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U2481B Schematic ( PDF Datasheet ) - Temic

Teilenummer U2481B
Beschreibung (U2481B / U2482B) Automotive Lamp Outage Monitor
Hersteller Temic
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Gesamt 11 Seiten
U2481B Datasheet, Funktion
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)






U2481B Datasheet, Funktion
U2481B/ U2482B
www.DataSheet4U.com
Integrated Delay, Debouncing, Failure Dis-
play
As soon as a comparator detects a failure a slow upward
counter is started in order to generate the delay time,
tdel = 1.2 s. With a consistent failure the output stage is
enabled after tdel. If the failure disappears during tdel a fast
downward counter is started in order to generate the reset
time treset y 135 ms. The upward counter is reset, the
output stage stays disabled.
Benefits: Intermittent contacts in the wire harness do not
activate the pilot lamp! Even cyclical intermittent
contacts are screened out as long as the pulse/pause ratio
is smaller than 10:1. In the case of higher duty cycles the
upward counter may reach its trigger threshold for the
output activation after t > tdel.
Individual delay- and reset times can be adjusted with
external R/C components according to (see “oscillator”)
– tdel = 1930 x tosc
– treset = 198 x tosc
TELEFUNKEN Semiconductors
Latch for Brake Lamp Monitor
A failure of a brake lamp detected by comparator K7 or
a blown fuse in the brake circuitry is memorized after the
delay time has expired.
A reset of the latch can only be performed with a “power-
on-reset”.
Output Stage
The output is a Darlington stage stage with protection
diodes to VS and IC ground. The output is designed to
drive an external pilot lamp with an external PNP
transistor.
At the end of the delay time the output stage is switched
on and can source a current of Iout = –10 mA with a typical
saturation voltage of Vsat = 1 V.
Test Mode
With VTEST = 23 V (20 mA) applied to Pin osc, via a
200 W resistor the delay time stage can be bypassed for
test purposes. A failure detection will be displayed
immediately to save time during threshold testing.
6 (11)
Preliminary Information
Rev. A1: 21.08.1995

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