U2480B Datasheet, PDF (4/8 Pages) TEMIC Semiconductors – Automotive Lamp Outage Monitor

U2480B
Functional Description
Comparators
The voltage threshold of all internal comparators has a
typical value of V_th = 10 mV.
w A voltage drop accross the shunt of V_sh V_th means no
fault in the lamp circuit and the output is disabled.
v In the event of a voltage drop V_sh V_th, the output sup-
plies the current I_O, and the pilot lamp is activated by the
external transistor.
v ^{The output is reliably disabled for a voltage at the refer-}
ence pin of the comparators of V_minRef 1/3 V_S
The typical values of the input currents are 25 mA and are
equally large at the switch-over instant, thus making it
possible to connect protective resistors in series. The
internal threshold is independent of the value of the
protective resistor as long as all resistors of a comparator
have the same value.
Fuse Monitoring
It is possible to monitor the fuses of the lamp circuits by
means of an EXCLUSIVE OR function between K1 and
K3 and between K5 and K6.
If the Ref pin of K1 (orK5) is low and the Ref pin of K2
(or K6) is simultaneously high, or vice versa, a fault is
indicated.
Simultaneous failure of both fuses is not detected.
A fuse is faulty if the input voltage at the pin Ref falls
below the voltage V_minRef (1/3 V_S).
Time Delay
" A fault is indicated only if it is present for t_d = 1.2 0.2 s.
w If an OK pulse 100 ms occurs during this time, time
counting is reset to ”0”. An OK pulse is generated if the
comparators K1 to K8 and the input BL do not signal a
fault.
w ^{A periodic fault signal (period of less than 1 s) is indicated}
only if the mark-to-space ratio is 10/1, whereby the
pulse time corresponds to an item of fault information.
The time delay until the fault is indicated exceeds the time
t_d = 1.2 s in this case.
Storage
A failure in the break light circuit which is present for
longer than t_d is stored.
v A voltage of V_BL 0.15 V_S which is present at the input
BL for longer than t_d leads to fault indication with
storage. This allows the possibility of additional flashing
monitoring.
w v A voltage of V_BL 0.2 V_S and of V_BL 0.65 V_S which
is present at the input BL for longer than t_d leads to fault
indication without storage. It is thus possible to extend the
scope of monitoring beyond 11 lamps by means of
additional comparators ICs.
w A voltage of V_BL 0.7 V_S at the input BL does not cause
a fault signal.
The turn indicator and the brake light memory is
maintained by V_S (terminal 15)
Power-on Reset
When V_Batt (terminal 15) is applied to Pin V_S, a brief
signal is produced which generates the power-on reset. As
a result, the turn indicator, the brake light memory and the
counters are reset.
Outputs
A fault signal at the comparators K1 to K8 or at the
comparator Pin BL enables the output so that current I_O
can flow. The output blocking voltage (V_S – V_out) is
typically 1 V.
Threshold Testing without Time Delay t_d
To connect the input comparators directly to the output
pin, a voltage of 6 V at Pin OSC is necessary (omit R_OSC
and C_OSC).
Absolute Maximum Ratings
Parameters
Supply voltage
Pulse current (2 ms)
Short circuit current (reversed battery)
Output current
Ambient temperature range
Symbol
Value
Unit
V_S, V_Batt
16.5
V
I_S
1.1
A
I_SC
170
mA
I_out
–12
mA
T_amb
–40 to +100
°C
4 (8)
TELEFUNKEN Semiconductors
Rev. A1, 22-Oct-97