U643B
Flasher, 30-mW Shunt
Description
The bipolar integrated circuit U643B 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.
Features
D
Temperature and supply voltage compensated
flashing frequency
D
Frequency doubling indicates lamp outage
D
Relay driver output with high current
carrying capacity and low saturation voltage
D
Minimum lamp load for flasher operation:
≥
1 W
D
Very low susceptibility to EMI
D
Protection according to ISO/TR 7637/1 level 4
Block Diagram
+ V
S
+ 49
6
C
1
4
Measuring comparator K
1
V
6
–81 mV
20 kW
K
1
2
R
3
Shunt
5 kW
7
30 mW
K
2
R
1
Pulse
generator
3
49 a–Comparator K
2
20 kW
49 a–Comparator K
3
K
3
23 V
20 kW
5 kW
IC Ground
1
95 9756
Relay
8
R
2
49 a
1.5...2.2 kW
5
R
4
470
W
5 W 21 W 21 W
21 W 21 W 5 W
Indicator lamps
GND
– 31
Figure 1. Application circuit as a car flasher, Resistor R
1
and R
2
: 1/4 Watt
R
4
for protection against continuous reversed polarity: 0.5 Watt
Ordering Information
Extended Type Number
U643B
U643B-FP
Package
DIP8
SO8
Remarks
Rev. A2, 21-Aug-00
1 (5)
U643B
Pin Description
Pin
1
2
3
4
5
6
7
8
Symbol
GND
V
S
REL
OSC
OSC
V
S
LD
SI
IC ground
Supply voltage V
S
Relay driver
C
1
Oscillator
R
1
Oscillator
Supply voltage V
S
Lamp failure detection
Start input (49a)
Figure 2. Pinning
OSC
REL 3
4
V
S
2
7
LD
Function
GND 1
8
SI
U643B
6
Vs
5
OSC
94 9290
Functional Description
Pin 1,
GND
The integrated circuit is protected against damage via
resistor R
4
to ground (–31) in the case of battery reversal.
An integrated protection circuit together with external
resistances R
2
and R
4
limits the current pulses in the IC.
Pin 2,
Supply voltage, V
S
- 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 V
S
to Pin 6 is lower than
that to Pin 2.
Pin 3,
Relay control output (driver)
The relay control output is a high-side driver with a low
saturation voltage and capable to drive a typical automo-
tive relay with a minimum coil resistance of 60
W.
Pin 4 and 5
Oscillator
Flashing frequency, f
1
, is determined by the R
1
C
1
compo-
nents as follows (see figure 1):
f
1
[
where
1
C
1
Hz
mized layer resistance from point V
S
/ shunt to Pin 6 is
recommended.
Pin 7,
Lamp outage detection
The lamp current is monitored via an external shunt
resistor R
3
and an internal comparator K1 with its
reference voltage of typ. 81 mV (V
S
= 12 V). The outage
of one lamp out of two lamps is detected according to the
following calculation:
Nominal current of 1 lamp: 21 W / (V
S
= 12 V):
I
lamp
= 1.75 A
Nominal current of 2 lamps: 2 x 21 W / (V
S
= 12 V):
I
lamp
= 3.5 A.
The detection threshold is recommended to be set in the
middle of the current range: I
outage
[
2.7 A
Thus the shunt resistor is calculated as:
R
3
= V
T
(K1) / I
outage
R
3
= 81 mV/2.7 A = 30 mW.
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 the case
of shorted lamps.
Pin 8,
Start input
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
49 a and GND. If this leakage resistance is
u
5 kW 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 1 W is required.
