U644B
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
1 (6)
Flasher, 18-m
W Shunt, Extremly Low Current Consumption
Description
The bipolar integrated circuit, U644B, is used in relay-
controlled automotive flashers where a high level EMC
is required. Lamp outage is indicated by frequency doub-
ling during hazard warning as well as direction mode.
If the flasher module provides an 4-pin connector the
control pin of U644B (Pin 6) can be used to operate the
IC in an extremly low-current mode.
Features
D Frequency doubling indicates lamp outage
D Frequency independent of temperature and voltage
change
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 TR7637/1 level 4
D Control input (Kl 15)
Ordering Information
Extended Type Number
Package
Remarks
U644B
DIP8
U644B-FP
SO8
Block Diagram
V
S
49 mV
Pulse
generator
GND
20 k
W
3.3 k
W
Relay
7
15
49 a
4
5
K
2
K
1
K
3
C
1
R
1
2
12707
R
3
49 a
Comparator K
2
49 a
Comparator K
3
2 k
W
20 k
W
20 k
W
20 k
W
13 k
W
30 V
6
3
8
1
Shunt
R
4
GND
31
R
5
10 k
W
30
18 m
W
Measuring
comparator K
1
220
W
R
2
Figure 1. Application circuit as a car flasher with control input
Resistor R
1
, R
2
and R
3
: 1/4 Watt
R
2
for protection against continuous reversed polarity: 1 Watt
U644B
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
2 (6)
Pulse
generator
GND
20 k
W
3.3 k
W
Relay
7
+V
S
49 a
4
5
K
2
K
1
K
3
C
1
R
1
2
12708
R
3
49 a
Comparator K
2
49 a
Comparator K
3
2 k
W
20 k
W
20 k
W
20 k
13 k
W
30 V
6
3
8
1
Shunt
R
4
GND
31
+49
18 m
W
V
S
49 mV
Measuring
comparator K
1
220
W
R
2
Figure 2. Application circuit as a car flasher without control input
Resistor R
1
, R
2
and R
3
: 1/4 Watt
R
2
for protection against continuous reversed polarity: 1 Watt
Application Note
In figure 1, the control input (Pin 6) is used to enable or disable U644B. If the ignition is switched off, the current
consumption is less than 50
mA.
In figure 2, Pin 6 is bridged to Pin 2, so U644B works like U6043B. Note that the resistor values of R
2
and R
3
are
different from the U6043B (see application circuit).
Pin Description
Pin
Symbol
Function
1
GND
IC ground
2
V
S
Supply voltage V
S
3
REL
Relay driver
4
OSC
C
1
Oscillator
5
OSC
R
1
Oscillator
6
V
S
Supply voltage / or control input
7
LD
Lamp failure detection
8
SI
Start input (49a)
1
2
3
4
8
7
6
5
GND
REL
OSC
SI
LD
Vs
OSC
U644B
V
S
13297
Figure 3. Pinning
U644B
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
3 (6)
Functional Description
Pin 1, GND
The integrated circuit is protected against damage via
resistor R
2
to ground (31) in the case of battery reversal.
An integrated protection circuit and the external
resistances R
1
and R
2
limit the ac-current pulse in the IC.
Pin 2, Supply voltage, V
S
- Power
Connected directly to battery (Kl 30).
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.
An integrated overvoltage detection disables the output at
V
S
[ 20 V to protect the lamps during jump start
Pin 4 and 5 Oscillator
Flashing frequency, f
1
, is determined by the R
1
C
1
components as follows (see figure 1):
f
1
[
1
R
1
C
1
1.5
Hz
where
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, control input
When the IC is powered by the battery Pin 6 is the control
input to switch the IC to zero current consumption during
stand-by.
Pin 7, Lamp outage detection
The lamp current is monitored via an external shunt
resistor R
4
and an internal comparator K1 with its
reference voltage of typ. 49 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
sh
= V
T
(K1) / I
outage
R
sh
= 49 mV/2.7 A = 18 m
W.
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 shortet 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.
