∆f1 -5 +5 %
Basic frequency f1 ∆f1 47 53 %
Bright period
Control frequency f2 ∆f2 37 45 %
Frequency increase Lamp outage f2 2.15 × f1 2.3 × f1 Hz
VS = 15 V, Pin 7 VRs 50 53 57 mV
Control signal threshold VS = 9 V, Pin 7 VRs 43 45 47 mV
VS = 12 V, Pin 7 VRs 47 49 51 mV
Leakage resistance 49a to GND RP 4 5 kΩ
Lamp load PL 1 W

5
4726B–AUTO–11/05
8. Ordering Information
Extended Type Number Package Remarks
U6043B-MY DIP8 Pb-free
U6043B-MFPY SO8 Tubed, Pb-free
U6043B-MFPG3Y SO8 Taped and reeled, Pb-free

9. Package Information

6 U6043B
4726B–AUTO–11/05
 U6043B

Package SO8 5.2

Dimensions in mm 4.8
5.00
4.85 3.7

1.4

0.25 0.2
0.4 3.8
0.10
1.27 6.15
3.81 5.85

8 5

technical drawings
according to DIN
specifications

1 4

10. Revision History

Please note that the following page numbers referred to in this section refer to the specific revision
mentioned, not to this document.
Revision No. History
• Put datasheet in a new template
4726B-AUTO-11/05 • First page: Pb-free logo added
• Page 6: Ordering Information changed

7
4726B–AUTO–11/05
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