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PDF U2481B Data sheet ( Hoja de datos )
| Número de pieza | U2481B | |
| Descripción | (U2481B / U2482B) Automotive Lamp Outage Monitor | |
| Fabricantes | Temic | |
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TELEFUNKEN Semiconductors
www.DataSheet4U.com
Automotive Lamp Outage Monitor
U2481B/ U2482B
Description
The U2481B and the U2482B multicomparator circuits
are designed to monitor automotive illumination by
sensing the voltage drop across shunt resistors. Provided
with extremely low comparator thresholds, these ICs can
be used together as a chip set to build an entire lamp
monitor system. Single operation of both circuits is also
possible.
As a special feature for brake lamp monitoring, the
U2481B contains a latch stage connected to one of its
triple comparators.
With
– 4 single comparators
– 1 double comparator and
– 2 triple comparators
each of the integrated circuits monitors up to 12 lamps
and up to 6 fuses.
All comparator stages are combined together to control
the common output stage.
Features
D Extremely low comparator thresholds of typically
3.5 mV
D Internal compensation for copper shunts
D Internal compensation for voltage-dependent
bulb characteristic
D Comparator input voltage may exceed supply voltage
D Internal protection measures for pulses
according to ISO TR 7637/1
D ESD according to MIL-SID-883 C test method 3015.7
– Human body model: 4 kV
– Machine model:
200 V
EMI protection (TEM cell up to 100 V/m)
Benefits
D Extremely low threshold voltage gives low voltage
drop via shunt resistor. Power dissipation of the lamp
monitor module is minimized
D Perfect EMC in conjunction with an appropriate
pc board layout
Applications
Both ICs can be used in any kind of vehicle with a 12 V
supply. It is sufficient to insert small resistors into the
lamp wiring and to provide the dashboard instrument
cluster with a pilot lamp. These ICs increase the safety
and add comfort features.
Rev. A1: 21.08.1995
Preliminary Information
1 (11)
1 page  
TELEFUNKEN Semiconductors
www.DataSheet4U.com
Functional Description
Power Supply, Pins 19 and 20
The Ics have two supply pins. The IC itself is supplied via
Pin 19 (stabilized voltage, POR-circuitry). Pin 20
supplies only the current sources of the comparators. Both
pins have an an internal 21 V Zener Diode for protection.
For reasons of interference protection and surge
immunity the supply voltage pins have to be provided
with RC-circuitries as shown in figure... The resistors
limit the current in the case of overvoltage, whereas the
capacitors smooth the supply voltage.
Recommended values:
Pin 19:
R = 150 W; K = 0.1 mF
Pin 20:
R = 1000 W; K = 0.1 mF
An external diode protects the IC against battery reversal.
Power-On-Reset
When the supply voltage is switched on, a power-on-reset
pulse is generated internally which resets the brake lamp
monitor latch and the counter stages.
Oscillator, Pin 15
The RC-oscillator is the time base for clock 1 and clock 2
(see block diagram) which are desired from a divider
stage and fed to the two upward and downward counters.
The oscillator frequency fosc is mainly determined by the
external R/C components and an integrated resistor. The
capacitor K is charged by the external resistor and
discharged by the integrated one. Because of the temper-
ature characteristic and the tolerances of the integrated
2 kW-resistor, the external one has to have considerable
higher value in order to achieve a stable frequency.
Calculation of the frequency:
fosc
+
1
fosc
+
1
c osc
(0.74 Rosc ) 2260 W)
With the recommended values
Rosc = 82 kW and Cosc = 10 nF
fosc ≈ 1.58 kHz
Comparators
Comparators K1 and K2: threshold voltage of typically
Vth = 13 mV; designed to monitor high- and low-beam
bulbs, where the fuses can be used as shunt resistors.
Comparators K3 to K7: threshold voltage of typically
Vth = 3.5 mV; designed for all other monitor purposes.
Due to the integrated compensation circuitry, these
comparators are suitable for pc layer copper shunts.
U2481B/ U2482B
A bulb is detected as “good” as long as the voltage drop
via the shunt resistor exceeds the threshold voltage. The
pilot lamp is off. A failed bulb is detected if the voltage
drop via the shunt resistor is smaller than the threshold
voltage. The pilot lamp is on. An external transistor is
necessary to drive the pilot lamp.
In order to disable monitoring when the lamps are
switched off, therefore the comparator outputs are
disabled if the reference voltage Vref < VMin with
VMin = 0.33 VB.
As protection against transients on the supply, all
comparator inputs require external resistors. Their
tolerances directly influence the comparator threshold
accuracy. Resistors with a " 1% tolerance are
recommended.
Single comparators: The inputs (K1, K2, K4, K6) sink
currents of typically 10 mA each. During switch-over, the
currents of reference and input pins are identical.
Therefore identical external protection resistors
(R = 1 kW) are required.
Double comparator: The reference input (K5) sinks a
current of typically 20 mA; its inputs sink currents of
typically 10 mA each during switch-over. Therefore the
external protection resistors must provide R = 1 kW for
REFK5 and R = 2 kW each for IN1K5 and IN2K5.
Triple comparators: The reference inputs (K3 and K7)
sink currents of typically 30 mA. All inputs (IN1K3, IN2K3
IN3K3, and IN1K7, IN2K7, IN3K7) sink the identical typical
current of 10 mA during switch-over. Therefore the
external protection resistor must provide R = 1 kW for
REFK3 and REFK7 and R = 3 kW at each input.
Fuse Monitoring
The internal EXOR conjunction of comparators K1 and
K2 allows fuse monitoring for both lamps. Even a
simultaneous blowout of both fuses is detected.
The pins INFK3, INFK5 and INFK6 with their EXOR gates
can be used for additional fuse monitoring.
Detection threshold for a blown fuse is Vref < VMin with
VMin = 0.33 VB (VB = reference voltage of comparators).
Pin INF is used for brake fuse monitoring. With a voltage
drop VF > 4.8 V across the fuse, the comparator detects
a blown fuse. A voltage drop VF < 2.8 V represents a
“good” fuse. U2481B’s comparator K7 is connected to a
latch, thus a brake lamp outage is memorized.
Rev. A1: 21.08.1995
Preliminary Information
5 (11)
5 Page 
TELEFUNKEN Semiconductors
www.DataSheet4U.com
Ozone Depleting Substances Policy Statement
U2481B/ U2482B
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
Rev. A1: 21.08.1995
Preliminary Information
11 (11)
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet U2481B.PDF ] | |
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