Absolute Maximum Ratings
Reference point Pin 1
Parameters
Symbol
Value
Unit
Supply voltage
Pin 2
V
S
18
V
Surge forward current
t
P
= 0.1 ms
Pin 2
t
P
= 300 ms
Pin 2
t
P
= 300 ms
Pin 8
I
FSM
I
FSM
I
FSM
1.5
1.0
50
A
A
mA
Output current
Pin 3
I
O
0.3
A
Power dissipation
T
amb
= 120
C
DIP8
T
amb
= 105
C
SO8
T
amb
=
60
C
DIP8
T
amb
=
60
C
SO8
P
tot
P
tot
P
tot
P
tot
230
300
690
560
mW
mW
mW
mW
U644B
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
4 (6)
Absolute Maximum Ratings (continued)
Parameters
Symbol
Value
Unit
Junction temperature
T
j
150
C
Ambient temperature range
DIP8
SO8
T
amb
T
amb
40 to +120
40 to +105
C
C
Storage temperature range
T
stg
55 to +150
C
Thermal Resistance
Parameters
Symbol
Value
Unit
Junction ambient
DIP8
SO8
R
thJA
R
thJA
110
160
K/W
K/W
Electrical Characteristics
Typical values under normal operation in application circuit figure 1, V
S
(+49, Pin 2) = 12 V.
Reference point ground (31), T
amb
= 25
C unless otherwise specified
Parameters
Test Conditions / Pin
Symbol
Min.
Typ.
Max.
Unit
Supply voltage range
Pin 2
V
S
(+49)
8 to 18
V
Supply current
Dark phase or
stand-by
Pin 2
I
S
5
7
mA
Supply current
Bright phase
Pin 2
I
S
6
10
mA
Relay output,
saturation voltage
I
O =
300 mA
Pin 3
V
O
1.3
V
Relay output,
reverse current
Pin 3
I
O
0.1
mA
Relay coil resistance
R
L
60
W
Relay output overvoltage
detection (relay disabled)
19.0
20.2
22.5
V
Start delay
(first bright phase)
t
on
10
ms
Frequency determining
resistor
R
1
6.8
510
k
W
Frequency determining
capacitor
C
1
47
mF
Frequency tolerance (normal flashing, basic frequency
f
1
not including the tolerance of the external compo-
nents R
1
and C
1
)
f
1
6.5
+ 6.5
%
Bright period (basic frequency f
1
)
f
1
45
55
%
Bright period (control frequency f
2
)
f
2
35
45
%
Frequency increase (lamp failure)
f
2
2.1
f
1
2.4
f
1
Hz
Control signal threshold
V
s
= 18 V
Pin 7
V
s
= 8 V
Pin 7
V
s
= 13.5 V
Pin 7
V
R3
V
R3
V
R3
53
40.5
47.5
57
43.6
51
61
46.6
54.5
mV
mV
mV
Resistance between 49a to ground for stand-by
R
P
2
5.6
k
W
Lamp load
P
L
1
W
U644B
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
5 (6)
Package Information
13021
9.8
9.5
Package DIP8
Dimensions in mm
1.64
1.44
4.8 max
0.5 min
3.3
0.58
0.48
7.62
2.54
6.4 max
0.36 max
9.8
8.2
7.77
7.47
8
5
1
4
technical drawings
according to DIN
specifications
13034
technical drawings
according to DIN
specifications
Package SO8
Dimensions in mm
5.00
4.85
0.4
1.27
3.81
1.4
0.25
0.10
5.2
4.8
3.7
3.8
6.15
5.85
0.2
8
5
8
5
U644B
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
6 (6)
Ozone Depleting Substances Policy Statement
It is the policy of TEMIC TELEFUNKEN microelectronic 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 ).
The Montreal Protocol ( 1987 ) and its London Amendments ( 1990 ) intend to severely restrict the use of ODSs and
forbid their use within the next ten years. Various national and international initiatives are pressing for an earlier ban
on these substances.
TEMIC TELEFUNKEN microelectronic GmbH semiconductor division has been able to use its policy of
continuous improvements to eliminate the use of ODSs listed in the following documents.
1. Annex A, B and list of transitional substances of the Montreal Protocol and the London Amendments respectively
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.
TEMIC can certify that our semiconductors are not manufactured with ozone depleting substances and do not contain
such substances.
We reserve the right to make changes to improve technical design and may do so without further notice.
Parameters can vary in different applications. All operating parameters must be validated for each customer
application by the customer. Should the buyer use TEMIC products for any unintended or unauthorized
application, the buyer shall indemnify TEMIC against all claims, costs, damages, and expenses, arising out of,
directly or indirectly, any claim of personal damage, injury or death associated with such unintended or
unauthorized use.
TEMIC TELEFUNKEN microelectronic GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany
Telephone: 49 ( 0 ) 7131 67 2831, Fax number: 49 ( 0 ) 7131 67 2423
PDF 
ZIP