R
1
1.5
C
1
47
mF
R
1
+
6.8 kW to 510 kW
In the case of a lamp outage (see Pin 7) the oscillator
frequency is switched to the lamp outage frequency f
2
with f
2
[
2.2
f
1
.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode: 40% (bright phase)
Pin 6,
Supply voltage, Sense
For accurate monitoring via the shunt resistor, a mini-
2 (5)
Rev. A2, 21-Aug-00
U643B
Absolute Maximum Ratings
Reference point Pin 1
Parameters
Supply voltage
Surge forward current
t
P
= 0.1 ms Pin 2 and 6
t
P
= 300 ms Pin 2 and 6
t
P
= 300 ms Pin 8
Output current
Pin 3
Power dissipation
T
amb
= 95°C
T
amb
= 60°C
Junction temperature
Ambient temperature range
Storage temperature range
DIP 8
SO 8
DIP 8
SO 8
P
tot
P
tot
P
tot
P
tot
T
J
T
amb
T
stg
420
340
690
560
150
–40 ... + 95
–55 ... + 150
mW
mW
mW
mW
°C
°C
°C
I
FSM
I
FSM
I
FSM
I
O
1.5
1.0
50
0.3
A
A
mA
A
Pin 2 and 6
Symbol
V
S
Value
16.5
Unit
V
Thermal Resistance
Parameters
Junction ambient
DIP8
SO8
Symbol
R
thJA
R
thJA
Value
110
160
Unit
K/W
K/W
Electrical Characteristics
Typical values under normal operation in application circuit (see figure 1), V
S
(+49, Pin 2 and 6) = 12 V.
Reference point ground (–31), T
amb
= 25°C, unless otherwise specified
Parameters
Supply voltage range
Supply current:
Dark phase
Bright phase
Relay output:
saturation voltage
reverse current
Start delay
Frequency tolerance
Bright period
Frequency increase
Control signal threshold
Basic frequency f
1
Control frequency f
2
Lamp outage
V
S
= 15 V
V
S
= 9 V
V
S
= 12 V
49a to GND
Pin 7
Pin 7
Pin 7
First bright phase
Pin 3
I
O
= 150 mA, V
S
= 9 V
with resistance = 60
W
Test Conditions / Pins
Pin 2 and 6
Pin 2 and 6
I
S
I
S
4.5
7.0
8
11
mA
mA
Symbol
V
S
(+49)
Min.
Typ.
9 to 15
Max.
Unit
V
V
O
I
O
t
on
df
1
∆f
1
∆f
2
f
2
V
R3
V
R3
V
R3
R
P
P
L
1
–5
47
37
2.15 f
1
85
66
76
91
71
81
4
1.0
0.1
10
+5
53
45
2.3 f
1
97
76
87
5
V
mA
ms
%
%
%
Hz
mV
mV
mV
kW
W
Leakage resistance
Lamp load
Rev. A2, 21-Aug-00
3 (5)
U643B
Package Information
Package DIP8
Dimensions in mm
9.8
9.5
1.64
1.44
7.77
7.47
4.8 max
6.4 max
0.5 min
0.58
0.48
7.62
8
5
2.54
3.3
0.36 max
9.8
8.2
technical drawings
according to DIN
specifications
13021
1
4
Package SO8
Dimensions in mm
5.00
4.85
1.4
0.4
1.27
3.81
8
5
0.25
0.10
0.2
3.8
6.15
5.85
5.2
4.8
3.7
technical drawings
according to DIN
specifications
13034
1
4
4 (5)
Rev. A2, 21-Aug-00
U643B
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TEMIC Semiconductor GmbH
to
1. Meet all present and future national and international statutory requirements.
2. Regularly and continuously improve the performance of our products, processes, distribution and operating systems
with respect to their impact on the health and safety of our employees and the public, as well as their impact on
the environment.
It is particular concern to control or eliminate releases of those substances into the atmosphere which are known as
ozone depleting substances (ODSs).
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their use within the next ten years. Various national and international initiatives are pressing for an earlier ban on these
substances.
TEMIC Semiconductor GmbH
has been able to use its policy of continuous improvements to eliminate the use of
ODSs listed in the following documents.
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2. Class I and II ozone depleting substances in the Clean Air Act Amendments of 1990 by the Environmental
Protection Agency (EPA) in the USA
3. Council Decision 88/540/EEC and 91/690/EEC Annex A, B and C (transitional substances) respectively.
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can certify that our semiconductors are not manufactured with ozone depleting
substances and do not contain such substances.
1.
We reserve the right to make changes to improve technical design and may do so without further notice.
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and expenses, arising out of, directly or indirectly, any claim of personal damage, injury or death associated with
such unintended or unauthorized use.
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TEMIC Semiconductor GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany
Telephone: 49 (0)7131 67 2594, Fax number: 49 (0)7131 67 2423
Rev. A2, 21-Aug-00
5 (5)
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